Die Hard

[mtaylor]

I am hoping someone can explain this. Its a well worn movie cliche that the bad guy is pushed out a window, but he is SO bad that while he is falling he shoots upward at the hero.

If the bad guy was in outer space and fired a pistol he would be pushed backwards by the recoil. (See Outland.) If the bad guy is in free fall out the window and fires a gun, lets say holding the gun at shoulder height, wouldn't the recoil cause him to start spinning heels over head? The recoil would be a force pushing against the top of his body, making it fall faster than the rest of his body.

Is the cliche wrong, or am I?

[Taunide]

Just a guess, I suppose the air resistance would dampen the effect. Plus: the impulse is so small and short that it would not suffice to get you spinning rapidily but slowly. Simply by the difference of masses.

[Tog]

This may be better off in Small Media at Large or even OTB, so don't be too surprised if it gets moved.

The problem with the idea that a small handgun will start a person spinning comes from the fact that the human body is not rigid. Even a .44 mag can be fired one handed without affecting the position of the body. The recoil is absorbed an controlled by the arm. The recoil from a 9mm is so slight that it barely takes more than the forearm to keep the muzzle down.

The most recoil I've ever experienced in a handgun was a special load in a 454 Casull. The recoil was severe enough to rotate the gun in my hands and spin me around at the waste a full 45 degrees. Because I was expecting it to kick like that, I was ready for it and my feet didn't move, nor did my upper body lean backward very much. My hands ended up about even with my chest with the muzzle pointing downrange but the grip of the gun rotated horizontal to the ground.

My dad used to shoot a 45. Long Colt in target matches by letting it free recoil. He would rest the trigger guard on his middle finger and use the presence of his palm to steady the gun. When it went off, it would jump up and back, but the bottom of the grip would hit his finger and the force would close his hand around it. Granted he's got some freaky big hands, but the recoil alone was not enough to even move his whole arm.

The next guy in line to shoot it said he didn't want anything to do with it.

Now a big rifle might create that effect, because if held properly, it's braced on the shoulder. Recoil absorption in the body takes place here from mass alone, and a little give with the hips.

The most I've ever taken there was probably a .577 Nitro Express "light model" This was designed for head on shots at charging elephants at ranges of 30 meters. When I shot it, I leaned way out over my lead foot with almost no weight at all on my rear foot. It still stood me up straight and I had to take one step back with each foot. I weighed about 200 pounds at the time. We each fired 10 of those that day. I have no doubt that one of those would spin a person in freefall, air or not.

[Taunide]

watch?v=-EVqT3XEzss
That one??

[Tog]

That one is actually bigger. Well the same diameter but faster so far more recoil. Still, if you watch that set of clips for a while, you can see one guy that actually knows what to expect and he handles it well.

[DaveC426913]

The problem with the idea that a small handgun will start a person spinning comes from the fact that the human body is not rigid. Even a .44 mag can be fired one handed without affecting the position of the body. The recoil is absorbed an controlled by the arm. The recoil from a 9mm is so slight that it barely takes more than the forearm to keep the muzzle down.
While true, all this is irrelevant. You arm absorbs the recoil because it is connected to the chest, which is (eventually!) connected to the leg, which is connected to the ground. Take away the ground and it is simply momentum of bullet applied to body mass.

Try firing that gun while sitting on a frictionless office chair and you will surely turn.


Now, all that being said, one stabilizing factor on a falling body is that it will tend to assume a broadside-to-wind position. (This is well-known to anyone who has tried to canoe in a strong wind. The canoe will invariably turn broadside unless you're very heavy on the paddle.) The gun may send him spinning but the air resistance might be enough to stabilize him.

[mtaylor]

Thanks everyone. Its hard to imagine that air resistance would be enough. Imagine firing a gun with a strong wind at your back. You'd still feel the recoil of the pistol.

[DaveC426913]

Thanks everyone. Its hard to imagine that air resistance would be enough. Imagine firing a gun with a strong wind at your back. You'd still feel the recoil of the pistol.Of course you would, but this is about whether you'd rotate.

You would rotate, yes, but the wind force would rotate you back (just like the canoe in the wind).

[AstroSmurf]

Sounds like the way to do zero-G maneuvering with a gun would be to point it towards (but missing, preferably) your feet. That would minimise the angular momentum, and give you a stable firing platform. Just wait until the spin puts the right area of space in your sights and fire away.

ObReference: The enemy gate is down!

[Taunide]

Maybe a little off-topic but I always liked the movies from Skylab when they were actually able to do a spread eagle without touching the walls. I am so envious and would have loved to do something like that. You might have been able to test your theories with a bottle of compressed air up there.

[Tog]

While true, all this is irrelevant. You arm absorbs the recoil because it is connected to the chest, which is (eventually!) connected to the leg, which is connected to the ground. Take away the ground and it is simply momentum of bullet applied to body mass.

So the mass and resistance of the arm wouldn't dampen the spin? I'm thinking of something that doesn't really have much recoil, like a 9mm or .45; something that can be controlled easily with one hand. I can understand how a rigid body would transfer the momentum from any shot, but why would the mass in the arm not act as a cushion?

Tone clarification: I'm not really being argumentative. If this is really the case, I'd like to know why I'm wrong about it. I can see it with a big handgun, they have enough recoil to spin a person around anyway. I've done a lot of shooting and martial arts. I've always had a pretty good grasp of what my body was doing and how it was doing it when it comes to sudden motions. I just don't ever recall something like a 9mm (in an auto) moving my shoulders at all.

I need a highspeed camera and a box of shells. And more grant money to continue research. :)

[DaveC426913]

So the mass and resistance of the arm wouldn't dampen the spin? I'm thinking of something that doesn't really have much recoil, like a 9mm or .45; something that can be controlled easily with one hand. I can understand how a rigid body would transfer the momentum from any shot, but why would the mass in the arm not act as a cushion?
I guess you're right. The arm is not rigid and could absorb a little bit of the motion. But idea for firing a gun accurately is to hold your arm as rigid as possible or your aim is spoiled. To absorb any significant momentum, the arm would have to be limp.

[Tog]

I guess you're right. The arm is not rigid and could absorb a little bit of the motion. But idea for firing a gun accurately is to hold your arm as rigid as possible or your aim is spoiled. To absorb any significant momentum, the arm would have to be limp.

Actually that's not right. You want to be relaxed. Well, as relaxed as possible. The more effort that is placed making the arm rigid, the more the muscle tremors will be transferred to the hand. Even squeezing the grip harder between shots can change the point of impact. A tighter grip make the impact lower. This is why my dad used that free recoil method I described above.

In a two hand grip, the non firing arm is held stiff but it is used to just keep the gun at the right height. In one arm shooting, the arm is never held with the elbow locked, wi the the majority of the support coming from the deltoid.

Now, it wouldn't be the first time that the way I was taught to do something it notably different than standard, so my understanding of the grip might be a good deal different. That might be why I'm confused.

[DaveC426913]

The more effort that is placed making the arm rigid, the more the muscle tremors will be transferred to the hand.
... In one arm shooting, the arm is never held with the elbow locked, wi the the majority of the support coming from the deltoid.

OK, I overstated it, I didn't mean as rigid as possible, in the sense of locking the elbow. I simply mean in the sense you don't want the gun to kick, causing your hand to fly over your head.

If you think aboujt how loose you'd have to hold your arm to absorb all the energy so that, in sitting on an office chair, you wouldn't spin, you'd have to have your arm almost limp.

[jj_0001]

I guess you're right. The arm is not rigid and could absorb a little bit of the motion. But idea for firing a gun accurately is to hold your arm as rigid as possible or your aim is spoiled. To absorb any significant momentum, the arm would have to be limp.

The stiffness of the arm is not relevant. You're holding on to the gun, you're not dropping it, the only difference is how fast the momentum gets to the whole system.

I vote for 'acquiring spin', but I have no idea of the amount of momentum from a pistol shot, OR the moment of inertia of a falling body, so I have no idea how much spin.

[Divine Wind]

So the mass and resistance of the arm wouldn't dampen the spin? I'm thinking of something that doesn't really have much recoil, like a 9mm or .45; something that can be controlled easily with one hand.

Dave is correct, IMHO. The First Law of Thermodynamics and the Third Law of Motion both come into play here. If I may expand upon Dave's statement, your arm is acting like a shock absorber, but the energy of the shot is still transfered to your entire body. A large adult has no problem controlling the shot without flipping over because of the gravitational attraction of their mass holding them to the ground. If they stood up in a canoe floating on water or in a little red wagon firing along the axis of the wheel's rolling motion then it would be proven that the energy of the shot is transfered through the body to everything it contacts.

To answer the question, a falling body is basically frictionless. Air resistance is applied equally on every square inch of the body, but due to the body's irregular shape (e.g. torso and head atop two legs) force applied to one end won't produce the same exact results as the other end. In short, the legs are have less air resistance than the torso. Even so, a person falling flatly who fires a pistol like in Die Hard would start to spin both backwards head first (because the pistol is raised to eye-level for aiming) and to the right (IIRC, the shooter was right-handed).

[DaveC426913]

Even so, a person falling flatly who fires a pistol like in Die Hard would start to spin both backwards head first (because the pistol is raised to eye-level for aiming) and to the right (IIRC, the shooter was right-handed).I still think though, that air resistance would return the shooter to the horizontal position.