A satellite travels with a constant speed |v| as it moves around a circle centered on the earth. How much work is done by the gravitational force F on the satellite after it travels half way around the earth in time t?

W = 0

Explanation:

As the satellite moves in a circle the force is perpendicular to the path, therefore the work that is defined by

      W = F. r = f r cos θ

Since the force and the radius are perpendicular, the angle θ = 90º and the cosine 90 = 0, therefore there is no work for the circular motion.

W = 0

one person pulls 90n one way and the other has 100n pulling the other way.

so the net force = 90 - 100 = -10n,

or the ans can be 10n if the picture shows -90n and 100n instead.