A collision is a situation in which two (or more) objects hit each other, usually during a small amount of time. Collisions can be categorized by whether or not the kinetic energy of the system changes or not:
Elastic collision: The kinetic energy of the system does not change (no kinetic energy is "lost" or "gained").
Inelastic collision: The kinetic energy of the system decreases (some kinetic energy is lost, usually transforming into heat, sound, or internal energy). When two colliding objects stick together afterward, the collision is said to be perfectly inelastic.
Super-elastic collision: The kinetic energy of the system increases (some kinetic energy is gained, usually transforming from internal potential energy).
ExercisesActivities
Two bicycles initially moving toward each other get in a low-speed accident in which they bounce off each other so that each bicycle is now moving at the same speed but in the opposite direction!
1.
Choose a system for this context for which momentum is conserved. How do you know momentum is conserved for your system?
2.
For your system, does the kinetic energy change? How can you tell?
3.
What kind of collision is this? Explain.
4.
How could you change the context into a different form of collision? See if you can figure how two bicycles colliding could give you all three kinds of collisions!
