Bullet dropped lands the same time as a bullet fired..
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spinning things do weird things. .... This is not fake, its easily duplicated on a bike wheel, where a 6lb wheel can be easily held on one finger. I think its possible this could have an effect, but it would require impossible distances to see a difference.
mcb
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Symmetric bodies that are rotating can produce lift. It is called the Magnus effect. In the case of the baseball and ping-pong ball it is the portion of their rotation perpendicular to the path of travel that generates that lift or a lateral force. The rotation changes the way the air flows around the object due to interaction of the rotating surface and the boundary layer that is attached to that surface. A bullet's rotational axis, for all intensive purposes, is paralleled to it axis of motions and thus cannot generate an force.
In cases of extremely long range shooting you can see the Magnus effect but is shows up usually as a drift to one side (depending on left or right hand rifling). Its called spin drift and is a product of both gyroscopic and Magnus effect working in concert. Gyroscopic force cause the bullet nose to move off the exact path of travel pointing the axis or rotation off the axis of flight allowing the Maganus effect to create aerodynamic force though it typical creates a lateral force not a lifting force. Strong cross winds can also generate lift or negative lift due to the Maganus effect. Any Magnus related forces are very small and are negligible for all but extremely long range shooting and even then they are a distant secondary factor to most other thing effecting the bullet in flight.
Baseballs and ping pong balls do NOT have symmetric spin relative to their direction of flight and gravity. They don’t spiral. The bottom spins in one direction relative to the airflow, the top moves in the opposite. That asymmetry is what causes the lift when the spin is backspin.
Captcurt
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Prove it. Oh, that's right. You don't have a vacuum.
1976B.L.Johns.
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Happens often to me... but that is why I am here reading the wisdom!
mcb
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It's axis of rotation is pointed at the batter's head as you indicate putting it above the line of flight that starts at the pitchers shoulder or higher depending on release while standing on the pitches mound coming down to the catchers glove at the batter's strike zone. This is enough difference between axis of rotation and path of motion to generate the late lateral movement of the slider.
danez71
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Slider don't produce lift. They're meant to drift down and laterally thru the strike zone.
Theohazard
Member
Actually, it would have everything to do with the speed of the bullet. Accounting for the curvature of the Earth, the faster the bullet travels the longer it stays aloft, even if fired from a horizontal position. This is because the curved Earth “drops off” below the bullet. So the faster the bullet goes, the more ground it covers and the more the curved Earth comes into effect.
In fact, in the real world, a bullet fired with enough velocity from an exactly horizontal position would go into orbit and wouldn’t hit the ground at all. But that would take a muzzle velocity way, way above any cartridge we have today.
denton
Member
There is also the Eötvös Effect. When shooting a trajectory that has an east/west component, you'll get a small rise or fall effect that will affect the bullet's time in flight. This is sometimes incorrectly attributed to the Coriolis Effect, which affects trajectories with a north/south component.
Only The Almighty gets perfect information. The rest of us have to put up with one degree or another of approximation.
To as good an approximation as anyone shooting any real sporting firearm at under 500 yards cares about, the dropped bullet and the horizontally fired bullet reach the ground at the same time.
Only The Almighty gets perfect information. The rest of us have to put up with one degree or another of approximation.
To as good an approximation as anyone shooting any real sporting firearm at under 500 yards cares about, the dropped bullet and the horizontally fired bullet reach the ground at the same time.
So, can you estimate velocity from bullet drop. Lets say you sight your rifle at 100 yards, or 200 yards, and measure the bullet drop 100 yards further out. Will that be an accurate measure of velocity?
I know wildcatters were doing this in the 1950's, because chronographs were huge machines. I never took their in print velocities seriously, but........
I know wildcatters were doing this in the 1950's, because chronographs were huge machines. I never took their in print velocities seriously, but........
Fine Figure of a Man
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It's a very accurate way to measure of velocity.
CoalTrain49
Member
The curvature of the earth is not a factor for any small arms cartridge/bullet in this world.
The curvature of the earth is only 8" in a mile. A 22-250 with a MV of 3800 fps drops 250" in half a mile and 1.5 seconds.
You must be thinking about missiles.
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Theohazard
Member
I understand that. You’re taking my comment out of context. Notice the comment I was directly responding to: It referenced the curvature of the Earth, so that’s what I was responding to: He incorrectly stated that bullet velocity wouldn’t be a factor in that case. But it actually would, even if it’s a small factor.
My comment was correct; even if the curvature of the Earth is a very small variable, it’s still a variable. But I removed that variable in my first post in this thread because I know it makes an insignificant difference in most cases.
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Panzerschwein
member
No way, dude.
As odd as it seems, even a .22-250 is going to hit the ground about the same time as a .22 short. BUT, it'll have traveled way farther when it does!
As odd as it seems, even a .22-250 is going to hit the ground about the same time as a .22 short. BUT, it'll have traveled way farther when it does!
Theohazard
Member
I'm going to call you out on this comment. Please reference the specific people in this thread who have displayed an unsatisfactory knowledge of physics. If you're not willing to name names and refer to specific posts, then your comment is entirely unproductive.
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Panzerschwein
member
Theohazard
Member
I agree with the point you're making, but I should add that the force of gravity is different depending on where you are on the planet. The figure 9.8 m/s^2 is just an average.
RecoilRob
Member
I'd think that you could definitively say that a particular bullet that drops less than that same one fired at a lower velocity was going faster, but trying to compare two different projectiles I'm thinking the possibility that different BC's would play enough of a spoiler to thwart any conclusions about velocity. And without knowing the velocity of one shot using more or less drop for the next one still leaves you guessing as to what it might have been. If a general BC was assigned to each bullet then you could calculate a reasonable estimation of velocity from the drop, but how accurate it would be I don't know and am thinking there is a lot of room for error.
Bullet pendulums were used way back in the pre-electrical days and could be pretty accurate. You know the weight of the pendulum, then measure how far it moved when shot. This takes 'X' amount of energy, then back calculate the bullet weight that struck it and you get the muzzle velocity needed to create it. Or a reasonable estimation thereof.
I don’t think that is correct. The REASON that bullets with a better BC drop less is BECAUSE their velocity decays less slowly. Bullets don’t generate lift.
Drop over distance is driven by velocity; drop over time is constant. BC predicts how much velocity decays. It only flattens trajectory by keeping velocity higher.
In fact, rather than needing BC to calculate velocity from drop, knowing drop at multiple distances would allow you calculate the BC of the bullet!
Fine Figure of a Man
Member
Yes
And measuring bullet drop at a given range , preferably long, will tell you very accurately what the velocity is.
It will also show you if your crony reads fast, slow or correct. Mine reads a little slow but it is consistent.
CoalTrain49
Member
Sorry, I thought you were saying it was a significant factor. My apologies. I spent 40 years making curvature and refraction calculations on the job. It's rocket science.
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