An ice skater having moment of inertia `l` rotating with angular speed `omega` suddenly opens her arms, which reduces her angular velocity to `(omega)/(4)`. Calculate the change in moment of inertia of the dancer.

Explanation

`L = l omega`
as `tau = 0, L =` constant
`l omega = l' omega'`
`l'=(l omega)/(omega'),l'=(4l omega)/(omega)=4l`
Change in moment of inertia `= l'-l = 3l`
Hint : Find new moment of inertia l', then change `= l'-l`