Roger,
Yes you are right in princable but we are dealing with rotating mass not mass traveling in a straight line!
There are questions involving moments of inertia to contend with as well as angular velocity.
I also confess to be a bit rusty but as I remember it the kinetic energy of a rotating mass is somthing like..


Kinetic energy = ½ moment of inertia X angular velocity squared

or E = 1/2Iw^2


I hope this helps, although as I said its been a long time since I really had a use for maths like that so dont take it as gospel!

Geoff,
Team Scorpion.