# Calculate Moment of Inertia - Stick and Ball

1. Nov 27, 2009

### vm310

1. The problem statement, all variables and given/known data
What is the moment of inertia about the y-axis for the system as shown. The stick has a length of 2L and a mass of M. The solid sphere has a diameter of L and a mass of 2M.

2. Relevant equations

I=$$\int$$r2dm
$$\lambda=\frac{m}{l}$$

3. The attempt at a solution
Should I have to integrals for this one? one for the stick and one for the sphere? Please help.

2. Nov 27, 2009

### Staff: Mentor

No need to do any integration, just use standard formulas for the moment of inertia of a stick and a sphere. Hint: Parallel axis theorem.

3. Nov 27, 2009

### pgardn

What does your teacher want? Do they want you to solve this using integration? This would take a bit of time for these two bodies. Or have you already been given the moment of inertia of a rod and a sphere and all you really need is the parallel axis theorem?

I guess what I am asking is this an assignment meant for practicing integration using the ideas of linear density and such, or just merely to find the moment of inertia for these bodies?

Doc Al and I must be in some sort of resonance. Sorry again.

Last edited: Nov 27, 2009