Moment of inertia?

Question

A rotating flywheel can be used as a method to store energy. If it is required that such a device be able to store up to a max of 1.00 x 10^6 J when rotating at 400 rad/sec, what moment of inertia is required?

Answer 1

The energy stored in a rotating system is 0.5*I*w^2, where I = moment of inertia, and w = angular velocity. So you would need a moment of inertial of

I = 2*E/w^2

Answer 2

if
W=400rad/sec
I =1.00*10^6
then moment of inertia is =1/2*I*W^2
=1/2*1.00*10^6*(400)^2
=8.00*10^10
this is the required moment of inertia.