A ballet dancer spins about a vertical axis at 60 rpm with arms outstretched. When her arms folded the angular frequency increases to 90 rpm. Find the change in her moment of inertia.

A ballet dancer spins about a vertical axis at 60 rpm with arms outstr

1.	A ballet dancer spins about a vertical axis at 60 rpm with arms outstretched. When her arms folded the angular frequency increases to 90 rpm. Find the change in her moment of inertia.
Answer» Solution :By the principle of conservation of angualr momentum `Ixx60=I_(2)xx90` FINAL moment of INERTIA, `I_(2)=(2I)/(3)` Change in moment of inertia `=I-(2I)/(3)=(I)/(3)` Assuming the initial I to be 100% change in moment of inertia `=(100)/(3)%=33(1)/(3)%`.