# Homework Help: Elastic Collision of Ball and Block

1. Oct 13, 2009

### munchy35

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

A steel ball of mass .500 kg is fastened to a cord that is .70 m long and fixed at the far end. The ball is then released when the cord is horizontal. At the bottom of the path, the ball strikes a 2.50 kg steel block initially at rest on a frictionless surface. The collision is elastic.

The first part was to find the speed of the ball and block after the collision.

The ball was -2.47 m/s

and

The block was 1.23 m/s

I'm having trouble finding the height the ball will rise after collision in terms of the angle to the vertical

2. Relevant equations

I used v1f = (m1 - m2 / m1 + m2) * v1i for the speed of the ball

and

v2f = (2mi/m1+m2) v1i for the speed of the block

for the angle of the height of the ball...

i'm guessing i might need to use a vector equation...tan-1 x = (ry/rx)

3. The attempt at a solution

I already received the solution for the first part.

For the height,

I guess since v1= -2.47 m/s.... don't know how to relate...

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