Finding revolutions per minute

[chenying]

Homework Statement

An astronaut is rotated in a centrifuge of radius 4.0 m.

Homework Equations

v = omega * radius

a = v^2/radius

The Attempt at a Solution

Ok, so I first found the omega for this acceleration, which came out to be

omega = 3.56179 s^-1

then I decided that since the it is revolutions per minute, I multiplied the vaule of omega by 60 seconds, and divided the value by the circumference of the circle.

(2*pi*4)/210.107 = .119619

So this answer is completely wrong because it does not make any sense whatsoever

 

[Kalvarin]

You need to know more data to work out the rpm, knowing just the radius of the centrifuge is not enough.

 

[chenying]

This was all that was given to me.

 

[Anden]

Omega = 2pi / Time, then you can get the time of one revolution

 

[Kalvarin]

Well rpm for a gven radius can infinetly many values. How did you work out the value of omega?

 

[chenying]

I used a = V^2/r since i have acceleration and r

Once I got the value of V, i substitute it into v = omega * radius and solved for omega.

 

[Anden]

You have forgotten to state the value of a in the question above.

 

[Kalvarin]

Oh ok, well then just use your value of omega in the formula anden gave you. That is the time for 1 revolution.

 

[chenying]

You have forgotten to state the value of a in the question above.

Sorry, the acceleration is 5g