# Gravitational energy

1. Jul 15, 2011

### Bravodhan

When I multiplied angular accelaration with surface area of sphere .I got an equation for energy.

What do this equation mean by?
Is this equation describe gravitational energy?

2. Jul 16, 2011

### Drakkith

Staff Emeritus
Can you post the equations you used and the problem they were used in?

3. Jul 16, 2011

### Bravodhan

But dimensionally this equation is correct.

4. Jul 16, 2011

### Bravodhan

Angular accelaration*surface area of a sphere = Energy
Angular velocity/time*4(pi)r2=Energy

Dimensional formula:-
M0 L0 T-2 * M L2 T0 = M L2 T-2

M L2 T-2 = Energy

I take this energy equation in terms of planetry motion .

Last edited: Jul 16, 2011
5. Jul 16, 2011

Staff Emeritus
The fact that something has dimensions of energy doesn't make it an energy. Torque, for example.

6. Jul 16, 2011

### jimgraber

First, if its truly surface area, you get M0 not M. The whole equation is massless.
The way you have written it, it is the mass of a thin spherical shell times the angular acceleration.

Second, Work also has the dimensions of Energy. I think your equation gives you the amount of work expended to accelerate (spin up or spin down) the thin spherical shell by that much.
Best,
Jim Graber