Lesson 4: Test your Knowledge on Laws of Motion – Part 8

Scene 7:  Superman Returns Bulletproof

Watch a scene from the movie “Superman Returns” in which Superman is shot by a machine gun and then shot in the eye, yet receives no damage. Answer the following questions:

What Laws of Motion are broken?

Give a breakdown of the circumstances in the scene in relation to the equation Force equals mass times acceleration (F = ma).

While Superman is shot in the chest with the machine gun, he is shot with a pistol on the eye. In both cases, the bullet is crushed as if it smashed against an incredible force. Is the scale/size of the object an important factor in determining the force? Would shooting him in the eye with the machine gun have more of an effect?

https://www.youtube.com/watch?v=C2gQo-0VW5c 

Click here to read a discussion on the scene and compare your thoughts.

This scene illustrates the First and Second Newton’s Laws of motion. In this scene Superman is being shot repeatedly by a machine gun and is then shot in the eye. What laws are broken in this scene? The first and second laws come to mind. In terms of the first law, an object remains in motion unless acted on by another force. However there is no evidence that Superman has actually done anything but stand there, as such, it should be impossible to stop the bullet. Of course, in that situation you could think of it as if the bullet was hitting iron or some other tough material, which of course breaks other anatomical factors. For the second law, think of the scene in terms of F=ma. As discussed in the Wanted scene, bullets have huge acceleration, which results in a massive force considering their small mass. Now if you notice, Superman is again not moving in the slightest, and the mass of the eye is small (which does not matter in the absence of acceleration, at least not classically), so in reality the force his eye is exerting is zero; yet the fact the bullet gets crushed means that the force the eye is exerting is higher than the bullets.

Now consider that the two phenomena observed: (1) Superman is shot in the body with a chain gun and the bullets bounce off; and (2) Superman is shot in the eye with a handgun and the bullet is crushed onto itself. The muzzle speed of a particular type of chain gun is 1800 mph while that of a random 9mm gun is 762 mph. Is this phenomenon, in which the chain gun bullets bounce off the body and the small handgun bullets are stopped making sense? For argument’s sake, assume that the bullets are the same mass. The chain gun is going at higher velocity than the handgun, therefore, according to the equation of momentum, momentum = mass x velocity (p = mv) the momentum is higher for the chain gun bullets. The fact that the bullets bounce off Superman means that the force/momentum from Superman’s body is higher than the bullets, therefore they ricochet; it would be like the bullets where hitting a wall of strong metal; whereas in the (2) case, the bullets are hitting the softer eye and get crushed. This makes sense since the eye is much softer than skin. This suggests that his eye is just barely strong enough to counter the bullet’s force. What do you think would happen if he was shot in the eye with the chain gun then? In this scenario the bullet would actually go through, but seeing as this isa movie, it would likely be ignored and the eye would still stop the bullet.