If the frictional torque is constant, the fan will slow down linearly from its original rotational speed of 90 rpm, equivalent to 1.5 rev/s. Linear slowdown implies that the average rotational speed until a complete stop is half of the top speed. Therefore the fan rotates at an average of 0.75 rotations per second. The time t to stop is therefore:
Mass and distance force /pull of gravity decreases with the increase in separation between the two bodies the amount of gravity an object possesses is proportional to the mass of that object.
