A particular planet has a moment of inertia of 9.74 × 1037 kg•m2 and a mass of 5.98 × 1024 kg. Based on these values, what is the planet’s radius?

Question

matt101 · Answer

You can approximate the planet as a solid sphere with uniform density. That means the equation for moment of inertia you should be using is the following:

$$I=\frac{2}{5}MR^2$$
Solve for R and you have your answer!

kiakat · Answer

What is the 2/5ths?

irishboy123 · Answer

kia go down to sphere... https://en.wikipedia.org/wiki/List_of_moments_of_inertia

matt101 · Answer

It's just a dimensionless coefficient you multiply by. It's there because of how the equation for moment of inertia is calculated in the first place which you may not need to know (that's explained in the link provided above).