How do ik if a question is an elastic collision or inelastic collision? How do i distinguish the difference between them when i am given a question on the test?

2 Answers
Jul 11, 2018




Elastic collision
- no loss of kinetic energy
- slight change in direction

Inelastic collision
- a loss of kinetic energy
- no change in direction because the particle is absorbed by the atom that it hits

An example is an experiment that is used to prove the discrete energy levels in Bohr's model is the Franck Hertz's experiment using mercury vapor

Jul 11, 2018


If the question does not specifically indicate whether elastic collision or inelastic collision, it can be difficult. Hints below.


The main characteristic that indicates whether elastic collision or inelastic collision is conservation of energy. Conservation of energy in a collision exists only in elastic collisions. So if you able to calculate total kinetic energy before and after the collision, that will tell you. Energy can shift from one body to another in elastic collisions, but the total before = total after.

Another indication is if the question indicates something that would indicate loss of energy. Cars banging together typically bend and smash car parts. That means work is done and that work subtracts from the total energy.

I hope this helps,