Friction<span> is the resistance to motion of one object moving relative to another. It is not a fundamental force, like gravity or electromagnetism. Instead, scientists believe it is the result of the electromagnetic attraction between charged particles in two touching surfaces.
Hope this is of great help to you, and happy studying~!
~Mistermistyeyed.</span>
I'm pretty sure it's Inertia and Gravity
Inertia deals with an object's tendency to stay in motion at a constant speed.
Hopefully this helped and good luck.
Answer:
Engular velocity: 
Linear velocity: 
The time it takes:

Explanation:
The magnitude of the centripetal acceleration can be related to the angular velocity and radius as:
(1)
Solving for w:
(2)
Replacing a=9,8m/s2 and r=6,375,000m:
(3)
And the angular velocity relates to the linear velocity:

The perimeter of the orbit is:

The time it takes:

Ok so the equation for momentum is:
v=p/m
So you would do:
7800/1200=6.5
So the answer is:
6.5 m/s
Hope this helps :)