A flywheel of moment of inertia 5.0 kg m^2 is rotated at a speed of 60 rad/s. Because of the friction at the axle, it comes to rest in 5.0 minutes. Find a. The average torque of the friction. B. the total work done by the friction and c. the angular momentum of the wheel 1 minute before it stops rotating.

Answer

A, B, C

Explanation

A fly wheel of moment of inertia 5 kg m is rotated at a speed of 60 rad/s. The fly wheel comes to rest due to the friction at the axis after 5 minutes.
therefore the angular deceleration poroduced due to friction force
`omega=omega_0+at`

`rarr omega_0=-at`
`rarr a=-(60/5xx60)`
`=-1/5rad/s^2`
a. therefore total work done in stopping the wheel by frictioN/Al force
`W=1/2 Iomega^2
`=1/2xx5xx(60xx60)`
`=1N-mopposite to the rotation of wheel
c. Angular velocity after 4 minutes
`rarr omega=omega_0+at`
`=60-240/5`
`60/5=12rad/s`
Therefore angular mometum abut the centre
`=Ixxomega`
`=5xx12=60kg-m^2/s`