Question

Would you imagine that the moment of inertia of the earth around its own axis is a negligible fraction of its moment of inertia about the axis of rotation around the sun. Support your explanation with substantial data.

Answer 1

Answer:

Well, let’s put our math where our mouth is.

Moment of inertia of a sphere around its center:

I=mr2/5

I=6.0x1024kg∗(6.3x106m)2/5

I=3.0x109kg/m2

2. Moment of inertia of a point around a center:

I=mr2

I=6.0x1024kg∗(1.5x1011m)2

I=1.35x1050kg/m2

So, yes, it’s a bit larger.

Larger by 41 orders of magnitude or roughly 50.000.000.000.000.000.000.000.000.000.000.000.000.000 times larger, so I imagine this classifies as “negligible”.