# Homework Help: Kinetic energy dissipation

1. Nov 5, 2008

### tater08

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

A hockey puck B rests on a smooth surface of ice and is struck by a second puck A , which was originally traveling at 40.0 m/s and which is deflected 30.0 degrees from its original direction. Puck B acquires a velocity at a 45.0 degree angle to the original direction of A . The pucks have the same mass.

what fraction of the orignal kinetic energy of puck A dissipates during the collision.

2. Relevant equations
(Delta K) /K
KE=0.5 mv^2

3. The attempt at a solution
i was able to solve for the velocity of both block a and b. But now i can't seem to figure out the original kinetic energy. I do not know where to go with the masses being the same.
Va=29.3 m/s
Vb=20.7

2. Nov 5, 2008

### Redbelly98

Staff Emeritus
You can express the kinetic energy in terms of the unknown mass "m", and go from there.

3. Nov 5, 2008

### tater08

(Kei-Kef)/ KEi = ((1-(m1/m1+m)) KEi)/KEI = M2/m1+M2 1/ (1+1) KE should be 0.5 or 50 percent. But this is the wrong answer And I'm Totally lost. thanks for any help that i may receive.

4. Nov 6, 2008

### tater08

I figured it out. 1-(KEf-KEi)/KEI is basically the equation to use.