# Homework Help: The Energy Method

1. May 8, 2007

### robip

1. The problem statement, all variables and given/known data
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

2. Relevant equations

0.5mv^2

3. The attempt at a solution

Not sure even where to start

2. May 9, 2007

### Staff: Mentor

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.

3. May 10, 2007

### robip

thanks I will give it a go and get back, im 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

4. May 11, 2007

### robip

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

5. May 11, 2007

### Staff: Mentor

Can you do it for a traditional pendulum?