(a) calculate the magnitude of the angular momentum of the earth in a circular orbit around the sun. is it reasonable to model it as a particle? (b) calculate the magnitude of the angular momentum of the earth due to its rotation around an axis through the north and south poles, modeling it as a uniform sphere. consult appendix e and the astronomical data in appendix f.

(a)

(b)

Explanation:

For Earth we have:

(a)

Angular momentum,

∵...............................(1)

For a particle of mass m moving in a circular path at a distance r from the axis,

&

Putting respecstive values in eq. (1)

To model earth as a particle is  reasonable because the distance between the sun and the earth is very large s compared to the radius if the earth.

(b)

For a uniform sphere of mass M and radius R and an axis through its center,  

using eq. (1)

electric field is a function of 1/r^2

yes, the force per unit charge for a point charge is inverse square law.