What is the speed of the 8-ball after the collision?

[Whitestripes]

1. 
   In a pool game, the cue ball, which has an initial speed of 1.3 m/s, makes an elastic collision with the 8-ball, which is initially at rest. After the collision, the 8-ball moves at an angle theta = 33.2o with respect to the original direction of the cue ball, as shown in the figure. Assume the pool table is frictionless and the masses of the cue ball and the 8-ball are equal. What is the speed of the 8-ball after the collision?
   
   
   

2. Mgh + W = 1/2mv^2
p=mv3. I was easily able to get that phi was 56.8 deg because of the 90 deg angle. Now I am lost at how to find the velocity of the 8 ball without the velocity of the cue ball?

 

[BvU]

Hello White and welcome to PF :-)

Your collection of relevant equations needs revision and extension. Mgh and W are unlikely to play a role in this drama...

 

[HallsofIvy]

Conservation of momentum and energy are most important. But "Mgh" is irrelevant here. It is the potential energy of a mass M at height h, but there is no "height" here.