Momentum: Is collision between 2 equal massed billard balls elastic or inelastic?

Question

first ball is at rest and second ball is shoot towards the first ball. After collision one ball rolls to one side at an angle and other to other side at an angle, forming a Y. Balls are of equal mass. Is collision between 2 billard balls elastic or inelastic.
(please only try to post if100% sure)

Answer 1

It is elastic. I can explain it to you, and I guarantee someone can explain it better but a picture speaks 1000 words.

http://en.wikipedia.org/wiki/Elastic_collision
Scroll halfway down.

Answer 2

100% sure that the collision is elastic.

In an elastic collision, the colliding objects do not stick together which of course the billard balls do not.

This collision, on a real billard table in real life is not "perfectly elastic" because KE is not conserved. In fact some of the kenetic energy of the second ball (the one that was shot at the first) is actually transferred to sound energy (the crack) of the collision. Momemtum however is conserved. An elastic collision. 100% Certain.

Answer 3

The easiest way to remember the difference between elastic and inelastic collisions is that there are two states of deformation: elastic, where it returns to its original shape, and plastic, where it is permanently deformed. An example of elastic deformation is when a spring is stretched and allowed to return to its original length, plastic deformation occurs when you stretch the spring too far and it stays that way. Inelastic and plastic mean pretty much the same thing. The object does not spring back to the way it was. The billiard balls deform slightly on impact, but not much and spring back to round. From the approach velocity and direction you can calculate the separate velocities and directions after impact. If they were two soft lead balls, there would be plastic deformation consuming energy. The final velocities would be lower and the directions couldn't be predicted as well. That would be more of an inelastic collision. Pure elastic and pure inelastic are ideals, of course.

Answer 4

If the balls go their separate ways after the collision, and the total kinetic energy after collision is the same as before, then this is a fully elastic collision. If the balls stick together and move as one after the collision, the collision is inelastic. Momentum in both cases is conserved.