Question

A thin walled shell of mass 1.5 kg and radius 0.2 m is rotating with an angular speed of 24 rad/s. An external retarding torque of 0.12 Nm starts acting on it. How long (in sec) does it take for it to come to rest?​

Answer 1

Answer:

Correct option is A)

Let the final angular velocity be w.

Applying conservation of angular momentum : L

f

=L

i

Or (

2

M

disc

R

2

w)+M

particle

R

2

w=(

2

M

disc

R

2

)w

i

+0

Or

2

2×0.2

2

×w+0.25×0.2

2

×w=(

2

2×0.2

2

)×30

⟹ w=24 rad/s