# Relative difference between moment of inertia for the earth

1. May 3, 2014

### zeralda21

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

The earth is slightly thicker around the equator and hence $I_{0}\neq I_{\zeta}$ I am curious in finding the angular velocity for the **precession** between using the fact that the distance between the spin axis and the precession axis is 10 meters on the surface of earth.

The moment of inertia can be found here:

http://scienceworld.wolfram.com/physics/MomentofInertiaEarth.html

3. The attempt at a solution

I know that the precession velocity $\dot{\psi}=\frac{Iv}{(I-I_{0})\cos\theta}$, where $v$ is the spin velocity and can we found using $2\pi/T$,where $T$ is period time in seconds. I'm not sure about the magnitude of $\theta$ and if I can neglect it.

2. May 4, 2014

### paisiello2

What is the precession axis?

What is theta supposed to be?

3. May 4, 2014

### zeralda21

Theta is the angle between the spin axis and precession axis. Precession axis is the axis which the earth precess about.

4. May 5, 2014

### paisiello2

Isn't theta then equal to the tilt of the earth's axis = 23.5 degrees?

How did you come up with 10m? And where did you get your formula?