# Physic problem

1. Dec 9, 2006

### blackout85

If a wheel is turning at 3.0 rads/s, the time it takes to complete one revolution is about:

now do I just times by 60s to cancel the seconds out to get 1 revolution.

The rotational speed of the minute hand of a watch is:

w= anglular displacement/ time
w=2pi radian in a circle/ 3600 seconds in one rotation --> pi/1800 rad/s
is that right?

2. Dec 9, 2006

### marcusl

No, that would give the number of revolutions in 60 seconds. How do you think you can get an answer in seconds/revolution?

How many seconds in a minute?

3. Dec 9, 2006

### blackout85

For the first problem I just want the answer in seconds, not seconds/revolutions

I put 3600 seconds because it is the amount of time for the minute hand to make one full revolution around the clock

4. Dec 10, 2006

### marcusl

Understood. If the wheel makes 0.477 revolutions in 1 second, then the time it takes to make 1 rev is 1/0.477 = 2.094 seconds. You need to take the inverse of the speed (that gives sec/rev) and multiply by the number of revolutions (in this case 1).