A pulley of radius 2m is rotated about its axis by a force F = (20t – 5t 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 :
Text Solution
Verified by ExpertsThe correct answer is:
B
To reverse the direction 
(work done is zero)
τ = (20 t – 5t 2 ) 2 = 40t – 10t 2
α = 
ω = 
= 2t 2 – 
ω is zero at
2t 2 – 
= 0
t 3 = 6t 2 ⇒ t = 6 sec.
θ = 
= 
= 216 
= 36 rad.
No of revolution 
Less than 6
Prepare Smarter with CGP Edu
Get practice questions, solutions, and test series in one place.
Write a Review
Share your experience with this question and solution.
Commentary
Send your comment, doubt, correction, or feedback to admin.
Similar Questions
Explore conceptually related problems
Three blocks A, B and C are lying on a smooth horizontal surface, as shown in the figure. A and B h…
A piece of wood of mass 0.03 kg is dropped from the top of a 100 m height building. At the same tim…
A simple pendulum, made of a string of length λ and a bob of mass m, is released from a small angle…
The position vector of the centre of mass cm of an asymmetric uniform bar of negligible area of cr…
Three point particles of masses 1.0 kg, 1.5 kg and 2.5 kg are placed at three corners of a right an…
As shown in figure. When a spherical cavity (centred at O) of radius 1 is cut out of a uniform sphe…