From (Graham Grieder)

In Unit A when talking about momentum (p), we visited the difference between Elastic and Inelastic collisions.

What is an Elastic Collision ?

When you think of an elastic, you think of something that moves around when stretched but returns to its original form after. A similar idea is used here. An Elastic Collision occurs when objects collide and bounce back without deforming. The key to the Elastic Collision is that there is NO ENERGY LOST. Both energy and momentum are conserved in this collision.


The two objects can have different velocities and can even have different masses as shown above. Notice that the energy is being transferred from one object to another conserving energy.

What is an Inelastic Collision ?

There are a couple differences here between the two collision types. One of the differences is that in an Inelastic Collision, the objects collide but deform in some way instead of just bouncing back. This causes a loss in energy, there for ENERGY IS LOST. In this case only momentum is conserved in this particular collision. This can also be known as a Hit and Stick Collision.



Just as before, the velocities and masses may be different for this effect to occur. A good example of this is a car crash at high speed when the cars fuse together as one and the momentum is still conserved but there is energy lost which is what makes it a Inelastic Collision.

  1. LD's Notes on Collisions from Unit A
  2. Animations are from google