# Homework Help: Calculate rpm with circular motion

1. Oct 22, 2012

### Workout

1. The problem statement, all variables and given/known data
Imagine that NASA plans to builds a large donut-shaped space station. The station will rotate in outer space in order to simulate gravity. If the station has a radius of 200m, what must be its rotation speed in revolutions per minute, to produce an artificial gravity of 0.8 g?

2. Relevant equations
ac=v^2/r
rev/min = 60v/2pi*r

3. The attempt at a solution
Okay, so I have somewhere in my notes that if ac = g then T = 0. So I replaced ac with 0.8. So my equation went 0.8 = v^2/(200m).

So I got my v = 12.65 m/s.

Then I plugged my v into rev/min at 60(v)/2pi*r and I got my answer to be 0.604 rev/min.

I was just wondering if I did this right?

2. Oct 22, 2012

### Simon Bridge

3. Oct 23, 2012

### Workout

How do I solve for rpm? I think my v is correct.

4. Oct 25, 2012

### Simon Bridge

Well, since you are sure you have the correct v...
You can either convert your v into angular velocity or work out the circumference of your circle and how many times you'd travel that distance at speed v in one minute.