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

Scene 3: Wanted Bullet Circle 

Watch a scene from “Wanted” in which a bullet is shot while moving the gun in a swing, supposedly causing the bullet to curve around the whole room. Try to answer the following questions:

What Laws of Motions does this scene defy?

What is the difference between the “curved bullet” and something like a “curve ball”? While the bullet might not be able to curve around the entire room, is it possible to shoot a bullet with a curved trajectory?

The bullet retains its speed as it passes through each person. According to the Laws of Motion, what should happen every time the bullet passes through someone?

The bullets around-the-room (circular) motion would be possible under a certain impossible situation, can you figure out what that is? 

https://www.youtube.com/watch?v=lGZQi3ODB-U 

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

This scene illustrates the First Newton’s Law of motion.  In this scene, the bullet is an object in motion. According to the first law of motion, an object in motion will remain in motion in a straight line so long as there are no other forces acting on it. Therefore it is impossible for the bullet to curve as it does without some mysterious non-existent force at work. In the same vein, the bullet goes through people which results in an impact force on the bullet; typically, when a bullet hits something it slows down and either continues until the next object or stops completely. This is in line with the First Law.  There are other topics that can be addressed, such as the effect of projectile motion and the bullets arcing downward due to gravity given enough time.  

So, is it possible to shoot a curved bullet by an approach similar to throwing a curve ball? The answer is no, why? The answer lies in the second law, F=ma. The bullet, who has a small mass, is launched with an insane amount of acceleration (after all, it goes from rest to hundreds of miles per hour almost instantaneously) shooting the gun while it is in any sort of motion would result on a straight line regardless. Meanwhile, pitchers can only reach speed of approximately 100 mph and baseball balls are heavier than bullets, so while it is possible to throw curve balls, it is not possible to shoot curved bullets.

The around-the-room behavior of the bullet resembles the effects of centripetal force. Assuming that there was something in the center of the room which causes the bullet to have centripetal force, it would be possible, but such a thing would be implausible with a regular bullet. For the concept of controlling the trajectory, perhaps an electromagnetic rail system like the ones employed in rail guns could do the trick, but again, it is highly unlikely.