Calculating Centripetal Acceleration of a 7200 RPM Hard Drive

[goracheski]

Homework Statement

The hard drives of many desktop computers spin at a maximum rate of 7200 rpm. If the diameter of the spinning disk in the harddrive is 3.51 cm, calculate the magnitude of the centripetal acceleration on the outside radius of the disk.

Homework Equations

a_c=v²/r

The Attempt at a Solution

r=0.01755 meters
but i don't know how to get the velocity from rpms

 

[tiny-tim]

hi goracheski!

… i don't know how to get the velocity from rpms

one revolution = one circumference …

how long is a circumference? ​