# Homework Help: Rotational Kinematics of a Computer Disk

1. Nov 5, 2007

### Superfluous

A computer disk drive is turned on starting from rest and has constant angular acceleration.

If it took 0.410 s for the drive to make its second complete revolution, how long did it take to make the first complete revolution? What is its angular acceleration, in rad/s^2

I cannot find out how to determine the time it takes to complete the first revolution or the angular acceleration at all. Every rotational kinematics equation involves angular velocity, which is not given (except for the fact that it starts from rest).

I do not know how to go about this or which of the exact kinematic equations to use. Any help would be appreciated.

2. Nov 5, 2007

### Superfluous

I've spent several hours on this plugging in and manipulating the rotational kinematics equations but I still cannot figure out what to do. I'm sure it's something extremely obvious, but I can't seem to figure it out. So... any hint at all would be nice. Thanks.

3. Nov 5, 2007

### hotcommodity

Work on finding the angular acceleration first. We know that the angular acceleration is constant, so we can use the equations for rotational kinematics. You'll probably want to use $$\theta = \omega_0 t + .5 \alpha t^2$$.