Energy loss fraction when a hockey puck hits another at rest

[CaptFormal]

Homework Statement

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?

Homework Equations

M1V1 + M2V2 = M1V1' + M2V2'

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.

 

[Donaldos]

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?

What kind of energy are we talking about here?

 

[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.

 

[Donaldos]

Does the potential energy of the first pluck vary?

 

[RoyalCat]

Does the potential energy of the first pluck vary?

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:

Spoiler

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

 

[Donaldos]

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

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