Question

A cooling fan is turned off when it is running at 900rev/min . It turns 1100 revolutions before it comes to a stop.

Part B How long did it take the fan to come to a complete stop?

Answer 1

1 revolution = 2 radians

1 minute = 60 seconds

Initial angular speed of the cooling fan = 1 = 900 rev/min = 900 x (2/60) rad/s = 94.25 rad/s

Final angular speed of the cooling fan = 2 = 0 rad/s (Comes to a stop)

Number of revolutions made by the cooling fan before coming to rest = n = 1100 rev

Angle through which the cooling fan rotates before coming to rest =

= 6911.5 rad

Angular acceleration of the fan =

Negative as it is deceleration.

Time taken by the fan to come to a stop = T

T = 146.6 sec

Time taken by the fan to come to a stop = 146.6 sec