# A billiard ball of mass .155 kg moves with a velocity of 12.5 m/s toward a stationary billiard ball of identical mass and strikes it in a head on collision. The first billiard ball comes to a complete stop. Was the collision elastic?

##### 1 Answer

Mar 18, 2018

Suppose,a ball of mass

Let,after the collision velocity of the 2nd mass will be

So,applying law of conservation of momentum,

so,

so,kinetic energy before the collision =

and after the collision,kinetic energy became =

So,kinetic energy before and after the collision remains the same.

Hence it was an elastic collsion.

Remember,in an elastic collsion,two identical mass just exchange their velocity.

And,coefficient of restitution is