# Proofing Moment of Inertia Solid Sphere

## Homework Statement

Can i use "pyramid" method to derive the equation of Moment Inertia solid sphere?
The pyramid is such we slice a watermelon.
Regards.

2/5 MR^2

## The Attempt at a Solution

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Hello chocophysuny,
Welcome to Physics Forums,

Can i use "pyramid" method to derive the equation of Moment Inertia solid sphere?

Have you tried it? You must show what you have tried to get help on PF (forum rules).

Sunil

haruspex
Homework Helper
Gold Member
It doesn't seem to me that it would be a useful approach. It does not simplify anything. You need to slice it into elements that have an easily calculated MI, such as discs perpendicular to the axis of rotation.

It doesn't seem to me that it would be a useful approach. It does not simplify anything. You need to slice it into elements that have an easily calculated MI, such as discs perpendicular to the axis of rotation.
But my lecture say this method is easy enough to solve.
And, actually i confused to find the element of volume and element of MI.

So, in your opinion, this is not solvable?

Hello chocophysuny,
Welcome to Physics Forums,

Have you tried it? You must show what you have tried to get help on PF (forum rules).

Sunil
Yes, I've tried it. But i didn't find the solution.
I'm confused with the element of volume and element of pyramid

"To find MI from the element, we need element of volume and element of MI, isn't it?"

"To find MI from the element, we need element of volume and element of MI, isn't it?"
I'm sorry, I didn't understand what you meant there.

haruspex