Question

A white billiard ball with mass mw = 1.32 kg is moving directly to the right with a speed of v = 2.91 m/s and collides elastically with a black billiard ball with the same mass mb = 1.32 kg that is initially at rest. The two collide elastically and the white ball ends up moving at an angle above the horizontal of ¦Èw = 20¡ã and the black ball ends up moving at an angle below the horizontal of ¦Èb = 70¡ã.

Answer 1

You will have to solve this in two directions of momentum.

let the intial direction be x.
You know the intial momentum, and masses, and let the final be vwhite'x and vblack'x


the initial momentum in the y directtion is zero, so the sum of the final y momentums is zero, which leads to
vwhite'y=-vblack'y

With those two equations, and the angles, you can solve for the final velocities

Answer 2

A cue ball rolling across a pool table at 5.7 m/s collides with a stationary eight ball of equal mass. The cue ball stops after the collision. What is the velocity of the eight ball after the collision?