# Homework Help: Energy Loss

1. Oct 10, 2009

### CaptFormal

1. The problem statement, all variables and given/known data

One hockey puck of mass 0.2 kg strikes an identical stationary puck on a frictionless ice rink. If the first puck had a velocity V0 = 3.8 m/s before the collision and V1 = 1 m/s after in the same direction, what fraction of the energy was lost?

2. Relevant equations

M1V1 + M2V2 = M1V1' + M2V2'

3. The attempt at a solution

So, I think I am supposed to use the above equation but I am not completely sure. Also, I am a bit confused as to the question "what fraction of energy was lost". Not sure what to do as my efforts in trying to use the above equation has failed. Any assistance or suggestions are greatly appreciated. Thanks.

2. Oct 10, 2009

### Donaldos

What kind of energy are we talking about here?

3. Oct 10, 2009

### CaptFormal

I don't know. This homework revolves around linear momentum but that is about all the information that I have. In the past we did go over potential and kinetic energy. Not sure if that helps or not.

4. Oct 10, 2009

### Donaldos

Does the potential energy of the first pluck vary?

5. Oct 10, 2009

### RoyalCat

I'm afraid that's completely unrelated, Donaldos.

CaptFormal, you have half of your answer in your hands. Use the conservation of momentum to find the velocity of the second puck after the impact.

After that, look at the total energy before the collision, and the total energy after the collision.

Hint:
There is only kinetic energy before the collision, but some of the energy is lost to heat during the collision.

6. Oct 10, 2009

### Donaldos

And I'm afraid it's directly related to CaptFormal's previous reply...