The angular momentum of a body changes by 80kg `m^(2)s^(-1)` when its angular velocity changes from 20 rad `s^(-1)` to 40 rad `s^(-1)`. Find the change in its kinetic energy of rotation.

Explanation

Change in angular momentum of the body
`L_(2)-L_(1)=I(omega_(2)-omega_(1))`
Change in kinetic energy `=(1)/(2)l(omega_(2)^(2)-omega_(1)^(2))`
`("change in K.E")/("change in angular momentum")=(omega_(2)+omega_(1))/(2)`
`:.` change in K.E. `=80((20+40)/(2))=2400J`