Centrifuge HW Problem

1. Sep 28, 2005

je55ica7

A sample of blood is placed in a centrifuge of radius 16.0 cm. The mass of a red blood cell is 3.0e-16 kg, and the magnitude of the force acting on it as it settles out of the plasma is 4.0e-11 N. At how many revolutions per second should the centrifuge be operated?

I can figure out the velocity... but the answer needs to be in revolutions per second. Would I just divide the velocity by the circumference of the centrifuge??

Last edited: Sep 28, 2005
2. Sep 28, 2005

Staff: Mentor

That's correct.

3. Sep 28, 2005

je55ica7

Ok, I figured out the problem using F=m(v^2/r). I got the right answer when I kept the mass in kg and solved for v. How could that be right if the answer had to be in rev/s? I don't get it...

4. Sep 28, 2005

Staff: Mentor

Calculate the circumference and you'll get it.

5. Sep 28, 2005

je55ica7

Lol

Soooo sneaky... hehe