7.3 - Physics Help! Acceleration!?

Question

The crankshaft in a race car goes from rest to 3000 rpm in 2.9 seconds.

Part A

What is the crankshaft's angular acceleration? Express in rad/sec^2

Part B

How many revolutions does it make while reaching 3000 rpm?

Answer 1

Part A

3000 rpm = 50 rev/s = 100pi rad/s

acceleration = 100pi/2.9 rad/sec^2 = 108.3 rad/sec^2

Part B

rotations = 1/2 (angular acceleration) t^2

= 0.5 * 108.3 * 2.9^2 = 455.5 rad = 455.5/(2pi)

= 72.5 revolutions.