# I NEED HELP ! Rotational and Momentum problem

1. Dec 14, 2006

### skyhigh302

1. The problem statement, all variables and given/known data
I have two problems...

1. The tires of a car make 65 revolutions as the car reduces its speed uniformly from 10.8 m/s to 4.25 m/s. The tires have a diameter of 0.80 m. What was the angular acceleration of the tires in rad/s2?

2. A 0.301-kg croquet ball makes an elastic head-on collision with a second ball initially at rest. The second ball moves off with half the original speed of the first ball. What is the mass of the second ball?

2. Relevant equations

3. The attempt at a solution

Basically, I don't know where to start at. For both problems, i've tried everything and it won't work. SOME PLEEEEEEEEEAAAASE HELP!

2. Dec 14, 2006

Well, what exactly is this 'everything' you've tried for both problems? Among this 'everything' there should be some relevant equations, right?

3. Dec 14, 2006

### skyhigh302

well for number 1, I tried finding the velocity but I couldn't. If I can find the velocity, I can find everything else.

For number 2, I figured you would use the m1v1=m2v2 equation but that doesn't work.

4. Dec 14, 2006