Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R
Assertion A : An electric fan continues to rotate for some time after the current is switched off.
Reason R : Fan continues to rotate due to inertia of motion.
In the light of above statements, choose the most appropriate answer from the options given below.

Solution

Physics sir · 4 steps

Switching off removes the push, not the motion: the blades keep spinning until friction stops them.

1. Check A. When the switch is turned off, the motor stops supplying torque. Yet the blades do not stop at once; they slow down over several seconds. So A is correct.
2. Check R. Inertia of motion is the tendency of a body to keep moving as it is moving. For a rotating body this means it keeps rotating unless an external torque changes it. So R is correct.
3. Link them. After the current is cut, the only torques left come from friction at the bearings and air drag on the blades. These are small, so the blades keep turning because of their inertia of motion and slow down only gradually. That is exactly what R says, so R explains A.
4. So. Both statements are true and R is the correct explanation of A, which is option (c).

The idea to keep. A force or torque is needed to change motion, not to keep it going. When the drive is removed, a body keeps moving by inertia and is stopped only by friction.

Answer from the NTA final answer key. Solution by PrepWiser.