# Homework Help: Circular Motion

1. Feb 21, 2006

### rachael

An object of mass 4.0 kg is whirled in a horizontal circle
of radius 0.40 m with a constant speed. If the tension in
the wire is 80 N, a=20 m/s, v= 2.83m/s, T= 0.89 s find:
d the number of revolutions made every minute.

2. Feb 21, 2006

### cepheid

Staff Emeritus
3. Feb 21, 2006

### phucnv87

With the datum about $$T$$ you gave, I think there's no need for other data to find the revolutions per minute.

4. Feb 21, 2006

### rachael

yes i have attemted the questions from part a,b,c
but i can't figure what formulae to use to find the number of revolution

5. Feb 21, 2006

### cepheid

Staff Emeritus
k, but did you read what phuncv87, or whatever...:p said?

You have the period? What is that? The period of time required for one full revolution to occur. If you know that, can you tell me how often a revolution occurs in one second? What is that? The frequency. Yeah you can, because you know the amount of time needed for one revolution (period), and that's a simple relationship. Give it a shot and let us know how it goes.

6. Feb 21, 2006

### rachael

oh i c, you use T=1/f then times it by 60secs