Question

Some dragonflies splash down onto the surface of a lake to clean themselves. After this dunking, the dragonflies gain altitude, and then spin rapidly at about 1100 rpm to spray the water off their bodies. When the dragonflies do this "spin-dry," they tuck themselves into a "ball" with a moment of inertia of 2.1×10−7kg⋅m2.

How much energy must the dragonfly generate to spin itself at this rate?

Answer 1

KE in the rotation= 1/2 *momnet*w^2
moment is given
w=2PI*1100/60 rad/sec

solve for KE