How Do You Calculate Angular Acceleration and Mass in Physics Problems?

[skyhigh302]

Homework Statement

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?

Homework Equations

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!

 

[radou]

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

 

[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.

 

[radou]

Hint for 1:

Write down the expression for the acceleration (uniform!) of the car, and the expression for the angular displacement of the tire. The third expression you need is the connection between linear and angular acceleration.

 

[skyhigh302]

ooo ok thanks you so much!