# Rolling coin

1. Oct 27, 2006

### starfish794

If a coin with a radius of 2.2cm rolls for 9.034s, how far does it roll?

The answer needs to be in meters so 2.2cm=.022m. Is there a simple formula for this? I feel like I'm missing something easy.

2. Oct 27, 2006

### OlderDan

Something is missing. You need to know the speed of the coin to answer this question.

3. Oct 27, 2006

### starfish794

A coin with a diameter of 2.20 cm is dropped on edge onto a horizontal surface. The coin starts out with an initial angular speed of 15.9 rad/s and rolls in a straight line without slipping. If the rotation slows with an angular acceleration of magnitude 1.76 rad/s2, how far does the coin roll before coming to rest?

That was the original question and then i used w=w+(alpha)t to find the time.

4. Oct 27, 2006

### OlderDan

Use the other equations of rotational kinematics (w=w+(alpha)t is just one of this set of equations) to find the angular displacement of the coin during this time interval. Then figure out how far a point on the circumference of the coin would have moved if the coin had just been rotating about its center. Since the coin was not slipping, this is the distance the coin moved before coming to a stop. In one rotation, the coin moves one circumference.