Collisions (Also seen in GCSE Physics 2)
There are two types of collisions; in both cases the momentum is conserved.
Elastic – kinetic energy in conserved, no energy is transferred to the surroundings
If a ball is dropped, hits the floor and bounces back to the same height it would be an elastic collision with the floor. The kinetic energy before the collision is the same as the kinetic energy after the collision.
Inelastic – kinetic energy is not conserved, energy is transferred to the surroundings
If a ball is dropped, hits the floor and bounces back to a lower height than released it would be an inelastic collision. The kinetic energy before the collision would be greater than the kinetic energy after the collision.
Before After
In the situation above, car 1 and car 2 travel to the right with initial velocities u1 and u2 respectively. Car 1 catches up to car 2 and they collide. After the collision the cars continue to move to the right but car 1 now travels at velocity v1 and car 2 travels a velocity v2. [ is positive]
Since momentum is conserved the total momentum before the crash = the total momentum after the crash.
The total momentum before is the momentum of A + the momentum of B
The total momentum after is the new momentum of A + the new momentum of B
We can represent this with the equation: