Question

An optical disk drive in your computer can spin a disk up to 10,000 rpm (about 1045 rad/s). If a particular disk is spun at 470.2 rad/s while it is being read, and then is allowed to come to rest over 0.167 seconds , what is the magnitude of the average angular acceleration of the disk? average angular acceleration: rads2 If the disk is 0.12 m in diameter, what is the magnitude of the tangential acceleration of a point 1/5 of the way out from the center of the disk? tangential acceleration:

Answer 1

From the angular kinematics, we get
  

now given w_2 = 0, w_1 = 470.2 rad/s, t = 0.167 s, so,
  
The negative sign implies that the disk is actually deccelerating.
So, the magnitude of the angular acceleration is
  
And the magnitude of the tangential acceleration is