A computer hard disk starts from rest, then speeds up with an angular acceleration of 190 rad/s2 until it reaches its final angular speed of 7200 rpm. How many revolutions has the disk made 10.0 s after it starts up?

The number of revolutions that the disk made may be calculate by the equation,

2 x a x d = (Vf) ² - (V1) ²

where a is the acceleration. Vf and V1 are the final and initial velocities, respectively. Substituting the known values,

2 x (190 rad/s²) x (1 rev / 2π rad) x (60 sec / 1 min) ² x d = (7200 rpm) ² - 0

The value of d is approximately equal to 238.1 revolutions.