question_answer

A pulley of radius 2 m is rotated about its axis by a force \[F=(20\,t-5{{t}^{2}})\] newton (where t is measured in seconds) applied tangentially. If the moment of inertia of the pulley about its axis of rotation is 10 kg \[{{m}^{2}}\], the number of rotations made by the pulley before its direction of motion if reversed is                                   [AIEEE 2011]

A) More than 9

B)   Less than 3

C)   More than 3 but less than 6

D)        More than 6 but less than 9

Correct Answer: C

Solution :

[c]

Also,