Michael T. answered • 11/11/20
PhD in Physics with 7+ years of teaching experience.
Elastic vs Inelastic collisions.
A) A rubber ball bounced off a wall at essentially the same speed in which it hit the wall.
B) A ball of clay hits a wall and sticks.
C) A bowling ball knocks over a pin.
D) After colliding head on, two marbles recoil in opposite directions.
E) A large comet hits the planet Jupiter and becomes absorbed into the gaseous layers of the planet.
F) A bullet is fired into a bale of hay and becomes embedded.
G) A cue ball hits the 8 ball, sending the 8 ball off at the same speed the cue ball hit while the cue ball stops.
Fundamentally what is the difference between an elastic and inelastic collision? The names really are the hint here. A perfectly elastic collision is one in which the objects bounce off each other and there is no loss in kinetic energy in the system. An inelastic collision on the other hand loses energy to something like a deformation or a sticking of objects together.
So I won't do all of these for you but letter a) a rubber ball bouncing off a wall at the same speed clearly is an elastic collision because there is no loss of kinetic energy for the ball in the collision process. Letter b) on the other hand is the example of an inelastic collision because clearly to stick to the wall the ball must lose its kinetic energy associated with its motion.
After those two the answers get more vague and you have to use more critical thinking about what is happening in the system, but if the kinetic energy is the same after the collision as it is before it is an elastic collision.
