# Mechanics problem help

1. Jan 30, 2006

### Amith2006

Sir,
1) Consider two spherical balls one made of wood and other made of iron having the same diametre. Which one has greater moment of inertia about their centre of gravity?

2. Jan 30, 2006

### Triss

The formula for any solid sphere is
$$I=\frac{2}{5}mr^2$$

3. Jan 30, 2006

### Amith2006

Sir,
My doubt is - For a given radius, the iron sphere having a greater mass should have larger moment of inertia, isn't it?Suppose mass of iron sphere is twice the mass of wooden sphere. In that case,
Moment of inertia of wooden ball = 2/5(MR^2)
Moment of inertia of iron ball = 2/5(2MR^2)
Here the symbol "^" represents power.

4. Jan 30, 2006