# Calculating revolutions per minute

Sosa

## Homework Statement

A centrifuge is a device in which a small container of material is rotated at a high speed on a circular path. Such a device is used in medical laboratories, for instance, to cause the more dense red blood cells to settle through the less dense blood serum and collect at the bottom of the container. Suppose the centripetal acceleration of the sample is 4.60 x 10^3 times as large as the acceleration due to gravity. How many revolutions per minute is the sample making, if it is located at a radius of 4.59 cm from the axis of rotation?

## Homework Equations

ac=(4pi^2r) / T^2

## The Attempt at a Solution

rearranged the formula to get
T = sqrt (4pi^2r) / a
T = sqrt (4pi^2*0.0459) / 4.60 x 10^3 *9.8
T = 0.009358 *60 seconds
T = 0.561 rpm but it's wrong

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4.60 x 103 times as large
Or do you mean 103?
Where are your equations, and solution?

• Sosa
Sosa
Or do you mean 103?
Where are your equations, and solution?
updated it!

Is T supposed to be the time in seconds for one revolution?
Re-evaluate the applicability of the formula you are using.

mjc123