Answer:
For outer points of shell

Now for inner point of shell

Explanation:
As we know that out side the shell electric potential is given as

inside the shell the electric potential is given as

now we know the relation between electric potential and electric field as

so we can say for outer points of the shell



Now for inner point again we can use the same



Answer: Moon is much smaller in size and has very less mass, when compared to our mighty earth and there is absence of strong magnetic field on the moon which could protect from the incoming solar radiation from the sun. Since there is no magnetic field, it can swipe off any materials that are present there on the moon, diminishing the atmosphere.
This is the reason why moon does not have any atmosphere.
The force decreases due to less frictional resistance. it becomes easier to keep it moving as it is already moving, one of the Newton's laws