Posted by sanjeev kumar on .
a flywheel has an angular speed of 1200rev/min when its motor is turned off.the wheel attains constant decelerations of 1.5rad/s2 due to friction in its bearing.determine the time required for the wheel to come to rest and the numer of revolutions the wheel makes before it comes to rest.

Dynamics 
Ajayb,
Wi= 1200 rev/min = 20 rev/sec
= 20*2*pi rad/sec
Wf = 0; alpha= 1.5 rad/s^2
Wf = Wi + alpha*t
0 = 40*pi  1.5*t
t = 40*pi/1.5 = 84 sec
Now,
theta = Wi*t + (1/2)*alpha*t^2
Plug in the values in this eqn. to get theta  the rotation of the wheel (in radians)before it comes to halt. Divide the result by 2*pi to convert into no. of revolutions. 
Dynamics 
Rajan,
Please help me to elaborate the answer as i tried but couldn't