What would happen if...

[mugsie]

What would happen if a gun was set up such that it would be impossible for it to recoil. Take a rifle for instance, suppose it was locked down so that it couldn't recoil back, or up. It was phisically impossible for the barrel to move in any direction. Then it was fired.

Since physics dictates that for every action there must be an equal and opposite reaction, does the barrel then blow up? There has to be some place for the pressure to go, and since it can't go back something has to give. What? I would suspect the barrel would rupture and it would become a bomb.

What say ye?

 

[Manco]

Since physics dictates that for every action there must be an equal and opposite reaction, does the barrel then blow up?

No, just like it doesn't blow up after it stops moving backward when fired normally. The backwards momentum, or more properly recoil impulse, is ultimately imparted to the Earth in both cases. It's just that since the Earth is extremely large in comparison, nobody notices any effect.

There has to be some place for the pressure to go

Yeah, it goes out the muzzle after the bullet, making a BANG sound as it equalizes with the surrounding atmospheric pressure. In order to blow up the gun, you'd have to stop the bullet from leaving the muzzle.

 

[mrnkc130]

Since physics dictates that for every action there must be an equal and opposite reaction, does the barrel then blow up? There has to be some place for the pressure to go, and since it can't go back something has to give.

there would still be an opposite reaction, just because you cant see anything moving doesnt mean there isnt pressure or force on something acting equally in opposition.

 

[Aren't we all]

a caldwel lead sled?

 

[Blackbeard]

I think you're confused on what "equal and opposite reaction" means. It only means that the force moving the bullet forward is equal to the force moving the gun backward. Not all force results in movement.

Think of it this way -- if you push on a door that is not latched, the door opens. If the door is latched, does your arm blow up? No. Motion results when inequal forces are imparted to an object. You push on a latched door, and the latched door pushes back on you equally. No motion. Unlatched door cannot push back equally -- motion -- door opens. Same idea with gun against wall vs. gun against shoulder. The wall can push back equally, your shoulder cannot.

 

[Manco]

I think you're confused on what "equal and opposite reaction" means. It only means that the force moving the bullet forward is equal to the force moving the gun backward. Not all force results in movement.

While this is true in general, in this hypothetical case the planet Earth is in fact moved very slightly when the gun is fired. While the end result is no net change in the system as a whole, for a moment the Earth is perturbed a little bit. Just because we can't measure the pitifully small amount does not change the physical reality.

Think of it this way -- if you push on a door that is not latched, the door opens. If the door is latched, does your arm blow up? No.

Theoretically, for the purposes of this discussion it could "blow up" (or rather shatter) in your example, given sufficient force--this is analogous to a barrel obstruction.

Motion results when inequal forces are imparted to an object.

That's not true at all, and it would violate one of Newton's laws, which says that reaction forces are simply equal and opposite. So in reality, the forces are equal whether or not there is motion.

You push on a latched door, and the latched door pushes back on you equally. No motion.

Actually, there is no motion because both objects are part of the same system, the door being attached and latched to the house or building, and you being attached by friction (enabled by gravity) to the same structure.

Unlatched door cannot push back equally -- motion -- door opens.

No, it pushes back on you equally hard due to inertia, transferring a torque through your feet into the structure, and then from the structure into the Earth--it's just too small to notice or measure due to the size of the Earth, that's all. What I'm saying here is that the opposing forces are equal but that doesn't necessarily mean that the resulting velocities of the objects will be, which depends on their masses (the Earth being far more massive than the door, of course).

Same idea with gun against wall vs. gun against shoulder. The wall can push back equally, your shoulder cannot.

But in this example the bullet moves regardless of whether your shoulder does or not--think about that. In truth, both the bullet and the Earth move, whether something in between also moves or not...actually, even the stiffest materials attaching the gun to the Earth will move, although it may be too little for us to notice. However, in the end the bullet and Earth are part of the same system, which is bound by gravity, so there is no net change in momentum, just a transitory wiggle in the Earth's rotation and/or motion that is too small to measure or matter. The very same thing happens when you walk or drive a car, by the way.

 

[youngda9]

The OP made me LOL..HILARIOUS. Will the earth's rotation reverse, resulting in time being inverted and we all go back to childhood...

Your question was answered by post #2.

 

[Superlite27]

Will the earth's rotation reverse, resulting in time being inverted and we all go back to childhood...

Only if we face eastward and fire all our weapons simultaneously.

 

[Rshooter]

Put that puppy on a lead sled and lock it down it will eventually cause damage to a wood stock. As others have said, even though you see no recoil the force is going somewhere and the stock is taking some of it.

 

[FIVETWOSEVEN]

one thing i've wondered is if some of the guns that work by recoil would work, like the single trigger O/U shotguns.

 

[Shadow 7D]

No, that is know problem with the benelli or is it beretta, inertia system, if you deprive it of energy, the bolt won't cycle.

 

[The Lone Haranguer]

The stock would break within a few shots if no movement whatsoever is allowed. I've heard of stock cracking with certain rigid rests that are weighted down with bags of shot.

 

[Coyote3855]

My uncle broke the stock on a Winchester .30-30 by setting it vertically, butt down on a wooden porch and pulling the trigger. One shot was all it took.

 

[FLAvalanche]

Will the earth's rotation reverse, resulting in time being inverted and we all go back to childhood...

Only if the firearm used is a .45 ACP.

 

[ForumSurfer]

Only if the firearm used is a .45 ACP.

It also explains the theory that too tight of a grip and locking your arms will result in your heart exploding when firing 10mm.

 

[Chemistry Guy]

From an ideal physics perspective, the second post is correct concerning the conservation of momentum, although a more practical explanation would say that the momentum of the object was transferred into the momentum of individual atoms/molecules in the form of heat. Unless the material is an impossibly rigid crystal, the energy of the recoil compresses the intermolecular springs that hold the material together. Applying a huge compressive stress to the stock of the gun is generally not a good thing, as they are designed to fire with a somewhat elastic medium absorbing the recoil.

 

[mack]

Thank goodness - I was worried about all those fifty caliber machine guns mounted on tanks blowing up.

 

[chaplain tom]

I work as a track chaplain at a major dragstrip and I watch very powerful dragsters (Top Fuel) with over 8000hp launch all the time. The concept here is very similar. I laugh at the idea of "moving the earth" even a little bit. The earth is too huge and the powers of the universe too great for anything man made to have any affect on the earth's movement at all.

When a dragster can "hook up" (which can never be completely accomplished) the car just moves forward quicker and accelerates faster. More of the power that launched it is able to propell it forward because less of the force is wasted. Theoretically wouldn't the same thing happen with a bullet fired out of the barrel of a gun? Providing that the "hardware" of the gun in question was made out of strong enough material in ample quantities, i.e. thickness of barrel and stock and the anchoring system itself, wouldn't you just get more muzzle velocity since the gun like the earth didn't move? The force has to go somewhere, why not out the end of the barrel?

 

[Shadow 7D]

Yes, but

the time involved is thousands of a second, so I don't know how much gain you would get, look at old cannon, the developed rolling carriages, and MASSIVE hydraulics by WWI to handle the recoil because anything less simply got mangled, if it was such a gain, I would have thought they would have worked to capture it.

 

[chaplain tom]

I was only thinking in theory here. I realize we cannot really capture all the power available to us with firearms. Some is going to be wasted and to try to restrain it all is futile because we don't have the technology to prevent total destruction of the weapon itself if we tried to make use of ALL the force.

 

[Purgatory]

This thread KILLED me.

I choose..................................post......#8.

Is this a poll?

 

[chaplain tom]

This thread KILLED me.

I choose..................................post......#8.

Is this a poll?

I pray that all the comments about moving the earth were sarcasm.

 

[Manco]

From an ideal physics perspective, the second post is correct concerning the conservation of momentum, although a more practical explanation would say that the momentum of the object was transferred into the momentum of individual atoms/molecules in the form of heat.

You're right, of course, but keep in mind that most people don't even know what heat really is, so I tried to limit the discussion to the conservation of momentum (ideal physics edition), which most people struggle with enough as it is (evidently, given some of the posts). Once they understand that, then you can tell them what you didn't tell them before, just like in a physics course when you teach students about Newtonian mechanics before getting into relativity theory.

 

[Blackbeard]

Quote:
Originally Posted by Blackbeard
I think you're confused on what "equal and opposite reaction" means. It only means that the force moving the bullet forward is equal to the force moving the gun backward. Not all force results in movement.

While this is true in general, in this hypothetical case the planet Earth is in fact moved very slightly when the gun is fired. While the end result is no net change in the system as a whole, for a moment the Earth is perturbed a little bit. Just because we can't measure the pitifully small amount does not change the physical reality.


Quote:
Originally Posted by Blackbeard
Think of it this way -- if you push on a door that is not latched, the door opens. If the door is latched, does your arm blow up? No.

Theoretically, for the purposes of this discussion it could "blow up" (or rather shatter) in your example, given sufficient force--this is analogous to a barrel obstruction.


Quote:
Originally Posted by Blackbeard
Motion results when inequal forces are imparted to an object.

That's not true at all, and it would violate one of Newton's laws, which says that reaction forces are simply equal and opposite. So in reality, the forces are equal whether or not there is motion.


Quote:
Originally Posted by Blackbeard
You push on a latched door, and the latched door pushes back on you equally. No motion.

Actually, there is no motion because both objects are part of the same system, the door being attached and latched to the house or building, and you being attached by friction (enabled by gravity) to the same structure.


Quote:
Originally Posted by Blackbeard
Unlatched door cannot push back equally -- motion -- door opens.

No, it pushes back on you equally hard due to inertia, transferring a torque through your feet into the structure, and then from the structure into the Earth--it's just too small to notice or measure due to the size of the Earth, that's all. What I'm saying here is that the opposing forces are equal but that doesn't necessarily mean that the resulting velocities of the objects will be, which depends on their masses (the Earth being far more massive than the door, of course).


Quote:
Originally Posted by Blackbeard
Same idea with gun against wall vs. gun against shoulder. The wall can push back equally, your shoulder cannot.

But in this example the bullet moves regardless of whether your shoulder does or not--think about that. In truth, both the bullet and the Earth move, whether something in between also moves or not...actually, even the stiffest materials attaching the gun to the Earth will move, although it may be too little for us to notice. However, in the end the bullet and Earth are part of the same system, which is bound by gravity, so there is no net change in momentum, just a transitory wiggle in the Earth's rotation and/or motion that is too small to measure or matter. The very same thing happens when you walk or drive a car, by the way.

Way to overpost it, man. Since the movement imparted to the Earth is negligible, I felt it unnecessary to mention in my one-paragraph explanation of why your gun won't blow up if you brace it in place. Tell me, does your screen move a little bit to the right when you see this guy? :banghead:

 

[Manco]

Way to overpost it, man. Since the movement imparted to the Earth is negligible, I felt it unnecessary to mention in my one-paragraph explanation of why your gun won't blow up if you brace it in place. Tell me, does your screen move a little bit to the right when you see this guy? :banghead:

There is no reason to get bitter and personal. The reason that I went to such lengths in my response to your post was that you gave explanations of certain physical phenomena that seem intuitively correct to many people but violate Newton's Third Law of Motion, and this required a detailed response to explain why each and every thing you said--all in one short paragraph--was wrong in some way (and simply ignoring the Earth's negligible perturbation doesn't explain everything you said). I suppose that I could simply have said that your whole post goes against the conservation of momentum, but that sort of "drive-by" commentary doesn't hold much water in forums where one is usually expected to back one's claims that somebody else's entire post is in error. Well, at least I wouldn't like it if somebody did that to me. On the other hand, if somebody nailed me on every point I tried to make, correctly, then that would be a reminder that I'd better make sure that I have my facts straight before posting next time if I don't want that to happen again.

And no, I'm not chastising you now. To me it's no big deal--somebody posts something factually or logically incorrect, and I correct the error. If I post something incorrect (and who hasn't?), then I would expect it to be corrected, as well. I doubt that most people remember who said what for long, but hopefully they'll take away a better understanding of the subject.