Question

A wheel of mass 120 kg and radius of gyration of 1 metre is rotating with a speed of 3000 RPM.A retarding torque is applied on the wheel so that it come to be rest in 5 sec. What is the mantra of returning torque? ​

Answer 1

Explanation:

A wheel of moment of inertia 1kgm

2

is rotating at a speed of 40rad/s. Due to friction on the axis, the wheel comes to rest in 10 minutes. Calculate the angular momentum of the wheel, two minutes before it comes to rest.

Medium

Answer 2

Given : I=1kgm2

             ω1=40rad/s,   ω2=0 at

              t=10 minutes =60×10s=600s

              t′=8 minutes =60×8s=480s

              ω2=ω1+αt

              α=tω2−ω1

                  =6000−40=−151rad/s2

At time t′          ω3=ω1+αt′

                           =40−151×480

                           =40−32=8rad/s

∴          L=Iω3

              =I×8=8kgm2/s