How Do You Calculate the Constant Angular Acceleration of a Centrifuge?

[perfectlovehe]

A centrifuge in a medical laboratory rotates at an angular speed of 3500 rpm (revolutions per minute). When switched off, it rotates 70.0 times before coming to rest. Find the constant angular acceleration of the centrifuge. (Assume the initial direction of rotation is the positive direction. Indicate the direction with the sign of your answer.)

 

[JaredJames]

Please use the correct formatting and show your attempt at this question as per PF guidelines.

Jared