The motor of an engine is rotating about its axis with an angular velocity of 100 rev/minute. It comes to rest in 15 s, after being switched off. Assuming constant angular deceleration, calculate the number of revolutions made by it before coming to rest.

Explanation

The initila ngular velocity =100 rev/minute =(10pi/)rad/s`
FiN/Al angular velocity =0
Time interval =15s ltbr. Let angular acceleration be `alpha`. Using the equation `omega=omega_0+alphtat` we obtain alpha=(-2pi/9) rad/s^2`
The angle rotated by teh motor during this motion is
`theta=omega_0t+1/2alphat^2`
`=((10pi)/3 (rad)/s) (15s) -1/2 ((2pi)/9 (rad)/s)(15s)^2`
Hence the motor rotates thrugh 12.5 revolutions before coming to rest.