Kinetic Energy of Hemi-sphere: The Energy Method

[robip]

Homework Statement

A solid hemi-sphere of radius r rests on a hard flat surface. If rolled slightly in 1 direction and released, the hemisphere will rock from side to side, assume no slipping. Write an expression for the kinetic energy of the hemi-sphere during the small amplitude motion

Homework Equations

0.5mv^2

The Attempt at a Solution

Not sure even where to start

 

[berkeman]

Start by figuring out how the center of mass of the hemisphere is raised when it is tilted to some angle theta. That raising of the CM is what provides the energy to make the motion happen.

 

[robip]

thanks I will give it a go and get back, I am assuming that the center of mass would be through the axii of symetry and 3/8th's the radius i.e x0,y0,z3r/8

 

[robip]

ok i am completely stuck, i have no idea how to work this out

 

[berkeman]

Can you do it for a traditional pendulum?