Answer:
d. The magnitude of the work done by the earth on the satellite is non zero
Explanation:
The work done is equal to the product of the force and the distance moved in the direction of the force, the force and the distance act perpendicular to one another, therefore no work is done in the circular motion of the movement of the earth.
If there is no friction, the roller coaster would keep moving forever but a constant velocity. The only way it would accelerate is if there was a force continually pushing on it.
PE = (250) (30) (9.81) = 73575J
I used to use 9.81 as acceleration due to gravity. The answer might be different from what you expect