Question

A wheel is rotating about an axis through its centre at 720rpm. It is acted on by a constant torque opposing it's motion for 8 seconds to bring to rest finally. The value of torque in nm is

Answer 1

Torque = moment of inertia of the wheel X acceleration

         T = Iα-------- (1)

now we can get acceleration by using rotational motion equation,

starting velocity=ω1= 720 rpm = (720 X 2π)/60 =24π rad/s

ending velocity = ω2 = 0

time =t = 8s

ω2 = ω1 + αt

0 = 24π + 8α

α = -3π---------- (2)

But, moment of inertia of a wheel = I = MR² (M = mass of the wheel,

                                                                         R = radius of the wheel)

Then we can substitute I & α into the equation 01,

T = MR² X (-3π) = -3πMR²

Answer 2

Explanation:

above photo gives you a correct answer this answer from jee mains level exam