# Rolling Question

1. May 12, 2009

### Lord Dark

1. The problem statement, all variables and given/known data
Hi again ,, my second one is easy:

A tire 0.5 m in radius rotates at a constant rate of 200 rev/min. Find the speed and
acceleration of a small stone stuck on the surface of the tire (on its outer edge).

2. Relevant equations

3. The attempt at a solution
the Speed of the rock is easy to get (W=200 rev/min = (20*pi)/3 rad/s = (10*pi)/3 m/s)
about the acceleration : should I get the tangent acceleration or the radial ??

Last edited: May 12, 2009
2. May 12, 2009

### rock.freak667

Constant angular velocity means that the angular acceleration is zero. So the tangential acceleration is zero.

3. May 12, 2009

### Lord Dark

so the question means i should get the tangent acceleration right not the radial one ?

4. May 12, 2009

### rock.freak667

$$a_t = \alpha r$$

$$a_r = \frac{v^2}{r}$$

seeing as that $\alpha=0$, which one do you think you should find?

5. May 13, 2009

### Lord Dark

lol ,, got it :) ,, thanks ,, exam questions are so poor -_-