MythBusters: Bullets Fired Straight Up


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MikeJackmin
December 21, 2005, 02:32 PM
Check out this excerpt from a recent interview (http://science.slashdot.org/science/05/12/21/1435208.shtml) with the MythBusters guys:

"We just worked on a myth called "bullets fired up" -- i.e., will a bullet fired directly vertically kill you when it comes back down. We did tons of research on it, and in the end, added significantly to the body of knowledge that's out there on the subject. I won't give away the ending, but we nailed this one."

All I know about this is what Hatcher wrote back in the 20s. Ought to be interesting...

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Sry0fcr
December 21, 2005, 02:37 PM
No doubt it can kill or wound you if you're hit. It's happened before.

gino
December 21, 2005, 02:52 PM
Nope, if you fire a gun straight up, it would be like dropping the bullet from a great height. The wind resistance would limit terminal velocity to a speed that would NOT kill you if you were hit by it.


Sort of like dropping a penney from the top of a tall building. The Mythbusters already did that one and showed that it would not hit hard enough to kill.

dolanp
December 21, 2005, 02:59 PM
Not that it matters, the odds of someone being able to point a gun in the precise position to allow the bullet to fall in the same spot are virtually nil.

The-Fly
December 21, 2005, 03:10 PM
Nope, if you fire a gun straight up, it would be like dropping the bullet from a great height. The wind resistance would limit terminal velocity to a speed that would NOT kill you if you were hit by it.


Sort of like dropping a penney from the top of a tall building. The Mythbusters already did that one and showed that it would not hit hard enough to kill.

i'd beg to differ. When i lived in LA (the city), every july 4th and new years lots of bangers would fire their guns into the air, and usually people would get hit by the bullets returning to ground, wounding and killing them. Think about it, a 100-200 grain bullet coming straight down is going to have a decent terminal velocity, probably several hundred miles per hour, and thats more then enough to penetrate the top of the head. Any engineer or physics majors want to work out the math on what the terminal velocity on a 9mm 147gr or .45 230 grain round would be ?

DevLcL
December 21, 2005, 03:13 PM
Nope, if you fire a gun straight up, it would be like dropping the bullet from a great height. The wind resistance would limit terminal velocity to a speed that would NOT kill you if you were hit by it.

Completely wrong. I know a man from pakistan that lost 3 sons all of which died from bullets hitting them in the top of the head going straing down.

-Dev

countertop
December 21, 2005, 03:23 PM
This analysis (http://www.loadammo.com/Topics/March01.htm) says it won't necessarily kill you but will cause a fairly disabling wound.

MrTuffPaws
December 21, 2005, 03:24 PM
Well after doing some google, I came up with this

http://www.loadammo.com/Topics/March01.htm

Out of the more than 500 shots fired from the test platform only 4 falling bullets struck the platform and one fell in the boat near the platform. One of the bullets striking the platform left a 1/16 inch deep mark in the soft pine board. The bullet struck base first.

Based on the results of these tests it was concluded that the bullet return velocity was about 300 f.p.s. For the 150 gr. bullet this corresponds to an energy of 30 foot pounds. Earlier the Army had determined that, on the average, it required 60 foot pounds of energy to produce a disabling wound. Based on this information, a falling 150 gr. service bullet would not be lethal, although it could produce a serious wound.

30ftlbs from a 30cal 150gr bullet can still wound you, and I bet that if it hit right, could kill you and easily kill a small child.

rero360
December 21, 2005, 03:27 PM
math isn't my strong point but I would say to fond out the results you determine the max altitude that the round would achieve, I know theres a formula for it but I'm not sure what it is, then you calculate the terminal velocity of the round seeing as how it would indeed be like the round dropping from said height, however I would bet that a bullet would have a higher terminal velocity than a penny due to its hevier weight and its better ballistic coeficient. then you just compare the terminal velocity of the round with the normal velocity and that'll give you a good idea of what the outcome would be. If I had to guess though, from watching various mythbuster episodes where they find the terminal velocity of given objects I would say that for any given bullet your going to be looking at a speed in excess of 100 mph, I'm thinking of about 150, seeing how an average person freefalls at 120mph and a penny is at 60 IIRC so if anyone can fingure it out I'm all ears.

Camp David
December 21, 2005, 03:32 PM
"Bullets Fired Straight Up" like "arrows fired straight up" leave their point of launch from a specific point on a rotating mass... It is impossible for them to return to that point, simply due to the fact that the mass is moving, 36,000mph... Said another way, the safest place to be after a bullet or arrow is fired "straight up" is exactly under point of launch. Wind, weight of bullet, velocity, and a whole host of other factors will also affect bullet or arrow after launch.

Red Tornado
December 21, 2005, 03:34 PM
It would depend on the bullet somewhat. A 29gr .22 or a 750gr .50cal at terminal velocity (call it 200 mph, or 300fps from MrTuffPaws source) are going to hit very differently. They'll fall backwards of course, so the bullet type wouldn't matter, as they'll hit base first.

I'll let someone drop a .22 short bullet on me, if someone will volunteer to stand under the fiddy cal. :evil:
RT

Edit: Rero, weight doesn't enter into the equation, just the ballistic coefficient.

Cosmoline
December 21, 2005, 03:36 PM
So which member of the build team took THAT one for the team, I wonder?

I always laugh when they put on their bit at the start saying "don't try this at home..." Yeah, I've long planned on building a LIQUID FUEL ROCKET out of PIPES, then testing it INSIDE with a bunch of stored props laying all around it :D They set themselves on fire so we don't have to.

poppy
December 21, 2005, 03:38 PM
Those guys and gals on MythBusters are pretty good. I watch them all the time especially when they start playing with firearms.

I'm confident that they will try several bullet weights and velocities and will be pretty scientific about it. I'll wait to see what their results are, but I still will not shoot a gun up in the air, except for a shotgun. poppy

HankB
December 21, 2005, 03:41 PM
. . . every july 4th and new years lots of bangers would fire their guns into the air, and usually people would get hit by the bullets returning to ground, wounding and killing them.Odds are these were not fired straight up, but at some angle.

There's going to be a vast difference in terminal effect between something fired straight up and something fired at, say, 45 degrees.

Carl N. Brown
December 21, 2005, 03:45 PM
For a .22 CB Long cap 740 fps with a 30 grain bullet gives me
about 36 ft/lbs kinetic energy.

A 150 grain .30 cal falling at 300 fps gives 30 ft/lbs kinetic energy.

It is NOT enough to be counted on being lethal for the military,
but I do not want to be under it any more that I would want to
take a hit from a .22 CB Long!

Mad Chemist
December 21, 2005, 03:54 PM
Whether or not the shots are fired straight up or to any angle relative to zenith will make a significant difference in energy retained upon impact.

If the round is fired straight up(90deg), most of the initial KE is lost. Some kinetic E is converted to potential energy as the object momentarily "floats" at it's apex.
This leftover energy is bled rapidly during decent from friction.

A round fired at any angle < or >(but not equal to)90deg will have greater energy upon impact than a round fired at approx. 90deg.

Physics isn't my strong suit, but this basic idea is correct. IIRC the equation to quantify it isn't very complicated.

Would any engineers on the board like to take a shot at this.
Sorry, bad pun.

JH

Czar
December 21, 2005, 03:59 PM
terminal velocity is a function of shape. A bullet that is more aerodynamic will have a higher terminal velocity. Imagine a skydiver tucked in a ball vs. spread eagle. They fall faster tucked in a ball since it's less cross sectional area into the airstream, and the shape is more round that flat (2 reasons to fall faster) Same applies to bullets.

Without conducting any experiments or running any math, lets assume 2 bullets, .45 and 9mm. I bet in this case both would have similar terminal velocities (if they tumble, then FMJ/HP doesn't matter and their aerodynamics are both bad) They fall at the same speed, the .45 will have more energy than the 9mm by exactly the same proportion as it outweighs the 9mm. In this case, I'd rather have a 9mm fall on me.

neither are going to cause a wound as they would at point blank to 100yards, but let the mythbusters explain away all those killed by bullets returning to earth after celebratory gunfire both here and abroad.

MrTuffPaws
December 21, 2005, 03:59 PM
.....however I would bet that a bullet would have a higher terminal velocity than a penny due to its hevier weight and its better ballistic coeficient. then you just compare the terminal velocity of the round with the normal velocity


Weight has nothing to do with terminal velocity because all things fall at the same rate due to gravity, if you ignore air resistance. TV does have to do with shape and cross sectional area though. Pennies are not very aerodynamic so they rotate while falling and they increase their drag. Bullets on the other hand would fall backwards (stability) and have only a cross sectional area that would affect drag. They would have a much higher TV.

Mass does have effect when it comes to hitting things. More mass, more energy. Either way though, I don't want anything going 200mph to hit me.

Carl N. Brown
December 21, 2005, 04:00 PM
Yes, a bullet fired *straight* up STOPS, zero velocity, then starts
falling, subject to wind resistence.
A bullet fired at an angle of 45 degrees or less will retain enough velocity
to be serious "plunging fire."

ScorpioVI
December 21, 2005, 04:02 PM
I grew up in the Southern Philippines (Davao City). By way of celebrating Christmas or New Years it's generally tradition to fire off your firearms into the air at midnight. As a consequence about a dozen people get killed every year from bullets falling out of the sky. One New Year's our house actually took 3 hits from two different calibers.

palerider1
December 21, 2005, 04:29 PM
thats just idiotic to fire your gun straight up into the air.

trapperjohn
December 21, 2005, 04:33 PM
Weight has nothing to do with terminal velocity because all things fall at the same rate due to gravity, if you ignore air resistance


you can not ignore air resistance and talk about terminal velocity. Without air resistance (drag) there is no terminal velocity and a falling object will continue to accelerate untill it hits something. Terminal velocity occurs when the object is falling fast enough that the force of gravity pulling down is the same as the drag force resisting the downward motion.
now the clinker is that all things being equal a larger body will have a higher terminal velocity. A 10 lb steel sphere will have a higher terminal velocity than a 5 lb steel sphere. thats because as you double the diameter you increase the air resistance by a factor of four, but you increase the weight and therefore the gravitational force by a factor of 8.
With that in mind a 50 caliber bullet is going to have a much larger terminal velocity than a 22 caliber or even a 30 caliber

Carl N. Brown
December 21, 2005, 05:22 PM
Right, surface area is a square of diameter: volume and weight is a cube.

Wind resistence is a squared value; weight is a cubed value.

Bone strength is a square of diameter, while weight is a cube: King Kong
at 25 feet is three times the size of a big gorilla: his bones are 3 x 3 = 9
times stronger, but his weight is 3 x 3 x 3 or 27 times heavier, which is
why he has such a pained expression in most of the movie.

Drifted totally off subject. Where was I?

Mot45acp
December 21, 2005, 05:31 PM
Would it disable a [B]ZOMBIEEEE[B]:eek:

BigFatKen
December 21, 2005, 05:34 PM
The world will rotate under you and you will be several feet west of where the bullet will fall. Then there is an effect (like Corliolis) that causes the bullet to move depending on the hemisphere also. it is used in long range artillery placement.

I'm still not going to try it. Most of the people who reported deaths were from lower angle shots.

slopemeno
December 21, 2005, 05:40 PM
You guys might google around for some of the "suicide by sub 12 ft/lb air rifle" articles I read recently. Seems about 3 or so people each year in the UK end their lives with non FAC air rifles (i.e sub 12 ft/lb). Interesting that something that 'low powered' can do the job. I dont want anything as hard as a bullet hitting me at 300 fps. Paintballs were bad enough....

AJ Dual
December 21, 2005, 07:04 PM
You guys might google around for some of the "suicide by sub 12 ft/lb air rifle" articles I read recently. Seems about 3 or so people each year in the UK end their lives with non FAC air rifles (i.e sub 12 ft/lb). Interesting that something that 'low powered' can do the job. I dont want anything as hard as a bullet hitting me at 300 fps. Paintballs were bad enough....


Yes, but...

Presumably all of them were point-blank contact shots to the head through the thin part of the temple, or possibly into the heart via the sternum. A bit different than dropping at 300fps onto the top of the cranium. Also, do these suicides take into account air embolisim, or secondary tissue disruption from the blast of air following the pellet?

I DO believe that a +/- 300fps terminal velocity bullet dropped with <60ft/lbs of K.E. CAN kill. But I'm firmly in the camp that it can't do it reliably. I agree that most, but not all, of the "falling" bullet deaths are at angles significantly less than 90° where horizontal velocity is adding significant fps and ft/lbs and giving the bullet a point-first orientation.

TexasRifleman
December 21, 2005, 08:00 PM
"Bullets Fired Straight Up" like "arrows fired straight up" leave their point of launch from a specific point on a rotating mass... It is impossible for them to return to that point, simply due to the fact that the mass is moving, 36,000mph... Said another way, the safest place to be after a bullet or arrow is fired "straight up" is exactly under point of launch. Wind, weight of bullet, velocity, and a whole host of other factors will also affect bullet or arrow after launch.

"Thou shalt not add thy velocity to the velocity of an object leaving thy hand."

If you are rotating around the earths axis at 26,000 mph, so is the bullet.

If what you state was true, then if I stood in the front of a 747 going 500mph, and I jumped up, I should smack the back wall of the fuselage.

Ain't gonna happen.

Shalako
December 21, 2005, 08:21 PM
Not only is the relative velocity of the bullet travelling normal to your point on the earth's surface, the atmosphere is also moving in rotation around the earth's axis. The velocity of the atmosphere though is not constant across its thickness and its decrease is nonlinear due to the variation in densities and viscosities of the different strata.

If this was a test question, I'd pick c.)

IndianaDean
December 21, 2005, 08:42 PM
What we need is for a whole big group of Al Quaida and Taliban guys to stand out in the open, fire their guns in the air and let the bullets come back down to test the theory.

Jim K
December 21, 2005, 09:09 PM
Let me see. First, a "bullet fired into the air" is not the same as a "bullet fired straight up". A shot fired with the barrel at an upward angle, which is almost any aimed shot fired at a target at any significant distance, is "fired into the air." At other than a 90 degree angle, it will retain at least some of its initial (muzzle) velocity when it comes down.

A shot fired straight up will stop in the air, losing all its initial velocity, and start to fall, just as if it were dropped from that height. Its velocity cannot exceed terminal velocity, which is about 300fps. This could be dangerous, but for an ordinary rifle bullet, not normally lethal.

The Coriolis effect has nothing to do with the earth turning under a bullet, and that does not happen. A bullet fired straight up and having nothing acting on it but gravity, will come down at the point where it was fired. (Of course, this just doesn't happen in the real world; a true 90 degrees is not easily attainable, and there are too many factors influencing any bullet fired through the air any time.)

Jim

AJ Dual
December 21, 2005, 09:34 PM
If you are rotating around the earths axis at 26,000 mph, so is the bullet.

If what you state was true, then if I stood in the front of a 747 going 500mph, and I jumped up, I should smack the back wall of the fuselage.

Ain't gonna happen.

The Coriolis effect has nothing to do with the earth turning under a bullet, and that does not happen. A bullet fired straight up and having nothing acting on it but gravity, will come down at the point where it was fired. (Of course, this just doesn't happen in the real world; a true 90 degrees is not easily attainable, and there are too many factors influencing any bullet fired through the air any time.)


Actualy...

It does. :) Although in the realm of arrows and centerfire ammunition the effect is negligable to the point of immeasurability. And it does not apply to a straight up shot... So it does not come into play in this debate. (Phew)

However, when the Germans were using the massive Krups rail-carriage "Paris Gun" in WWI, and the lesser known "V3" (Hitler's Vengance 3) booster cannon to try and shell England from across the channel, the Earth's rotation had to be taken into account when plotting the firing solutions to obtain accurate fire.

http://en.wikipedia.org/wiki/Coriolis_effect

The Coriolis Effect is also what makes Hurricaines spin. The Earth's rotational velocity is less at higher latitudes where the circle being traced over 24 hrs. is shorter in length than one traced by a point on the equator. If we can all agree that Velocity=Distance/Time and the Earth spins once in 24 hours, than the longer circle that the Equator traces has to be moving faster than any other latitude. Essentialy, the southeren half of the hurricaine is being swung around faster than the northeren half, and that makes it want to spin.

And it is indeed true. Because of the faster movment at the Equator, you actualy way about a pound less than you would at the poles! The centrifugal force (Actually, technicaly "conservation of angular momentum") at the Equator actualy cancels out gravity just a tad more than it does anywhere else.

So when plotting long range ballistic solutions the Earth's spin does have to be taken into account, or you won't hit what your aiming at. So it's moot for this discussion, but it is a real factor in ballistics.

Crosshair
December 21, 2005, 10:14 PM
*Note to self: Wear Hard Hat.*

bogie
December 21, 2005, 10:19 PM
"Bullets Fired Straight Up" like "arrows fired straight up" leave their point of launch from a specific point on a rotating mass... It is impossible for them to return to that point, simply due to the fact that the mass is moving, 36,000mph... Said another way, the safest place to be after a bullet or arrow is fired "straight up" is exactly under point of launch. Wind, weight of bullet, velocity, and a whole host of other factors will also affect bullet or arrow after launch.

Er... Sometimes those gusts of wind can blow a bullet _into_ the group.

cz75bdneos22
December 21, 2005, 10:38 PM
Obviously you don't know, but are willing to believe the mythbusters...YMMV i hope you never find out for yourself...i like to learn from the mistakes of other's first, before making my own...he,he!:p

gino
December 21, 2005, 10:47 PM
The terminal velocity of a bullet is not going to be very great. In my younger and dumber years, i spent a good bit of time in freefall. I'd be willing to bet money that an ordinary 9mm, 45acp, or 308 bullet would fall slower than a skydiver (120 mph). Don't ask me how I know this, lets just say that I jumped over farmland and sometimes other things fell out of the plane with me. ;)

If the bullet continues its gyroscopic spin during its entire flight, the bullet would stay pointed upwards and land base first, presenting a smaller aspect ratio to the wind, making it fall faster. If it stopped its gyroscopic spinning during freefall, it would start to tumble and this would slow it down some pretty significant amount.

You mean we don't have any active skydivers here who would be willing to let go of a bullet in freefal to see if it would stay falling with them? (Believe it or not, this could be done very safely.)

AZ Jeff
December 21, 2005, 11:48 PM
As the original poster mentioned in his opening post, Maj. Julian Hatcher did experiments on bullets fired vertically. His tests, performed in Miami and Daytona, Fla., in 1919-1920, were done firing .30/06 service bullets out of a Browning machine gun that had very carefully aligned on a tripod so as to have a true bore axis of 90 degrees to the horizon.

Hatcher's experiments showed the 150 grain flat based ball bullet of the day came down BASE FIRST, and would dent a pine board to the depth of about 1/16 inch. Calculations showed this bullet was returning to earth at about 300 fps. (Bullets return to earth base first because the center of gravity for most bullets is further to the base of the bullet than is the center of drag.)

For the 718 grain .50 BMG bullet of the day, terminal velocity was measured at about 500 fps.

Based on this, we can conclude that lighter and/or slower bullets than the two examples above might likely be very less-than-lethal if fired truely straight up.

(All of this can be found in the book "Hatcher's Notebook" starting on about page 505, for those of you interested in reading more.)

The reason that bullets fired on New Year's Eve (and the common Middle Eastern "bullets of joy") can cause more damage and death than that shown above is because RARELY are bullets TRULY fired directly vertically, and almost always have a significant horizontal velocity component, even when fired basically skyward. This horizontal component results in the equivalent of what machine gunners call "plunging fire", and is quite lethal.

The affects of the Coriolis acceleration, winds aloft, and other similar factors have little effect on bullets fired skyward when one considers that, in almost all cases, the shooter firing bullets "straight up" is really doing so without any real attempt to place the bore truly perpendicular to the ground. That lack of precision overshadows all other small scale considerations.

bogie
December 21, 2005, 11:59 PM
I remember seeing some WWII era small finned lead projectiles (about the size of a .45ACP round) in a Lancaster county museum about 30 years ago (sigh...). The story was that they were designed to mess up either troops or roofs when dropped en masse from bombers... I don't think I'd want to be standing in the open.

Taurus 66
December 22, 2005, 12:22 AM
A falling bullet could kill, it may not kill. There are a lot of variables. Here are just a few:


The bullet weight and mass, angle of descent ...


Did the bullet strike on it's nose?


Does the bullet achieve terminal velocity before impact?


Were there any crosswinds, up drafts, or sudden down drafts?


Was the victim standing still at time of impact, walking, running ...?


Is the victim male or female, a child or adult?


Is the injury blunt trauma or invasive?


Was the impact invasive to the point of affecting organs and/or major blood vessels?

VARifleman
December 22, 2005, 12:24 AM
Weight has nothing to do with terminal velocity because all things fall at the same rate due to gravity, if you ignore air resistance. TV does have to do with shape and cross sectional area though. Pennies are not very aerodynamic so they rotate while falling and they increase their drag. Bullets on the other hand would fall backwards (stability) and have only a cross sectional area that would affect drag. They would have a much higher TV.

Mass does have effect when it comes to hitting things. More mass, more energy. Either way though, I don't want anything going 200mph to hit me.
BS on everything has the same terminal velocity :cuss: :cuss: :cuss: .

Drop a penny and a coffee strainer next to eachother. they have different terminal velocities.

Just to make sure you understand this and don't mess other bits of gravity up...

Terminal Velocities are different for different objects depending on their size, weight, and shape.
Gravitational force is different for different objects. Gravitational Force is weight and we all know that our weights are different.

The acceleration due to gravity is the same for all objects. That's because F=ma, and when Fgrav=Fair resistance, that means that the net force on a free falling object is zero, thus acceleration is 0. This is why the terminal velocities differ on different shapes and weights, the shape decreases or increases the ballistic coefficient, and the weight is the gravitational force.

MrTuffPaws
December 22, 2005, 12:27 AM
you can not ignore air resistance and talk about terminal velocity. Without air resistance (drag) there is no terminal velocity and a falling object will continue to accelerate untill it hits something. Terminal velocity occurs when the object is falling fast enough that the force of gravity pulling down is the same as the drag force resisting the downward motion.


Thanks, I was trying to show that weight had little to do with TV.

MrTuffPaws
December 22, 2005, 12:29 AM
BS on everything has the same terminal velocity :cuss: :cuss: :cuss: .

Drop a penny and a coffee strainer next to eachother. they have different terminal velocities.

Just to make sure you understand this and don't mess other bits of gravity up...

Terminal Velocities are different for different objects depending on their size, weight, and shape.
Gravitational force is different for different objects. Gravitational Force is weight and we all know that our weights are different.

The acceleration due to gravity is the same for all objects. That's because F=ma, and when Fgrav=Fair resistance, that means that the net force on a free falling object is zero, thus acceleration is 0. This is why the terminal velocities differ on different shapes and weights, the shape decreases or increases the ballistic coefficient, and the weight is the gravitational force.


Again, if you read my post, I say if you ignore air resistance, and TV has nothing to do with weigth or mass, but shape and size.

VARifleman
December 22, 2005, 12:34 AM
you can not ignore air resistance and talk about terminal velocity. Without air resistance (drag) there is no terminal velocity and a falling object will continue to accelerate untill it hits something. Terminal velocity occurs when the object is falling fast enough that the force of gravity pulling down is the same as the drag force resisting the downward motion.
now the clinker is that all things being equal a larger body will have a higher terminal velocity. A 10 lb steel sphere will have a higher terminal velocity than a 5 lb steel sphere. thats because as you double the diameter you increase the air resistance by a factor of four, but you increase the weight and therefore the gravitational force by a factor of 8.
With that in mind a 50 caliber bullet is going to have a much larger terminal velocity than a 22 caliber or even a 30 caliber
UGH!!!!

10/5=2...

volume goes up by two, that means that the radius has changed by a factor of 2^(1/3) which means that surface area has changed by a factor of 2^(2/9) which is less than two. This is why it has a higher terminal velocity. :banghead: :banghead:

You all are going to give me a stroke if you keep talking this nonsense.

VARifleman
December 22, 2005, 12:38 AM
Again, if you read my post, I say if you ignore air resistance, and TV has nothing to do with weigth or mass, but shape and size.
As pointed out THERE IS NO TERMINAL VELOCITY WITHOUT AIR RESISTANCE!! Air resistance is the only thing limiting speed as you fall. Otherwise, you'd acelerate until you hit somthing. Since some of what affects air resistance is shape and size, you are complete contradicting yourself.

VARifleman
December 22, 2005, 12:40 AM
Thanks, I was trying to show that weight had little to do with TV.
Air resistance, the only thing that affects TV, increases by a factor of velocity^3, with larger weights and fairly good profiles, it does not change it dramatically, but with smaller weights and bad profiles, it changes it considerably.

SkyDaver
December 22, 2005, 12:49 AM
Weight has nothing to do with terminal velocity because all things fall at the same rate due to gravity, if you ignore air resistance. TV does have to do with shape and cross sectional area though. Pennies are not very aerodynamic so they rotate while falling and they increase their drag. Bullets on the other hand would fall backwards (stability) and have only a cross sectional area that would affect drag. They would have a much higher TV.

Mass does have effect when it comes to hitting things. More mass, more energy. Either way though, I don't want anything going 200mph to hit me.

MrTuffPaws, I was an active skydiver for over 16 years, and have nearly 500 freefalls.

Weight has a GREAT deal to do with terminal velocity. You are correct that objects fall at the same rate in a vacumn, but in the air, or other medium, weight is a major factor.

Over my skydiving experience, my weight varied from about 165 to 200 lbs.

At 165, in a polycotton suit, I struggled to fall as fast as most other jumpers. At 185 in that same suit, I had no problems. At 200lbs, I was setting the fall rate (other jumpers were trying to keep up with me) My shape and cross sectional area were close to constant.

At 200 lbs, in a smooth nylon suit, I fell like a greased anvil.

You can prove that weight matters yourself. Go buy some table tennis balls. Make a small hole in one, and fill it with liquid (Elmer's glue might be good, since it would set after a bit.)

Drop both of them from outstretched arms. The filled one will hit the ground first.

JohnKSa
December 22, 2005, 12:56 AM
I'd be willing to bet money that an ordinary 9mm, 45acp, or 308 bullet would fall slower than a skydiver (120 mph). Don't ask me how I know this, lets just say that I jumped over farmland and sometimes other things fell out of the plane with me.As you note in the rest of the post, if the bullet continues to spin (and it will, based on Hatcher's tests) it will fall much faster since a tumbling object is far less aerodynamic.

Falling bullets can certainly be lethal, a bit of internet search will turn up fatalities, I did some research a couple of years back around New Years and came up with a large number of respectable news sources reporting fatalities from falling bullets.

The speculation about HOW lethal they are is pretty crazy, IMO. After all, you have an 80% chance of surviving an AIMED shot from a handgun in a violent encounter. I'd say that it's less likely you'd die from getting hit by a falling bullet, but it can and DOES happen.

Hatcher's numbers (energy threshold for fatal wounds) are misleading. It is possible to be killed by a projectile having far less energy than he states. The one or two airgun fatalities each year prove it.

Bottom line. Falling bullets can be fatal--no speculation or mythbusting necessary, you can easily find well documented instances.

Firethorn
December 22, 2005, 02:52 AM
*Note to self: Wear Hard Hat.*

Just what I was thinking. From what I've read, a bullet of decent size can indeed kill when falling at terminal velocity if it gets a lucky hit.

However, the amount of additional protection needed is construction hard hat level, not kevlar military helmet level.

armyranger
December 22, 2005, 05:26 AM
A bullet or any object reachs "terminal velocity" when it reachs its max speed, with is 33 feet per sec. Nothing will fall faster than 33 ft per sec unless some other force was used i.e. throwing it down, ect. So no, it will not kill you, ( ever been to south america or mexico, they shoot hand guns in the air to celebrate all sorts of events)

KB180
December 22, 2005, 05:37 AM
Whether it kills you or not, common sense tells me that I wouldn't want to be standing where the projectile eventually falls to earth (whether it's a bullet or bowling ball). :D

cz75bdneos22
December 22, 2005, 05:44 AM
A bullet or any object reachs "terminal velocity" when it reachs its max speed, with is 33 feet per sec. Nothing will fall faster than 33 ft per sec unless some other force was used i.e. throwing it down, ect. So no, it will not kill you, ( ever been to south america or mexico, they shoot hand guns in the air to celebrate all sorts of events)

i have been/lived in the above mentioned...for my 35 years...i don't know what you are talkin about...you have not seen a death by causation...fair, but to say otherwise is not fair either...i will show you pictures at the turn of the New Year if the moderators will allow...in those countries that you mention by the way, they take a different approach when it comes to freedom of the press..

Firethorn
December 22, 2005, 06:04 AM
A bullet or any object reachs "terminal velocity" when it reachs its max speed, with is 33 feet per sec. Nothing will fall faster than 33 ft per sec unless some other force was used i.e. throwing it down, ect. So no, it will not kill you, ( ever been to south america or mexico, they shoot hand guns in the air to celebrate all sorts of events)

Whoa... You need to go back to school, Armyranger.

I don't know where you got '33 feet per second' from, but I'm guessing you got it from gravity, of which the acceleration is '32 feet per second per second' for earth. With no atmosphere, that means that after falling for 1 second, you're traveling at 32 ft/s. Ater two, you're up to 64 ft/s.

Terminal velocity depends on atmospheric effects. Basically, it's the point at which the object's wind resistance equals the acceleration by gravity, so you're no longer speeding up. TV can change rapidly and drastically depending on the mass, size and shape of an object.

This is how parachutes work. By increasing surface area, increasing drag, you lower a human's terminal velocity down to something not so terminal. :D

Now, you take a solid chunk of lead such as a bullet and it's TV is going to be fairly high. It's reasonably aereodynamic and dense, do it takes a high speed for air resistance to stop it's accelleration. A piece of paper is almost the opposite. The bigger the bullet, the faster it'll be at TV.

M67
December 22, 2005, 06:35 AM
So we're talking about a slow moving projectile hitting blunt end first.

Isn't that exactly how the .45 acp is supposed to work?

:D

trapperjohn
December 22, 2005, 07:24 AM
volume goes up by two, that means that the radius has changed by a factor of 2^(1/3) which means that surface area has changed by a factor of 2^(2/9) which is less than two. This is why it has a higher terminal velocity.

You all are going to give me a stroke if you keep talking this nonsense.

as a professor of engineering who teaches this very subject i resent your insult and would point out that you have a few errors in your assumption.

drag on an object is based on cross sectional area not surface area. for anything circular the cross sectional area is pi r squared. most elemtary school children know this. therefore if you double the radius you increase mass by a factor of 4

now the volume if a sphere is 4/3 pi r cubed. if you double the radius you increase the volume (mass) by a factor of 8

why is it so hard for you to see that?

EZ CZ75
December 22, 2005, 07:38 AM
I believe that Sectional Density is what is missing in this conversation. A ton of feathers and a ton of bricks both have the same mass/weight, but massively different sectional densities. This has a great effect on terminal velocity.

HankB
December 22, 2005, 08:34 AM
I don't want to get hit by a 150 grain projectile falling at 300 ft/sec. This carries about 30 ft.lbs of kinetic energy.

An Aguila Colibri .22 Short fires a 20-grain bullet at a claimed 500 ft/sec. It's very quiet when fired from a rifle, since it uses the priming only, no powder. This has a "mere" 11 ft.lbs of energy. It will down a small deer if put in the right spot.

So will one of the more powerful spring-piston .177 air rifles.

(No, I don't recommend hunting anything except small pests with .22 Colibris or air rifles, I'm just making the point that it doesn't take a whole lot of energy to be potentially deadly.)

Need I say it's a really, really bad idea to shoot randomly into the air if the bullet may hit someone when it comes down?

RioShooter
December 22, 2005, 08:34 AM
All of this academic debate is entertaining, but a few anecdotal incidents might be instructive.

On the 4th of July a young girl was standing in her backyard talking on the phone, when her father saw her drop to the ground.

A bullet shot into the air by a nearby celebrant had struck her on the top her head. She died on the spot.

So much for theory!

Templar223
December 22, 2005, 09:45 AM
Completely wrong. I know a man from pakistan that lost 3 sons all of which died from bullets hitting them in the top of the head going straing down.

-Dev

I'm glad I'm not his son. Sounds like the guy has some seriously bad karma.

I'm guessing most fatalities of this sort or from a parabolic arc of sorts / indirect fire as opposed to "straight up / straight down".

I lived on a lake growing up and like a good little industrious kid :neener: experimenting with his 10-22, I fired "straight up" and watched the bullets impact into the lake... while standing under the corner of the house...

How I lived through my pre-teen and teen years, I don't know.:evil:

I never had a bow & arrow or I probably would have done the same with those.

John

mfree
December 22, 2005, 11:02 AM
Uh, drag is determined, and pardon me for being vague because this is from memory, by a function of the cross section, the coefficient or drag, air viscosity, and the reynolds number (iirc another derivative dealing with laminar flow seperation).

For subsonic speeds a bullet falling base first has *less* drag than one falling point first. Pointy noses are for supersonic use, round noses work best below that, ever see an airliner?

The spin of a bullet will lend it a gyroscopic effect that will keep the axis of spin pointed in the same direction, barring precession effects (wobble). That's why the base falls first, because it was pointed down when it left the barrel.

Terminal velocity will increase at 32ft/s/s until air drag is equivalent to the force of gravity on the bullet.

Lightweight bullets may never develop the terminal velocity required to do anything other than sting really bad. Heavier bullets and those with a greater ballistic coefficient might. If stuck just right, they may kill... the very top of the skull would be vulnerable to a point impact like that since there's very little "padding" to take the shock away from the bone.

280PLUS
December 22, 2005, 11:56 AM
I'd say bullet weight would be the greatest factor. For example, if you shot a 29 gr projectile straight up and managed to hit yourself on the noodle when it comes down, it probably wouldn't do much damage. Now you take a 72 POUND projectile, shoot it straight up and then hit yourself on the head with it on it's return to earth you may have a bit of a problem. So it's really all relative.

Incidentally, I happen to know Trenton, NJ is another place that rains a lot of lead right about at midnight on New Years Eve. :eek:

trapperjohn
December 22, 2005, 12:20 PM
external flow over a body-drag

calculation of terminal velocity

terminal velocity occurs when the downward force on the object due to gravity equals the upward force on the body due to drag

downward force=mass of object * acceleration due to gravity (mg)

upward force =.5 * air denisty* coefficient of drag* cross sectional area * velocity squared (1/2*rho*Cd*Ac*v^2)

drag coefficient is dependant on air density, air viscosity, projectile size, projectile shape, and projectile velocity

for subsonic regions, drag coefficient is dependant on reynolds number which is a function of air denisty, air viscosity, velocity, projectile diameter
Re=velocity*viscosity*diameter/density
coefficient of drag for a particular chape would be looked up at the appropriate reynolds number from a chart or table

for super sonic velocities, crag coefficient is a function of Mach number, the drag coefficient would be looked up for a particular shape would be looked up at the appropriate mach number

normal projectiles in our atmosphere will be in the subsonic region

Carl N. Brown
December 22, 2005, 02:41 PM
A 150 grain bullet starting at apex of a 90 degree trajectory
will start at zero, accelerate at 32.16 feet per second per second
until air resistence keeps it from going faster than 300 or so ft/sec.
300 * 300 + 150 / 32.16 / 7000 / 2
That's abouit 30 ft/lbs kinetic energy. That can seriously hurt, especially
a child whose skull is still growing and not as hard as some of ours here.

The military may not consider 30 ft/lbs a reliable mankiller, but it will kill.
A .25 ACP is what? 80 ft/lbs?

SkyDaver
December 22, 2005, 03:01 PM
A bullet or any object reachs "terminal velocity" when it reachs its max speed, with is 33 feet per sec. Nothing will fall faster than 33 ft per sec unless some other force was used i.e. throwing it down, ect.

Nothing will fall faster than its terminal velocity, without other force, but the terminal velocity is NOT 33 fps for all objects.

A two mile freefall, in stable box position, lasts approximately 70 seconds. That's on the order of 150 ft/sec.

Head down skydivers, or style skydivers (they do their freefall in a tuck) go even faster.

33 fps? That's only 22.5 mph.

Brad Johnson
December 22, 2005, 04:39 PM
To summarize...

1. Regardless of how fast the projectile is going up, it will come down at a specific speed (Terminal Velocity) which is variable depending on weight and aerodynamic drag.

2. Given the time of flight for most common rifles in a verticle shot scenario, the projectile will still be spinning sufficiently fast to stabilize it in flight until it impacts the ground. Thus, it will probably land base-first.

3. The energy imparted by most common rifle bullets in the above situation is relatively modest, even as compared to some small rifle and pistol catridges. However, an impact to a vulnerable area such as the top of the human cranium can render sufficient trauma to be lethal. Lethal trauma can range from actual penetration of the cranial bones to something as innocuous as a non-penetrating impact sufficient to cause a subdural bleeding or swelling, both of which can kill.

Now HERE's the real kicker question. Should be good for some interesting discussion....

If a gun is held perfectly horizontal as it is fired, and if the bullet is not inturrupted in flight and eventually impacts the ground, will the axis of rotation of the projectile when it hits the ground remain the same as the rifle bore axis, or will the axis of rotation follow the ballistic trajectory?

In other words, will the bullet hit the ground parallel to the bore of the rifle, or will it tilt a little during its ballistic arc?

:neener: *stands back and waits for the show...* :neener:

:evil:

Brad

mfree
December 22, 2005, 05:10 PM
The bullet will hit the ground parallel to the axis of the bore.

VARifleman
December 22, 2005, 05:11 PM
you can not ignore air resistance and talk about terminal velocity. Without air resistance (drag) there is no terminal velocity and a falling object will continue to accelerate untill it hits something. Terminal velocity occurs when the object is falling fast enough that the force of gravity pulling down is the same as the drag force resisting the downward motion.
now the clinker is that all things being equal a larger body will have a higher terminal velocity. A 10 lb steel sphere will have a higher terminal velocity than a 5 lb steel sphere. thats because as you double the diameter you increase the air resistance by a factor of four, but you increase the weight and therefore the gravitational force by a factor of 8.
With that in mind a 50 caliber bullet is going to have a much larger terminal velocity than a 22 caliber or even a 30 caliber


UGH!!!!

10/5=2...

volume goes up by two, that means that the radius has changed by a factor of 2^(1/3) which means that surface area has changed by a factor of 2^(2/9) which is less than two. This is why it has a higher terminal velocity.

You all are going to give me a stroke if you keep talking this nonsense.



as a professor of engineering who teaches this very subject i resent your insult and would point out that you have a few errors in your assumption.

drag on an object is based on cross sectional area not surface area. for anything circular the cross sectional area is pi r squared. most elemtary school children know this. therefore if you double the radius you increase mass by a factor of 4

now the volume if a sphere is 4/3 pi r cubed. if you double the radius you increase the volume (mass) by a factor of 8

why is it so hard for you to see that?

Actually…I have no errors there, and I’ll prove it for you. First, look at your quote, it’s above. We’re talking about a sphere, a 10 lb and 5 lb sphere as you stated in your original post. Since the density is the same as it’s the same material, and as you stated in your last post, attempting to put me down as you professors never like it when you’re shown up by a student (sophomore in Civil Engineering), volume would go up by 8 if you doubled the radius. Thus, weight would go up by eight, not two like you originally stated. So…now for some math…

Weight (W)= density(rho)*volume(V)
V=4/3*Pi*r^3
2*W[1]=W[2]
W[1]=rho*4/3*Pi*r[1]^3
For ease: kappa= 4/3*rho*Pi
Thus: W[1]=kappa*r[1]^3

W[2]=kappa*r[2]^3
W[2]=2*W[1]=2*kappa*r[1]^3= kappa*r[2]^3

So…

2*r[1]^3=r[2]^3
r[2]=(2*r[1]^3)^(1/3)
r[2]=2^(1/3)*r[1]

Thus…an increase in radius by a factor of 2^(1/3), like I said in my post.

Now…the cross sectional area, as you corrected, I misspoke there, but since both surface area and cross sectional area of a sphere both only have the term r^2 in there, it doesn’t affect the numbers to use either formula.

A[1]=2*Pi*r[1]^2
A[2]=2*Pi*r[2]^2
A[2]=2*Pi*(2^(1/3)*r[1])^2
A[2]=2*Pi*2^(2/3)*r[1]^2

So: A[2]=2^(2/3)A[1]

Alright…so I messed up in squaring the area term and came up with 2^(2/9) instead of 2^(2/3) due to a mistake in squaring said term, not a fundamental error, my bad. You however, made quite a few blatant errors. Thanks for playing…:neener:

280PLUS
December 22, 2005, 05:13 PM
The bullet will hit the ground parallel to the axis of the bore. +1

JohnKSa
December 22, 2005, 05:39 PM
The bullet will hit the ground parallel to the axis of the bore.Only in a vacuum.

Red Dragon
December 22, 2005, 05:54 PM
see this post

http://www.thehighroad.org/showthread.php?t=151075

g56
December 22, 2005, 05:56 PM
Not that it matters, the odds of someone being able to point a gun in the precise position to allow the bullet to fall in the same spot are virtually nil.
That's the real deal, falling bullets from people shooting up in the air are in a very high trajectory, when they come down they can definitely kill, one fired absolutely straight up, which is highly unlikely, if it stabilized point down it could be very dangerous, if it's tumbling, probably not. A coin dropped from altitude tumbles, thus increasing air resistance tremendously, to the point that it probably wouldn't be very dangerous.

cz75bdneos22
December 22, 2005, 06:01 PM
Only in a vacuum.
+ 1
there will be certain external factors affecting the bullets path...thus, it won't arrive as it came out the barrel-parallel. wind, gravity, dust particles, foreingn matter in air path, etc. :rolleyes:
like when your'e driving a car and let go of the steering wheel...alignment, road surface condition, wind, etc, will afect trajectory of car's resting place when it comesto a stop..:scrutiny:

CAPTAIN MIKE
December 22, 2005, 06:13 PM
I would like to personally THANK those members of the Iraqi national defense forces who, during the initial hours of Desert Storm's first aerial assault on Bagdhad, went outside and shot straight up into the sky --- trying to shoot down missiles launched from submarines, surface warfare ships and Navy & Air Force aircraft flying overhead.

These brave and stupid soldiers contributed significantly to the overall success of The Mission that night. They did so well, their actions were specifically called out by the Pentagon's official News Guy who briefed the press after the opening salvos of Desert Storm were launched.

Yes, shooting straight up into the sky and thinking it's a "good idea" is not what you or I should consider to be either prudent or Tactically Wise."

trapperjohn
December 22, 2005, 06:21 PM
Varirifleman, you need to read things a little more carefully,. I was not teaching an engineering course here, I was attempting to communicate some basic principles to people without a background in aerodynamics.

I made the statement by way of example that a 10 lb sphere would have a faster terminal velocity than a 5 lb sphere. note at the end of that statement was a period. Periods typically mean the end of a sentance. I then went on to state it is because if you double the diameter you quadruple the drag force, but increase the mass by a factor of 8. I could have gotten a bit more technical and stated " this is becase drag force is a squared function of diameter and wieght is a cubic function of diameter" but because we have an audience of varied educational levels I left it in the original statement

Nowhere did a say that we doubled the diameter to get from 5lbs to 10 lbs, you made that assumption on your own.

you must be like most of my students when they study. They try work the problems but do not read the text :neener: :neener:

Taurus 66
December 22, 2005, 10:49 PM
A ton of feathers and a ton of bricks both have the same mass/weight, but massively different sectional densities. This has a great effect on terminal velocity.

A ton of this and a ton of that may not have the same mass. Weight and mass are different. A ton of cotton verses a ton of gold: The gold will have a greater mass because mass is the molecular density of an element, though both will weigh the same.

Read some of these:

http://www.lapdonline.org/bldg_safer_comms/holiday_safety_tips/new_years_gunfire.htm

http://www.straightdope.com/classics/a950414b.html

http://goaskgrandpa.com/sample13.htm

Lone_Gunman
December 22, 2005, 10:56 PM
One New Year's our house actually took 3 hits from two different calibers.


This statement proves the point that bullets were not fired straight up, unless someone was standing on top of the house when the shot was fired.

Third_Rail
December 22, 2005, 11:05 PM
Lone_Gunman, what about the earth's rotation? :neener:

VARifleman
December 22, 2005, 11:22 PM
A ton of this and a ton of that may not have the same mass. Weight and mass are different. A ton of cotton verses a ton of gold: The gold will have a greater mass because mass is the molecular density of an element, though both will weigh the same.
Um...no.

F=ma, remember?

F[g]=W=m*g (g=acceleration due to gravity)

same weight, under the same circumstances (hieght from the earth, measuring system, etc), will yeild the same mass, even though the molecular mass is different.

trapperjohn
December 22, 2005, 11:44 PM
A ton of this and a ton of that may not have the same mass. Weight and mass are different. A ton of cotton verses a ton of gold: The gold will have a greater mass because mass is the molecular density of an element, though both will weigh the same.

Yes, mass and weight are different, but you dont quite understand how the two relate.

mass is defined by an objects resistance to change in motion. an object with a higher mass will be harder to accelerate than an object with less mass, hence we get the famous f=ma.

that being said, weight is defined as the force due to graviatational pull on an object of given mass. it does not depend on the material.

something that has 1lb mass will exert 1 lb force when acted on by gravity at sea level.

now if you take that same one lb mass, wether it be feathers or lead, or depleted uranium and place it on the moon, it will have the same 1 lb mass as on earth, but a much lower weight as the gravitational pull is greatly reduced.

Taurus 66
December 22, 2005, 11:52 PM
Um...no.

F=ma, remember?

Yes, this is Force = mass x acceleration. Where in this formula is there a mention of something about two objects weighing the same having the same mass? This is just a calculation for the force applied.

F[g]=W=m*g (g=acceleration due to gravity)

same weight, under the same circumstances (hieght from the earth, measuring system, etc), will yeild the same mass, even though the molecular mass is different

F[g]=Wm x g perhaps? Again, F = something here. No mention of M = something. Where and how does acceleration alter the mass of any object? Please feel free to further elaborate.

JohnKSa
December 23, 2005, 12:55 AM
what about the earth's rotation?What about wind? Has anyone figured out how far a bullet can travel sideways before landing if shot up at an 89 degree angle instead of 90 degrees? Are we really saying that 1 degree off vertical (which could result in the bullet coming down many yards from the point of origin) isn't straight up enough to be straight up?

Taurus 66
December 23, 2005, 02:36 AM
Yes, mass and weight are different, but you dont quite understand how the two relate.

mass is defined by an objects resistance to change in motion. an object with a higher mass will be harder to accelerate than an object with less mass, hence we get the famous f=ma.

that being said, weight is defined as the force due to graviatational pull on an object of given mass. it does not depend on the material.

something that has 1lb mass will exert 1 lb force when acted on by gravity at sea level.

now if you take that same one lb mass, wether it be feathers or lead, or depleted uranium and place it on the moon, it will have the same 1 lb mass as on earth, but a much lower weight as the gravitational pull is greatly reduced.

I was referring to the amount of matter in an object, or the cubic density of an element given for any volume of space, and not by the definition the measure of an object's resistance to acceleration, or yotta ...

http://www.visionlearning.com/library/pop_glossary_term.php?oid=

Please scroll down to "Mass".

Matt G
December 23, 2005, 04:11 AM
armyranger said:
A bullet or any object reachs "terminal velocity" when it reachs its max speed, with is 33 feet per sec. Nothing will fall faster than 33 ft per sec unless some other force was used i.e. throwing it down, ect. So no, it will not kill you, ( ever been to south america or mexico, they shoot hand guns in the air to celebrate all sorts of events)
Incorrect.

Falling objects accelerate at g, which is gravity constant, or 32.16 feet per second per second, or g = 980.665 centimeters per second squared, all assuming that you are at 45&#176; latitude at sea level.

They will continue to accelerate at that rate until the rate of acceleration is offset by the air resistance. This is a function of frontal surface area against mass. In other words, density and shape are very important to a falling object's terminal velocity.

The average terminal velocity of a skydiver is 55 fps to 75 fps, a good deal faster than your reported maximum speed of 33fps. (BTW, 33 fps is a mere 22.5 miles per hour)

The higher above sea level you get, the more rarified the atmosphere becomes, giving a higher terminal velocity.

I would have thought all this was common knowledge to a "ranger sniper." :)

trapperjohn
December 23, 2005, 05:37 AM
I was referring to the amount of matter in an object, or the cubic density of an element given for any volume of space, and not by the definition the measure of an object's resistance to acceleration, or yotta ...

I checked your link. it states the following:

Mass a fundamental property of matter which is a numerical measure of the inertia of an object or the amount of matter that an object contains. The mass of an object is different from its weight as mass is independent of the gravitational field exerted on an object.



nowhere in there does it make any reference to any "Cubic density" nor any mention of volume. it is a fact that a ton of anything has the same mass as any ton of any other thing. their denisty and therefore volumes may be different. but their masses will be the same.

inertia of on object is that objects RESISTANCE TO CHANGE IN MOTION, This confirms what I stated earlier

Art Eatman
December 23, 2005, 09:28 AM
Hey, you guys are supposed to remember all this high school physics. You're closer to those years than I am. I gotta dredge up stuff from over fifty years back!

Sticking with the English system, the good old force of gravity (or, the Earth's suction) is 32.16 feet per second, per second. So, at the end of the first second that bullet is falling 16.08 fit/sec. Minus the retardation created by friction with the air. At the end of the secondd second, you're up to 48 ft/sec, minus air friction. And so it goes, until the friction from the air equals the force of gravity. (I may not have phrased this exactly correctly, but it's close enough for Internet babbble.)

In the English system of measurement, Mass is (or used to be) denoted in "poundals", which is merely the weight in pounds divided by 32.16. And that tells you that weight and force are the same, since Force = Mass times Acceleration, or from Algebra, Mass = Force divided by Acceleration. Gotta be consistent with the units of measurement, right?

In the "I ain't sure, but..." department, I read somewhere, way long ago, that the maximum free-fall speed of an irregularly-shaped (non-streamlined) body, the terminal velocity in air is around 220 mph. I haven't done the Google thing for "terminal velocity". That's left as an exercise for the student. :)

I'd expect a vertically-fired bullet to fall back base first, since its rotation would exert the usual gyroscopic effect. I'd expect a boat-tail to fall faster that a flat-base. If the 220mph idea has any merit whatsoever, that's 11/3 times 88 ft/sec, or about 323 ft/sec.

I'm running out of conclusions and coffee, so I'm off to that more important thing: Coffee.

:), Art

"Gravity is a myth. The earth sucks."

SkyDaver
December 23, 2005, 10:56 AM
The average terminal velocity of a skydiver is 55 fps to 75 fps, a good deal faster than your reported maximum speed of 33fps. (BTW, 33 fps is a mere 22.5 miles per hour)


Minor correction, Matt. If you average in the terminal velocity while under an open canopy, perhaps the average terminal velocity is in the 55-75 fps, but in stable 'box man' freefall, it's running about 160 fps (110 mph or so). Back in the day of big floppy suits, it may have been slower, but probably not much less than 100 mph. Formation skydivers empirically discovered it was easier to control their flight in a tighter suit, falling faster.

Free fly skydivers (flying stable, but anything but belly to earth) are falling a bit faster.


The higher above sea level you get, the more rarified the atmosphere becomes, giving a higher terminal velocity.


That's true, noting however that most skydiving is done below 15,000 ft MSL, and the difference is negligible. As you descend, you'll continue to slow as the air gets thicker. Generally speaking, most jump runs are at speeds above the jumpers terminal velocity anyway, so the jumpers actually start slowing down immediately upon exit. It's just the vector that changes. Good jumpers can do a couple of formations before their velocity vector gets to vertical (while they're still 'on the hill')

Taurus 66
December 23, 2005, 11:02 AM
I checked your link. it states the following:



nowhere in there does it make any reference to any "Cubic density" nor any mention of volume. it is a fact that a ton of anything has the same mass as any ton of any other thing. their denisty and therefore volumes may be different. but their masses will be the same.

inertia of on object is that objects RESISTANCE TO CHANGE IN MOTION, This confirms what I stated earlier

The mass of an object is different from its weight as mass is independent of the gravitational field exerted on an object.

I repeat:

The mass of an object is different from its weight as mass is independent of the gravitational field exerted on an object.

The mass of an object is different from its weight. Hmmm ... What do you suppose this means? :rolleyes:

Stick to trapping buddy :D

Matt G
December 23, 2005, 11:52 AM
Minor correction, Matt. If you average in the terminal velocity while under an open canopy, perhaps the average terminal velocity is in the 55-75 fps, but in stable 'box man' freefall, it's running about 160 fps (110 mph or so). Of course you're right-- I had forgotten the average terminal velocity of a person, so I looked it up, not paying any attention to the fact of course that was the speed of a man under canopy. :o

There's some interesting reading (http://hypertextbook.com/facts/JianHuang.shtml) about a fellow (US Air Force Captain Joseph Kittinger) who, back in 1960, jumped from a He balloon gondola from the highest altitude to date-- 102,800'-- and gained the highest terminal velocity ever obtained before or (to my knowledge) since. Because the atmosphere up there is about 1.5% of the density of the atmosphere at sea level, he fell a LOT longer before obtaining terminal velocity. They figured it to be about 612 mph. He got over 12,000 feet to accelerate!

But the rules change a tad at that height-- even the constant of constants-- g-- is 9.72 m/s^2!

Medusa
December 23, 2005, 12:52 PM
You guys have overlooked one thing on it, at great densities it d&#245;esn't matter much, but at low ones definitely will.

Besides, Newton defined the formula as a=F/m, as acceleration is created by the summary force and is dependant on the mass.

What is drastically different with bricks and feathers? If they have same physical mass then they have drastically different volume. And what force is dependant of the volume? Since every object pushes out the substance it's in, air in this example, it is affected by Archimedes force, F=Rho(Air)*Volume*g and is created by the fact that pushed out substance wants to push back in and thus trying to lift the body (you all feel lighter in water, like), total force that affects the object is the difference of 2 forces, weight and Arch-s, F = m*g - Rho*V*g = (m - Rho*V)*g. If these 2 forces are equal, the body floats, if weight is larger, then sinks and if weight is smaller, the body "takes off". Why do you think the airships fly? Since bullet has a very small volume the Arch-s force is marginal, but with feathers it's very major one. Besides, in metrology the lift by air must be taken into account when weighting something (taking the volume of weights and object into account) and wanting the result with several numbers after comma.

Mass is a physical "thing", as any body is made of atoms (eventually), in every atom there's protons, neutrons and electrons, each one have distinct physical mass, so the total mass of the body is a sum of the masses of all basic particles.

And if to blow the things more complicated, the mass IS relative, as it is dependant of the speed :
Lorentz factor Gamma = 1/(1-v^2/c^2)^0.5 , where v is the speed of the body and c is the speed of light. Note that the speed is relative - depends on the background.
m = Gamma * m0 ; m0 is the real physical mass, m is the mass that the body has due the movement. Yes, plane that flies with speed of 1080 km/h (300 m/s) has a 1.0000000000005 times bigger mass than a standing one. IF the plane weights, say, 50 tons (50 000 kg) then the increase of mass is 2.5e-5 g ie 25 micrograms. This doesn't seem much, but with very high speeds (comparable to the speed of light) this is very noticeable (if the speed is 1/10 c, then the increase in mass is 1%)

Weight is simply a force, actually a projection of summarum force on the axis that connects the centres of masses of both the body and Earth (for example), that is applied to the body by the mass of the Earth (or any other object in space) (dent in the spacetime continum) and the Arch-s force is also a player here. And yes, the gravity is between any 2 bodies, even on Earth (like between the ship and boat), just the force has so small magnitude that this is rarely noticed.
Fgrav = G * m1 * m2 / r^2

BTW a question to the public, how big is the gravitational acceleration at the center of Earth? Infinite or not?
EDITED: some details and added some more

Mongo the Mutterer
December 23, 2005, 01:02 PM
Completely wrong. I know a man from pakistan that lost 3 sons all of which died from bullets hitting them in the top of the head going straing down.

-DevUh OK. I'll bite ... I have to hear how THIS happened...

MrTuffPaws
December 23, 2005, 01:06 PM
MrTuffPaws, I was an active skydiver for over 16 years, and have nearly 500 freefalls.

Weight has a GREAT deal to do with terminal velocity. You are correct that objects fall at the same rate in a vacumn, but in the air, or other medium, weight is a major factor.

Over my skydiving experience, my weight varied from about 165 to 200 lbs.

At 165, in a polycotton suit, I struggled to fall as fast as most other jumpers. At 185 in that same suit, I had no problems. At 200lbs, I was setting the fall rate (other jumpers were trying to keep up with me) My shape and cross sectional area were close to constant.

At 200 lbs, in a smooth nylon suit, I fell like a greased anvil.

You can prove that weight matters yourself. Go buy some table tennis balls. Make a small hole in one, and fill it with liquid (Elmer's glue might be good, since it would set after a bit.)

Drop both of them from outstretched arms. The filled one will hit the ground first.

Thinking about this again, and you are correct. Weight does have an effect on TV. Sorry for the confusion.

Herself
December 23, 2005, 01:15 PM
I repeat:
The mass of an object is different from its weight. Hmmm ... What do you suppose this means? :rolleyes:

Stick to trapping buddy :D

It means, Taurus, that mass is a measurement of inertia, while weight is that mass in a specified gravitational field.
So, while weight and mass are not the same, any two objects of the same mass in the same gravitational field will weigh the same. They might not weigh the same when weighed, say, on Kwajaleen as when weighed in your back yard or at a factory in Brazil, but if they have the same mass as one another and we weigh them both on the same set of scales at different but not too far apart times and in the same geographical area [was: in the same place at the same time], we will find them to be the same weight

Got it?

--Herself

(Space cadet since before men landed on the Moon)
____________________________________
Edited to remove geekbait, with apologies for not having been more clear. And I'm attracted to geeks -- I married one! -- so please don't take offense.

Taurus 66
December 23, 2005, 01:33 PM
Hershelf, just what are you trying to say?

but if they have the same mass as one another and we weigh them both in the same place at the same time, we will find them to be the same weight


Two objects cannot occupy the same space at the same time.

Space cadet, please return to earth ... err better yet .....

benEzra
December 23, 2005, 01:40 PM
mass is defined by an objects resistance to change in motion. an object with a higher mass will be harder to accelerate than an object with less mass, hence we get the famous f=ma.

that being said, weight is defined as the force due to graviatational pull on an object of given mass. it does not depend on the material.

something that has 1lb mass will exert 1 lb force when acted on by gravity at sea level.

now if you take that same one lb mass, wether it be feathers or lead, or depleted uranium and place it on the moon, it will have the same 1 lb mass as on earth, but a much lower weight as the gravitational pull is greatly reduced.
You're all wrong. In general relativity, mass is the invariant length of a particle's momentum four-vector. :D :D :D

BTW, the U.S. pound is a measure of mass, not weight (it is legally defined as a certain fraction of a kilogram). However, the weight of a mass of 1 U.S. pound at one standard gravity is quite commonly used as a measure of force, as is the kilogram-force in many metric countries (though newtons are used more in scientific work).

Two objects cannot occupy the same space at the same time.
She's saying in the same general location. Two objects that weigh the same as each other when weighed on the same tabletop in Denver, will still weigh the same as each other when weighed on the same tabletop in Death Valley. However, both objects will be slightly heavier in Death Valley due to being a little closer to the earth's center. (Ignoring buoyancy effects here...)

saltydog452
December 23, 2005, 01:49 PM
Art does have a wonderful way of expressing himself. Must be 'cause he lives so close to the Study Butte Store. Which reminds me of a quotation that someone painted onto the south wall of The Study Butte Store. It reads like this.."This is the place where brilliant minds assemble to willfully pool ignorance with questionable logic in order to reach absurd conclusions" attribited to B. Franklin.

salty.

Herself
December 23, 2005, 01:53 PM
SkyDaver wrote:
"You can prove that weight matters yourself. Go buy some table tennis balls. Make a small hole in one, and fill it with liquid (Elmer's glue might be good, since it would set after a bit.)

"Drop both of them from outstretched arms. The filled one will hit the ground first."

So Galileo and generations of physicists, physics students and an Apollo astronaut were wrong, then, and the acceleration due to gravity is not a constant? All of them either misinterpeted their observations or just plain lied? (And tennis balls have zero drag in air?)

I think not. I saw live video of the guy dropping a heavy object (a hammer, wasnt it?) and a feather on the Moon, and they both hit at the same time. It was on TV. You could get it on tape or DVD and time it down to the nearest 1/30th of a second.

"Force" (How Hard It Hits) is not "Speed" (How Fast It Is Going) nor is it "Mass" (How Much Interia It Has, also known as How Difficult It Is To Change Its Motion). It's the product of both. C'mon, we surely all know that from the great Caliber Debates, with speedy, light 9mm rounds argued against slow but massive .45s!
The acceleration due to 1 gravity is a constant, whatever it is, 9.8m/sec/sec? But "Force" does not equal "acceleration" in the case of a dropped object: it is not thrown, no external force is imparted other than the same force that is keeping me in my chair right now (no, not "eunni!").

Weight doesn't affect speed when you drop things. Shape can matter unless you're in a vacuum and height sure does, but not weight -- at least, weight does not matter until it hits you, and then matters not only because of "how fast," but "how much intertia." If it has a lot of intertia, it takes a lot of energy to change its motion. In the case of something being dropped on you or shot at you, that change of motion would be stopping it. The energy is passed along to you. Ouch!

...Galieo was grumpy on this subject, too. It seems so intuitive that the speed of a dropped object would be affected by its weight! But it is incorrect. Here's a good explaination: The Big Misconception (http://www.glenbrook.k12.il.us/gbssci/phys/Class/1DKin/U1L5e.html)

Look here for a nice tutorial: Physics Of Dropped Stuff (http://www.glenbrook.k12.il.us/gbssci/phys/Class/1DKin/U1L5b.html) That's http://www.glenbrook.k12.il.us/gbssci/phys/Class/1DKin/U1L5b.html if I did the link improperly.

How does this affect a bullet shot straight up? As near as I can tell, when it comes back to ground it should act just like one dropped from the highest point it reached: same speed, and, if they're the same caliber and type of bullets, the same mass.
Can it kill you? Only if it would when dropped from the same height it reached when shot vertically. I'd avoid trying this with .50 cal BMG rounds.

--Herself

(I can too work a slide rule, I'd just rather let the boys do it 'cos it makes them feel all rugged and In Charge).

Taurus 66
December 23, 2005, 03:54 PM
If I fired a 50 BMG round straight down from way up high in the atmosphere, how long would it take to decelerate to 9.8 m/s? Do you have a formula handy? Sorry for changing the topic slightly, but the main topic is pretty much shot. Some say, "Yes a bullet will kill." Others say the opposite.

Strange concept though: Drop an object from 30,000 feet, it will accelerate. Point the barrel down and shoot, the bullet instantly begins to decelerate.

Firethorn
December 23, 2005, 04:23 PM
If I fired a 50 BMG round straight down from way up high in the atmosphere, how long would it take to decelerate to 9.8 m/s?

Simple answer: It won't. Terminal velocity for a .50BMG round is faster than 9.8 m/s.

Your choice of 9.8 m/s is interesting. You seem to be confusing speed and acceleration.

9.8 m/s is a velocity
9.8 m/s^2 is an acceleration, specifically that of earth's gravity at sea level.

Do you have a formula handy? Sorry for changing the topic slightly, but the main topic is pretty much shot. Some say, "Yes a bullet will kill." Others say the opposite.

Well, it's a difficult equation. Think about the variation in lethality for shots for all the various calibers from .22LR to .50BMG. Different weights for the bullets, different shapes, etc.

It all depends on how aereodynamic the bullet is and cross-sectional density.

The heavier the bullet, the more volume and mass for the cross section and the faster it'll end up going.

That's all without figuring out what kind of a hit it takes to kill a human. Like what's been said, a child with a still unfused skill is far more vulnerable than a rock headed adult. Even then, you still have the equivalent of golden BB's.

a .22LR bullet at TV might only be enough to give somebody a headache. A .50BMG round has a good chance of killing if it hits the skull.

Most common round fired into the air is probably the .30 caliber 7.62x39 round, followed by various pistol calibers, which it's doubtful will even reach TV on the way down.

Strange concept though: Drop an object from 30,000 feet, it will accelerate. Point the barrel down and shoot, the bullet instantly begins to decelerate.

I don't find it strange, but then I've always thought differently.

Variations in velocity depend upon all factors impacting on the object, in this case a bullet. The two major ones are gravity and air resistance.

The acceleration from gravity is more or less a constant. The decelerative force of air resistance goes up the faster the speed, and the moment you go supersonic things change drastically. As some point these two forces negate each other. This is termed 'terminal velocity'.

A bullet shot straight down is faster than TV, so it slows, as the air resistance is greater than gravity. A bullet dropped is slower than TV, the air resistance is less than gravity, so it accelerates.

Taurus 66
December 23, 2005, 04:55 PM
9.8 m/s^2 is an acceleration,

Are you saying "9.8 m/s² is an acceleration,"? I just want to make certain ^2 is a commonly shared scientific "squared" symbol for use in the forums.

Firethorn
December 23, 2005, 05:11 PM
Are you saying "9.8 m/s² is an acceleration,"? I just want to make certain ^2 is a commonly shared scientific "squared" symbol for use in the forums.

Yes, It's a pain in the butt to get the superscript version.

9.8 meters per second per second.

Herself
December 23, 2005, 05:31 PM
Taurus, please look at the link I posted. It explains that an object dropped in the 1g field we know and enjoy will gain speed or accelerate at a rate of about 9.8 meters per second for every second that elapses.

At t (for time) = 0S (for seconds), V (velocity) = 0 m/S (meters per second)
At t = 1S, V = 9.8 m/S
At t = 2S, V = 19.6 m/S
At t = 3S, V = 29.4 m/S
At t = 5S, V = 49.0 m/S
At t = 10S, V = 98.0 m/S
And so on.

How fast it ends up going when it hits the surface of the body that is attracting it depends on how high it was when it was dropped. (We are assuming the only motion the two have with respect to one another is the straight downward fall).

If the fall is through some medium, like air or water or gearbox oil, then drag ("air resistance," if it's just falling through the atmosphere) or even bouyancy become issues. In the example of a lead bullet in air, this is not insignificant and suggests that the bullet might even reach some "terminal velocity" where the air is doing such a good job supporting it that it cannot fall any faster. A parachute is a real-world example of this; once your chute opens, your rate of fall is no longer increasing (and an "increase in rate of motion" is an acceleration), or at least increases at a much slower rate than happens in a free fall, and you descend at a constant or nearly constant speed.


As for your "bullet fired straight down," it might speed up or slow down after it leaves the muzzle; that depends on how close the muzzle velocity is to the terminal velocity and if the acceleration due to gravity can make up the difference in the medium through which it is moving and available travel distance.

...I am really doubtful that anything shoots rounds unstreamlined enough and fast enough to make them slow down when fired straight down, but that's uninformed intuition; having not done the math and not being an aeronautical engineer, I could very easily be wrong

There are a lot of variables in that story problem and because wind resistance is such a big part of it, I can't give you an answer.

If we go to the moon and build a tall tower, then lean out the top and shoot down, the bullet will speed up all the way down, increasing velocity at a rate about one-sixth it would in 1 gravity. It might be an interesting shooting sport, once there are ranges on the moon.

--Herself

"Ground Control to Capt. Morgan..."
"No, that's Major Tom!"
"You...hic!...pick your ossifers, I'll pick mine!"

Art Eatman
December 23, 2005, 06:09 PM
I allus heard about infinity/monkeys/typewriters/Shakespeare's works. Fer some reason I wuz reminded...

:), Art

trapperjohn
December 23, 2005, 11:09 PM
tell you what taurus, go get 1 lb mass of chicken feathers, and 1 lb mass of lead and then measure the weight of both and get back with us.

I assure you the weight will be the same.

if the wieghts are are different you can rewrite all the physics books.

Taurus 66
December 24, 2005, 12:00 AM
tell you what taurus, go get 1 lb mass of chicken feathers, and 1 lb mass of lead and then measure the weight of both and get back with us.

I assure you the weight will be the same.

if the wieghts are are different you can rewrite all the physics books.

#1. Since it's Christmas, I'll bet you the house 1 lb mass of chicken feathers, a 1 lb mass of lead, don't weigh the same as Sunday mass. :neener:

#2. Where the heck am I going to get chicken feathers at this hour?? The back room of a Popeyes restaurant? :p

#3. I could rewrite all physics books if ... ? Why? The current confusion is enough entertainment.

Upsidey sidey down and a initty initty out!

Up is down and left is right, fast is slow and black is white,
Red is blue and big is small, winter's summer, spring is fall,
Top is bottom, crooked's straight, the number one is really eight,
Hard is soft like sweet is sour, a century is just one hour.

MERRY CHRISTMAS EVERYONE!!! NOT HAPPY HOLIDAYS!!!

I hope you all get what you've been wanting, especially all you bright scientists. :p

EZ CZ75
December 24, 2005, 12:32 AM
I just had to put in one more word that I find it funny how much time we all just put into a moot point on the internet.:neener:

Isn't techonology grand!

SkyDaver
December 24, 2005, 02:39 PM
SkyDaver wrote:
"You can prove that weight matters yourself. Go buy some table tennis balls. Make a small hole in one, and fill it with liquid (Elmer's glue might be good, since it would set after a bit.)

"Drop both of them from outstretched arms. The filled one will hit the ground first."

So Galileo and generations of physicists, physics students and an Apollo astronaut were wrong, then, and the acceleration due to gravity is not a constant? All of them either misinterpeted their observations or just plain lied? (And tennis balls have zero drag in air?)

I think not. I saw live video of the guy dropping a heavy object (a hammer, wasnt it?) and a feather on the Moon, and they both hit at the same time. It was on TV. You could get it on tape or DVD and time it down to the nearest 1/30th of a second.


Sigh. Remember air resistance? Two ping pong balls, one unaltered, one filled with glue. They will have exactly the same drag coefficient, but because one is heavier, its terminal velocity will be greater because we are not on the moon! It's certainly possible that the height of out stretched arms may not be enough for a standard ping pong ball to reach terminal velocity, in which case both balls might hit nearly at the same time, but I think that it will be a perceptible difference (might have to try it out this weekend)

If it is not, then dropping those two objects from a second story window almost certainly will show a difference.

Of course, I only have about seven hours of freefall, so what do I know about air resistance.

Firethorn
December 24, 2005, 03:38 PM
...I am really doubtful that anything shoots rounds unstreamlined enough and fast enough to make them slow down when fired straight down, but that's uninformed intuition; having not done the math and not being an aeronautical engineer, I could very easily be wrong

There are a lot of variables in that story problem and because wind resistance is such a big part of it, I can't give you an answer.

One thing to remember is that he was talking about a .50BMG, which is most definitly supersonic.

found a calculator at http://exploration.grc.nasa.gov/education/rocket/termvr.html

Plugging in the numbers, it gives a terminal velocity of a 750 grain .50BMG at 215.5 feet/second. Assuming a drag coefficient of .2(quite a streamlined bullet).

Speed of sound is 1,116 feet/second. So, yes, the bullet will start slowing the moment it leaves the barrel, despite being pointed straight down.

I'm sure that 215.5 ft/s is enough to kill, especially given the huge bullet size.

Gunpacker
December 24, 2005, 03:40 PM
Uhh, isn't the formula for mass:
Mass=weight/acceleration of gravity??
conversely:
Weight=mass times acceleration of gravity
No allowance for wind resistance there, and no change for size of object.
Mass of 1 lb object is same no matter what the material or where it is moving, IMO.
It would take the same force to stop or deflect a lb of feathers or a lb of lead while in motion.
Obviously wind resistance exerts a greater force on a large body than on a small body, thus the small body will fall faster in air.
In a vacuum, it doesn't matter, the acceleration of gravity is the same on all bodies, and all will fall at the same speed. Some will hit the ground with greater force if the mass is greater.

Matt G
December 24, 2005, 05:17 PM
Herself said:
So Galileo and generations of physicists, physics students and an Apollo astronaut were wrong, then, and the acceleration due to gravity is not a constant? All of them either misinterpeted their observations or just plain lied? (And tennis balls have zero drag in air?)

I think not. I saw live video of the guy dropping a heavy object (a hammer, wasnt it?) and a feather on the Moon, and they both hit at the same time. It was on TV. You could get it on tape or DVD and time it down to the nearest 1/30th of a second.

SkyDiver did not say "tennis balls"-- he said "table tennis balls." Most folk call these "ping pong balls." Unweighted ping pong balls will reach terminal velocity from shoulder height. They will NOT reach TV from shoulder height if filled with water-- they will continue to accelerate all the way into the ground.

Ol` Joe
December 24, 2005, 06:04 PM
According to the NRA Firearms Fact Book (published 1964) the army did testing on bullets in free fall and determined the drag factor of the bullet (BC) is the factor that determins the speed of a falling bullet. The only force acting on a bullet fired straight up @ 90 degree is gravity. It will gain speed until drag force equals the pull of gravity, at which point the bullet will stop gaining velocity. They calculate a 30-06 fireing a 180 gr PSP bullet will reach a altitude of 10120 ft. The max velocity of the bullet in fall will then depend on its attitude as it drops. A bullet can fall base first, turn over and fall point first, or tumble. They calculated the terminal velocity would be 180 fps for one tumbling, 323fps base first and 457 fps for a bullet fallng point first

Herself
December 24, 2005, 06:18 PM
Sigh. Remember air resistance? Two ping pong balls, one unaltered, one filled with glue. They will have exactly the same drag coefficient, but because one is heavier, its terminal velocity will be greater because we are not on the moon! It's certainly possible that the height of out stretched arms may not be enough for a standard ping pong ball to reach terminal velocity, [...], but I think that it will be a perceptible difference [...].

If it is not, then dropping those two objects from a second story window almost certainly will show a difference.
Fine, SkyDaver, but you're quibbling. You wrote:
"You can prove that weight matters yourself. Go buy some table tennis balls. Make a small hole in one, and fill it with liquid (Elmer's glue might be good, since it would set after a bit.)

"Drop both of them from outstretched arms. The filled one will hit the ground first."
You didn't write "drag." You wrote "weight." Perhaps you wrote in haste?
With respect to the acceleration due to gravity of a dropped object, weight does not matter.

Of course, I only have about seven hours of freefall, so what do I know about air resistance.
I have none, unless one counts the few seconds at a time doing silly things with a light airplane. It is possible to understand the physics underlying a thing without experienceing it, just as it is possible to experience a thing without understanding it.

But it looks like you and I are on the same page in the end.

--Herself

JohnKSa
December 24, 2005, 06:45 PM
They calculate a 30-06 fireing a 180 gr PSP bullet will reach a altitude of 10120 ft. That means that the round trip will be about 4 miles (2 up and 2 down). My back of the envelope WAG says that the time of travel will be around 40 seconds. Remember, it's moving quite slowly on the way down. Anybody got the wind drift numbers for a 30-06 bullet during a 40 second flight? EVEN if the bullet is fired EXACTLY straight up, a light wind will move that bullet a LONG way while it makes a 4 mile round trip.

Handgun bullets won't go that high, but we're still talking about a round trip that far exceeds a mile and time of travel that gets up around half a minute. Wind drift is going to be tremendous. Clearly the fact that a bullet lands a long way from where it is shot is NOT sufficient evidence to prove that it wasn't shot straight up.

VARifleman
December 24, 2005, 06:46 PM
Yes, this is Force = mass x acceleration. Where in this formula is there a mention of something about two objects weighing the same having the same mass? This is just a calculation for the force applied.



F[g]=Wm x g perhaps? Again, F = something here. No mention of M = something. Where and how does acceleration alter the mass of any object? Please feel free to further elaborate.
F=ma. force=W when a=acceleration due to gravity. They will weigh the same when in the same area. Note that I said that their weight will be the same, not that there weight = their mass. Units here... F (N)= m(kg) * a(m/s^2)

F[g]=Wmg? What in the heck do you think this is? Well...I'll let you know...it's just a jumble of letters put together by someone who is ignorant in physics. Afterall, I stated earlier that F[g]= W.
:banghead:

Time to go back to school for some of ya'll...

VARifleman
December 24, 2005, 06:53 PM
#1. Since it's Christmas, I'll bet you the house 1 lb mass of chicken feathers, a 1 lb mass of lead, don't weigh the same as Sunday mass. :neener:

#2. Where the heck am I going to get chicken feathers at this hour?? The back room of a Popeyes restaurant? :p

#3. I could rewrite all physics books if ... ? Why? The current confusion is enough entertainment.

Upsidey sidey down and a initty initty out!

Up is down and left is right, fast is slow and black is white,
Red is blue and big is small, winter's summer, spring is fall,
Top is bottom, crooked's straight, the number one is really eight,
Hard is soft like sweet is sour, a century is just one hour.

MERRY CHRISTMAS EVERYONE!!! NOT HAPPY HOLIDAYS!!!

I hope you all get what you've been wanting, especially all you bright scientists. :p
Get the amount of something with low density (like feathers) that equals 1 kg of mass, and then get its weight (in Newtons). The weight will be 9.8 N. Now get 1 kg of lead, steel, or some other metal. Weigh it as last time, it will be 9.8 N as well (As long as YOU didn't screw up any of the measurements).

VARifleman
December 24, 2005, 06:59 PM
The mass of an object is different from its weight. Hmmm ... What do you suppose this means? :rolleyes:

Stick to trapping buddy :D
It means exactly what we've been telling you. Mass is independant of gravity whereas weight is dependant on it. Two objects of the same mass in the same location will have the same weight. In the metric system, mass measured in kg, weight in Newtons will be 9.8 times greater than mass. That's because F=ma where a=g=9.8 m/s^2 For the english system, the pound is a weight, whereas the slug is a mass. The weight in lbs will be 32.17 times higher in value than its mass in slugs for the same reason, F=ma where a=g=32.17 ft/s^2.

I'd suggest against arguing physics with either of us. You won't win.

PaladinVC
December 24, 2005, 07:03 PM
I have seen a lot of gunnish discussion boards address a lot of mathematical notions, but there's nothing so entertaining as watching these things go down on THR. Times like this, it seems like the entire membership of this forum is made up of engineers.

Delightful.

On a side note, I'm from Erie, PA, and a little girl caught a falling handgun round in the head a few New Years ago. She was wounded, but survived. If I had fired a round into the air that night, I'd fell absolutely rotten thinking that it might have been mine that hit her. One more reason not to shoot guns into the sky.

trapperjohn
December 24, 2005, 09:42 PM
mass and weight can actually be a difficult concept for people to get their heads around when it is first contemplated.

mass is defined as an objects resistance to change in motion, or its resisitance to accelerating. a clear cut definition of mass was not really needed untill newton came up with the relationship F=ma showing that a more massive object is harder to accelerate. people are a little more used to thinking in terms of weight because we judge the "massiveness" of an object either by lifting it and noting the difficulty in overcoming the gravitational pull on it, or by using a scale such as a bathroom scale that really just measures force. sometimes people test their grip by squeezing a bathroom scale to see what kind of force they can generate, this shows that what is really being measured is a force, and a weight is a force.
one means of measuring mass is probably the oldest method of measuring weights called the balance scale. A beam is supported in the center and each end has a tray suspended from it. The object to be "weighed in the balance" is placed in one tray, known "weights" (which are realy masses) are placed in the other tray untill the beam is horizontal. Since the force of gravity is the same on each mass gravitational effects are cancelled out and the mass can be determined. This is a good illustration to show that it doesnt matter wither you are using lead or chicken feathers or lead or reindeer antlers. if one will recall the known masses used in these cases is usually lead or brass. someone measuring the weight, or mass of feathers would not demand that the known weights used to measure it also be feathers, they would be content to use any known weight regardless of its composition.
This attribute called mass is dependant only on the object and independant of its surroundings, including any forces acting on it such as gravity. Weight, on the other hand is the force exerted by a mass due to gravitational pull.
it can be noted that if 1 lb force is applied to 1 lb mass the acceleration can be measured to be 32.17 ft/s^2. the unit of mass that 1lb force will cause to accelearate at 1 ft/s^2 is called the "slug" numerically it is equivelant to 32.17 lb mass. a pound mass is defined as the amount of mass that will exert 1 lb force due to gravity at sea level. SI units are significantly eaiser to deal with where a 1 newton force will cause 1 kg mass to accelerate at 1 m/s^2.

Taurus 66
December 24, 2005, 09:56 PM
It means exactly what we've been telling you. Mass is independant of gravity whereas weight is dependant on it. Two objects of the same mass in the same location will have the same weight. In the metric system, mass measured in kg, weight in Newtons will be 9.8 times greater than mass. That's because F=ma where a=g=9.8 m/s^2 For the english system, the pound is a weight, whereas the slug is a mass. The weight in lbs will be 32.17 times higher in value than its mass in slugs for the same reason, F=ma where a=g=32.17 ft/s^2.

I'd suggest against arguing physics with either of us. You won't win.

It's not about winning for me. It's only about killing time. It's about victory for all you wonderful scientists here, but I bet you're more than just a trapper. You probably deliver firewood too. I need a face cord, or don't you protract that kinda mass along the curve? It's gonna get cold again after the big day tomorrow. :rolleyes:

PEACE

trapperjohn
December 24, 2005, 10:59 PM
It's not about winning for me. It's only about killing time. It's about victory for all you wonderful scientists here, but I bet you're more than just a trapper. You probably deliver firewood too. I need a face cord, or don't you protract that kinda mass along the curve? It's gonna get cold again after the big day tomorrow.


you wer quoting someone other than me.

you are correct, Trapperjohn is a nickname i picked up a long time ago when I actually did run a trapline. Unfortunately I havent done any in over 15 years.

my current occupation is as an engineering professor. Therefore I spend my days trying to pound sound principles into engineering students such as VAririfleman, and i used to teach physics as well to students that were not on an engineering tract. As an educator in real life my goal is not to win or lose, it is to educate.

Taurus 66
December 24, 2005, 11:19 PM
you wer quoting someone other than me.

What's the difference?! 5 in one, a half Canadian dozen in the other ...

trapperjohn
December 24, 2005, 11:25 PM
What's the difference?! 5 in one, a half Canadian dozen in the other ...

whats the difference? about the same as there is between mass and weight :neener:

JohnKSa
December 25, 2005, 12:17 AM
It's not about winning for me. It's only about killing time.JMO, but it OUGHT to be about informing, or exchanging information and learning. There's plenty of static on the web, and there are plenty of threads that are purely social. Why "kill time" cluttering up a thread that has a good chance of being a good source of information?

VARifleman
December 25, 2005, 12:52 AM
It's not about winning for me. It's only about killing time. It's about victory for all you wonderful scientists here, but I bet you're more than just a trapper. You probably deliver firewood too. I need a face cord, or don't you protract that kinda mass along the curve? It's gonna get cold again after the big day tomorrow. :rolleyes:

PEACE
Well, I'm the one you quoted, and I'm not a trapper (not trapperjohn afterall, I'm VARifleman). I'm a civil engineering student at NC State, as for "delivering firewood", that's not what I do. I am currently working for a boiler repair company near my hometown in Northern VA. You really don't make much sense at all in this thread, Taurus.

thorazine
December 25, 2005, 01:23 AM
I have seen a lot of gunnish discussion boards address a lot of mathematical notions, but there's nothing so entertaining as watching these things go down on THR. Times like this, it seems like the entire membership of this forum is made up of engineers.

lol indeed.

Topics like this make for an excellent and educational read.

Taurus 66
December 25, 2005, 01:28 AM
Well, I'm the one you quoted, and I'm not a trapper (not trapperjohn afterall, I'm VARifleman). I'm a civil engineering student at NC State, as for "delivering firewood", that's not what I do. I am currently working for a boiler repair company near my hometown in Northern VA. You really don't make much sense at all in this thread, Taurus.

and I'm not a trapper (not trapperjohn afterall, I'm VARifleman). I'm a civil engineering student blah blah, blah blah, yackety smack ...

WHAT'S DA DIFEERREEENNNNCCCCE?! Like there's some difference between a dime minted in Denver or in DC! Give me a break!!! I can toss a dozen of you geeks to the wind and get blown back at me 12 calculators, 11 slide rulers, 10 protractors, 9 sharpened pencils, 8 floppy disks, 7 paper cuts, 6 thick frame glasses, FIVE GOLDEN RULES, 4 physics books, 3 paper clips, 2 bogus degrees and a cartridge in a pear tree! :neener:

JohnKSa
December 25, 2005, 01:30 AM
WHAT'S DA DIFEERREEENNNNCCCCE?! Like there's some difference between a dime minted in Denver or in DC! Give me a break!!!There is only one thing worse than being witty--and that is NOT being witty. John Cleese, Monty Python.

Taurus 66
December 25, 2005, 01:55 AM
There is only one thing worse than being witty--and that is NOT being witty. John Cleese, Monty Python.

Well there's only one thing worse than being John Cleese, but THR won't allow me to stoop to that level - Jim's Python

Herself
December 25, 2005, 09:04 AM
...And thus this thread proceeds, in an appropriately seasonal spirit of mutual goodwill and chumship....

Right?

Bottom line: Don't point a gun at something you don't intend to destroy. Don't shoot a gun at anything you don't intend to destroy. That includes the sky!

I dont know about the rest of you, but without the sky, I'd sunburn really easily. So don't go tryin' to shoot it out!
;)

Also it's impolite to drop rounds in the neighbor's yards, even if they're only going fast enough to leave a mark.

--Herself

PS: Appropriately seasonal greetings to everybody.

Geno
December 25, 2005, 09:12 AM
It was a .50 cal fired straight up. And, as Chicken Little still lives on, it didn't kill him. Myth busted. :neener:

Doc2005

Medusa
December 25, 2005, 11:47 AM
Ok, I'll settle this once and for all.
Lets say we have 1000 kg heavy material as uranium with density of 19 050 kg/m^3 and 1000 kg of light material as cork with density of 340 kg/m^3.
As we are weighting these in air, the the density of air is 1.239 kg/m^3,
acceleration by gravity g = 9.80665 N/kg (m/s^2) (International standart).

So uranium has the volume of Vur = 1000 kg / 19 050 kg/m^3 = 0.05249343832 m^3;
Volume of cork Vcork = 1000 kg / 340 kg/m^3 = 2.94117647059 m^3

Both have weight by gravity of 9806.65000 N
Archimedes's force (law of buoyancy): F = Rho(air) * Volume * g
Uranium : F = 1.239 kg/m^3 * 9.80665 N/kg * 0.05249 m^3 = 0.63782 N
Cork : F = 1.239 kg/m^3 * 9.80665 N/kg * 2.94118 m^3 = 35.73659 N

So the uranium has REAL weight in air Wur = 9806.01218 N
cork has REAL weight in air Wcork = 9770.91341 N

So cork IS LIGHTER as we are weighting them in AIR (you cannot discard that). A ton of cork weights 0.358 % less than a ton of uranium.

take that:neener:

They didn't teach you in school that we are actually not in vacuum, but in air and it does have a weight thus also a uplifting effect? Why do you think the Zeppelins fly, by faith? You know, when the body has a very close density to air or even less the body can have NEGATIVE weight even if it's mass is measured in tons.

HERSELF, if to chew letters then the "thing" that prevents you from burning up is Earth's magnetic field and ozone layer. Without atmosphere the Earth would be as warm as any other plain rock in the space and have close to zero habitability (including the definite and felt lack of anything worth to breath).

EDITED: I have 2 formulas for calculating the weight of bodies:
W [N] = 9.80665 * mass [kg] - 12.15044 * Volume [m^3] or
W [N] = 9.80665 * mass [kg] * (1 - 1.239 / Densitybody [kg/m^3])

So, if mass is constant, the bigger volume/ lesser density the smaller weight.

SkyDaver
December 25, 2005, 01:00 PM
Fine, SkyDaver, but you're quibbling. You wrote:
"You can prove that weight matters yourself. Go buy some table tennis balls. Make a small hole in one, and fill it with liquid (Elmer's glue might be good, since it would set after a bit.)

"Drop both of them from outstretched arms. The filled one will hit the ground first."
You didn't write "drag." You wrote "weight." Perhaps you wrote in haste?
With respect to the acceleration due to gravity of a dropped object, weight does not matter.


I have none, unless one counts the few seconds at a time doing silly things with a light airplane. It is possible to understand the physics underlying a thing without experienceing it, just as it is possible to experience a thing without understanding it.

But it looks like you and I are on the same page in the end.

--Herself

I did write 'weight'. Both ping pong balls will have the same amount of drag, as they have the same shape and size. The filled one will have greater weight, and therefore will have a higher terminal velocity. I picked ping pong balls because I'm fairly certain that drag on an unaltered one will be discernable to the naked eye over a very short distance.

TV of an object depends upon the medium through which it is falling, the shape of the object, the size of the object, and the weight of the object.

Here's another experiment. Take two pieces of aluminum foil. Ball one up as tight as you can. Leave the other flat. Drop both. Observe which one hits the ground first.

Herself
December 25, 2005, 01:46 PM
HERSELF, if to chew letters then the "thing" that prevents you from burning up is Earth's magnetic field and ozone layer. Without atmosphere the Earth would be as warm as any other plain rock in the space and have close to zero habitability (including the definite and felt lack of anything worth to breath
What keeps me from dieing of sunburn from visible and UV light here on this deee-lightful ball of dirt (other than a thick layer of mud, animal fat, clothing, or some form of shelter between my fair hide and the the solar orb) would be, in fact, the atmosphere, which includes that layer of ozone you have mentioned. Not that it does such a great job of it, thus explaining the brisk sales of wide-brimmed hats, sunscreen and similar items, espcially in the summer months.

The Earth's magnetic field keeps me from being toasted by solar output of the energetic-particle or alpha. beta and gamma variety, especially when ol' Sol is really angry. And I approve wholeheartedly of it for that reason.

You've got some beef with the air or magnetism of this planet, maybe? It was good enough for Grandma and it is darned well good enough for you! ;)

--Herself

Herself
December 25, 2005, 02:05 PM
I did write 'weight'. Both ping pong balls will have the same amount of drag, as they have the same shape and size. The filled one will have greater weight, and therefore will have a higher terminal velocity. I picked ping pong balls because I'm fairly certain that drag on an unaltered one will be discernable to the naked eye over a very short distance.

I think it doubtful. It is easy to experimentally verify. I can arrange a wind-free drop of some 14' very easily, and perhaps a camera with a wide enough lens, etc. May take a couple of weeks to set up a proper backdrop with calibration marks and don't expect better than 30 frames per second.

TV of an object depends upon the medium through which it is falling, the shape of the object, the size of the object, and the weight of the object.
I have not disputed that in general, especially in re size and shape of the object. Weight? I do not think it is a hugely significant factor in air.

The way problems of this sort are generally approached is as a series of approximations, each refining the previous ones. The first-order approximation, the one that shows the most marked effects, is to ignore the air (really quite thin, especially compared to a lead slug) and plug in distance and gravtitational constant. Then one starts to refine the model as required for the specific application.
If the application is finding out if one ought to dodge a falling bullet, first-order numbers are good enough for me, and tell I most certainly should.

As for you skydiving through air, or the fat chap on one side of you and the skinny fellow on the other, you are all less dense than raindrops and a lot less streamlined. You've going to get results greatly affected by things other than first-order effects even if you never pop the canopy.

Here's another experiment. Take two pieces of aluminum foil. Ball one up as tight as you can. Leave the other flat. Drop both. Observe which one hits the ground first.
Tsk. Tsk, tsk. Flat piece of foil folds once when released, presents not so much more surface are than the balled-up piece, both hit the ground about the same time in the majority of times after successive trials. Aluminium foil is just not very stiff. Sometimes the flat one flutters, grabs air and hits later: that's not a free fall. And it's a much poorer approximation of the behavior of, oh, a .50BMG round than is the balled-up foil. And both pieces of foil weigh the same.

A 1-g field with a roughly 14.7 psi oxygen/nitrogen mix filling it is a really lousy place to do basic physics experiments. Small wonder Galileo was a grouch and Newton went pretty much mad!

--Herself

Medusa
December 25, 2005, 04:34 PM
Hey Herself, no beef here, but my thoughts: high energy UV and up ionizes the air (hence the calling - ionosphere) and thus looses energy, low energy UV has smaller probability to jump the band gap and actually ionize the air, thus the blue spectrum and low UV is plenty to cause sunburn. so no lousy job. You know, there's no such thing as bad weather, there's only impropriate outfit, ie use the sun lotion :neener:

Anyway, my point was that the working parts are important, hence all the hype about the ozone layer and it's imperfections, if to think to that, the main reason of climate warming (half-bluff as it is, because all the temp is usually balanced by the ice - it's melting takes away the exess heat, thus keeping the temp nicely balanced at the expence of drowning all the lowlanders) are a lot of cows farting around (production of methane), and dangit, sheep made the Sahara desert :banghead: :cuss: .
:rolleyes:

VARifleman
December 25, 2005, 04:58 PM
Ok, I'll settle this once and for all.
Lets say we have 1000 kg heavy material as uranium with density of 19 050 kg/m^3 and 1000 kg of light material as cork with density of 340 kg/m^3.
As we are weighting these in air, the the density of air is 1.239 kg/m^3,
acceleration by gravity g = 9.80665 N/kg (m/s^2) (International standart).

So uranium has the volume of Vur = 1000 kg / 19 050 kg/m^3 = 0.05249343832 m^3;
Volume of cork Vcork = 1000 kg / 340 kg/m^3 = 2.94117647059 m^3

Both have weight by gravity of 9806.65000 N
Archimedes's force (law of buoyancy): F = Rho(air) * Volume * g
Uranium : F = 1.239 kg/m^3 * 9.80665 N/kg * 0.05249 m^3 = 0.63782 N
Cork : F = 1.239 kg/m^3 * 9.80665 N/kg * 2.94118 m^3 = 35.73659 N

So the uranium has REAL weight in air Wur = 9806.01218 N
cork has REAL weight in air Wcork = 9770.91341 N

So cork IS LIGHTER as we are weighting them in AIR (you cannot discard that). A ton of cork weights 0.358 % less than a ton of uranium.

take that:neener:

They didn't teach you in school that we are actually not in vacuum, but in air and it does have a weight thus also a uplifting effect? Why do you think the Zeppelins fly, by faith? You know, when the body has a very close density to air or even less the body can have NEGATIVE weight even if it's mass is measured in tons.

HERSELF, if to chew letters then the "thing" that prevents you from burning up is Earth's magnetic field and ozone layer. Without atmosphere the Earth would be as warm as any other plain rock in the space and have close to zero habitability (including the definite and felt lack of anything worth to breath).

EDITED: I have 2 formulas for calculating the weight of bodies:
W [N] = 9.80665 * mass [kg] - 12.15044 * Volume [m^3] or
W [N] = 9.80665 * mass [kg] * (1 - 1.239 / Densitybody [kg/m^3])

So, if mass is constant, the bigger volume/ lesser density the smaller weight.
.3% difference for one of the densest materials versus a very low density material. That doesn't begin to make one bit of difference in our discussion. Remember that we are engineers, not mathematicians.

Herself
December 25, 2005, 07:19 PM
Medusa has blamed sheep for the Sahara desert!

[CUE Spaghetti Western Music, up and then under]

[Stage-whispers through teeth:]
...So, Medusa...
[SFX: large bell tolls once, in distance]
...you'd be a cattleman, then?

Me, I'm a rocketeer.

That's not going to be some kind of a ...problem..., is it?

[SFX: large bell tolls once again, louder than before]
[MUSIC up and over]
[fade to black]
:neener:

--The Woman With No Name

Medusa
December 26, 2005, 04:49 AM
Varrifle,
I was taught to take as much variables as needed into account, and buoyancy was definitely one of them. If I'd regard this my work's results would be regarded also, so habit it is.
OK lets go more drastic, say you have a 1 kg helium balloon and 1 kg brick, which one hits the ground first if released at same altitude? I'll bet a buck to that the helium balloon doesn't hit the ground at all, at first.

If to take the "engineer's way" and assume that two bodies with equal mass have equal weight then it should be so in any environment. Air is quite thin so let's replace it with water with density of 1000 kg/m^3. So if to come back to my example with cork and uranium, the cork will have weight W = -19036.47 N and uranium will have weight W = 9291.9 N . The difference is close to 300% now instead of 0.3% (so the amount of cork will have the acceleration of 2 g UP instead of 1 g DOWN).
Can you feel the difference now? IF the equal masses would mean equal weights then none of this wouldn't be true, but it is, so who's wrong? I remind you that the weight is the summarum force's projection on the axis that connects the Earth's and body's centres of masses and the positive direction is down (ie the body is pulled towards Earth).

Sorry, Herself, I'm not a western man type, currently rather a snowman type (a little below 0 C currently, outside, but funny, usually it's -20 or so C at this time of year). :rolleyes: Heh, a rocketeer? Shoulder launched SAM should be sufficient :eek: :D

Sorry girl, I'm more like technology type (and yes, hope to study engineering also some day). You seem to have plenty of wit and cunning, and sarcasm :scrutiny: Like ya, but I'm already taken :neener:

72Rover
December 26, 2005, 11:06 AM
I grew up in the Southern Philippines (Davao City). By way of celebrating Christmas or New Years it's generally tradition to fire off your firearms into the air at midnight. As a consequence about a dozen people get killed every year from bullets falling out of the sky. One New Year's our house actually took 3 hits from two different calibers.

In some countries, this is called "happy fire"...and yes, folks get killed. In other cultures, different things are given flight. In Italy on New Year's folks get killed by falling *furniture*....

Several years ago, I was standing out front of my house on a then-quiet New Year's Eve. There was no noise, other than the unmistakable sound of a small, metalic object impacting the asphalt a short distance away.:eek:

Cheers

GigaBuist
December 26, 2005, 08:04 PM
Herself (and others), it's generally a bad idea to argue terminal velocity issues with a skydiver. They've sorta looked into the issue a few times. :)

Weight does matter. SkyDaver posted about his change in speed after gaining weight. A guy I used to jump with was heavier than most and he wore a big old flappy suit to help him slow down for formations. Another, very small (and pretty!), woman had to put lead around her belly to keep up with others.

Ever seen jumpers play with a tennis ball in the air? They're filled with lead, and for a good reason.

Only did it 14 times myself, but I hung around a dropzone for a whole summer and got myself educated on the subject. Those folks know gravity, wind, and terminal velocity like a fish knows water.

Argueing terminal velocity with a jumper is like an anti-gun type arguing ballistics with us! :D

Art Eatman
December 26, 2005, 08:53 PM
"I can't believe I read the whole thing..."
"I can't believe I read the whole thing..."

Yup.

And Alka-Seltzer don' help none...

:D, Art

Herself
December 27, 2005, 11:39 AM
A 0.3% variation (in weight vs. mass due to density) is no variation at all for most purposes and even more so when it comes to heavy objects falling in the general vicinity of precious me. Just say no to objects falling with great energy!


Sorry, Herself, I'm not a western man type, currently rather a snowman type (a little below 0 C currently, outside, but funny, usually it's -20 or so C at this time of year). :rolleyes: Heh, a rocketeer? Shoulder launched SAM should be sufficient :eek: :D

Sorry girl, I'm more like technology type (and yes, hope to study engineering also some day). You seem to have plenty of wit and cunning, and sarcasm :scrutiny: Like ya, but I'm already taken :neener:

Ummm, Slim? [hoarse stage whisper] Y'all seem to have mistaken good-natured ribbing for an invitation.

Sorry back: I am almost certainly old enough to be your Mom and I have a perfectly (or at least adequately) good boy-type person at home already. If I had two, they'd just fight. :p It's like tomcats.

--Herself

Brad Johnson
December 27, 2005, 02:29 PM
So, if this week was next week last week, then what would this week be if last week was next week?

If normal people think wierd people are wierd, then what to wiered people think is wierd?

If your son married a woman, and you married the woman's daughter, that would make you the grandfather of your son's wife's daughter. Does that mean you are your own grandpa?

So many questions, so little beer...

Brad

Matt G
December 30, 2005, 06:02 PM
An excellent practical analysis of this was done by Julian Hatcher in the 1920s. Hatcher's Notebook (http://www.amazon.com/gp/product/0811707954/qid=1135983222/sr=8-1/ref=pd_bbs_1/002-2115401-7003250?n=507846&s=books&v=glance) is worth EVERY PENNY you pay. Fascinating to those of us who have very little math ability, but does include the math for you engineer types. Sometimes, math models need to be proven with machineguns pointed straight up and fired off a pier with a stopwatch and a dozen observers under a steel roof watching for splashes. :)

http://www.thehighroad.org/attachment.php?attachmentid=33228&stc=1&d=1135983678

pax
December 30, 2005, 06:20 PM
Wow. This thread is still going ...

Plainly we need an Energizer Bunny smiley.

pax

Brad Johnson
December 30, 2005, 06:24 PM
Wow. This thread is still going ...

Plainly we need an Energizer Bunny smiley.

pax

Nah, somebody would just shoot it and eat it.

Brad

Fly320s
December 30, 2005, 06:52 PM
Energizer? Everyone knows that Duracell has a better power-to-weight ratio, but neither one can compete with the tactical capabilities of Surefire's lithium batteries. :neener:

Taurus 66
December 30, 2005, 07:01 PM
hmm ... I wonder if Duacell and Enerizer batteries with similar weights will have different masses. :rolleyes:

KadicDeshi
December 30, 2005, 07:19 PM
Trapperjohn, VARifleman, if I may?

Don't feed the trolls.

If somebody's got it in their head that a constant times a constant equals a variable, then you ain't gonna convince 'em otherwise on the internet.

Especially when they don't want to be convinced.

As for the rest, well, fluid dynamics was never my forte. Almost set me back a semester graduating. I'll let the rest of you gals and fellas figure it out and you can get back to me. :D

Barrett

JohnBT
December 30, 2005, 08:53 PM
"say you have a 1 kg helium balloon"

Okay, but at what temperature? Cold enough to make the helium a liquid? ;)

My high school physics teacher worked with Von Braun. He was an interesting fellow and even got me a one-day tour of the Goddard Space Flight Center. Unfortunately, four years of being a physics major wasn't nearly as entertaining.

John

cz75bdneos22
December 30, 2005, 11:07 PM
tomorrow...it's showtime folks...
i've got my kevlar helmet on...J/K
a safe end of the year, and we'll be inside 10 min till midnight...
here in Brownsville, Texas...Saludos!:D

No_Brakes23
December 30, 2005, 11:58 PM
Well there's only one thing worse than being John Cleese, but THR won't allow me to stoop to that level - Jim's Python I certainly hope you aren't basing your negative opinion of Cleese on the "Revocation of Independence" hoax email that he had nothing to do with.

http://www.snopes.com/politics/satire/revocation.asp

If you got other reasons to dislike him, cool, but I hate when people trot this and other nonsense (Target is owned by the French, Fonda got POWs beaten, etc,) out like it was true.

RioShooter
December 31, 2005, 01:55 AM
tomorrow...it's showtime folks...
i've got my kevlar helmet on...J/K
a safe end of the year, and we'll be inside 10 min till midnight...
here in Brownsville, Texas...Saludos!:D

I live in Brownsville also. I haven't stepped outside at midnight in over 10 years.

For those of you that don't know, Brownsville sounds like a war zone at midnight!
:eek:

Medusa
December 31, 2005, 03:29 AM
"say you have a 1 kg helium balloon"

Okay, but at what temperature? Cold enough to make the helium a liquid?

My high school physics teacher worked with Von Braun. He was an interesting fellow and even got me a one-day tour of the Goddard Space Flight Center. Unfortunately, four years of being a physics major wasn't nearly as entertaining.

John
Standart conditions, of course :cool: You've seen any kid playing outside with liquid helium balloon? :rolleyes:

Vow, that tour must have been the coolest thing on Earth. Envy you on that.

If somebody's got it in their head that a constant times a constant equals a variable, then you ain't gonna convince 'em otherwise on the internet.
Nothing's constant. Well, maybe people's stupidity (small hint to the upper altitude, ie the goverment).:mad:

Sunray
December 31, 2005, 03:49 AM
"...will a bullet fired directly vertically kill you when it comes back down..." No. It won't come straight back down. Ballistics applies. Read Hatcher's Notebook.

Taurus 66
December 31, 2005, 03:57 AM
It's amazing how a topic so meaningless as to its relevancy within current matters can still live on. It's either due to "New Years Eve" festivities or "President's Day" for all high schoolers, uhh ... Nope! Or it could be some newly formed union strike in colleges which could in itself aid in keeping this a perpetuating bit (didn't know this existed amongst the student bodies). It all depends on just how many of them have enough free time and are in desperate need of beer and other pleasures of the flesh.

McCall911
December 31, 2005, 08:35 AM
According to the NRA Firearms Fact Book (published 1964) the army did testing on bullets in free fall and determined the drag factor of the bullet (BC) is the factor that determins the speed of a falling bullet. The only force acting on a bullet fired straight up @ 90 degree is gravity. It will gain speed until drag force equals the pull of gravity, at which point the bullet will stop gaining velocity. They calculate a 30-06 fireing a 180 gr PSP bullet will reach a altitude of 10120 ft. The max velocity of the bullet in fall will then depend on its attitude as it drops. A bullet can fall base first, turn over and fall point first, or tumble. They calculated the terminal velocity would be 180 fps for one tumbling, 323fps base first and 457 fps for a bullet fallng point first

That's really informative, Ol' Joe. Thanks.
But I probably don't need to add that. in addition to the air drag on the way back down, we can't neglect the effect of wind on the bullet as it falls.
So now we have to ask: Is a 180 gr '06 bullet going to penetrate skin, flesh and bone at 180, 323, or 457 fps?

230HB
December 31, 2005, 09:01 AM
Straight up or on an angle .... Kill or injure doesn`t even enter into the equation. Assume every round can kill or injure and if you don`t know where it will stop the shot just shouldn`t be taken.

1911Tuner
December 31, 2005, 09:51 AM
It's amazing how a topic so meaningless as to its relevancy within current matters can still live on. It's either due to "New Years Eve" festivities or "President's Day" for all high schoolers, uhh ... Nope! Or it could be some newly formed union strike in colleges which could in itself aid in keeping this a perpetuating bit (didn't know this existed amongst the student bodies). It all depends on just how many of them have enough free time and are in desperate need of beer and other pleasures of the flesh.

Yeehaa! I can't believe this one's still got breath either, Taurus.

Okay...Here's the straight fact of the matter. Assuming a perfect, 90-degree descent, a .22 rimfire bullet (40 grains)falling from 2,000 feet will sting, and maybe break the skin...maybe...but an 8 gauge round lead ball (2 ounces) falling from 2,000 feet will kill or cripple. Simple, what?:rolleyes:

cz75bdneos22
December 31, 2005, 02:17 PM
dec 31 AP NewYork-

a soldier accused of firing a gun into the air that killed a mother of two standing at her window was arraigned on manslaughter and weapons charges.
Army Pvt. Danny Carpio, 23 was charged w/ 2nd degree manslaughter, criminal possession of a weapon and tampering w/ evidence. Carpio fired a gun into the air on a Queens street on Wed. night to celebrate his homecoming on holiday leave from Iraq. the bullet struck Selina Akethala, 28 as she stood at her fifth-floor apartment window.:fire:

mfree
December 31, 2005, 04:19 PM
I don't think that's got anything to do with the thread... the "brilliant lad" probably directly shot that poor woman.

redneck2
December 31, 2005, 07:16 PM
So now we have to ask: Is a 180 gr '06 bullet going to penetrate skin, flesh and bone at 180, 323, or 457 fps?

IIRC, some of the CAS rounds are about 600 fps. Hate to get hit with one of them. Seems like 457 is close enough

JohnKSa
December 31, 2005, 08:40 PM
An 8 grain pellet at 400fps packs enough oomph to shoot all the way through a small animal like a squirrel. (So I've heard--I'd never do anything like that since it's against the law to shoot squirrels with an airgun in TX. Logically enough, it is perfectly legal to shoot feral hogs and mountain lions with airguns in TX.) :rolleyes:

A 180gr .30 cal bullet travelling between 300 and 500fps would definitely ruin one's day and could certainly be fatal with a little (bad) luck. terminal velocity would be 180 fps for one tumbling, 323fps base first and 457 fps for a bullet fallng point first180fps is about 123mph which agrees well with what the skydiver posted earlier about his experiments with dropping bullets during freefall. And, as I suspected, if they remain spin stabilized, the velocity is 2-3 times faster.

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