Question

Al the astronaut has a weight of 1600 N when he is standing on the surface of earth. What is the force of gravity action on him when he is in space station orbiting earth at a distance of four earth radii from the center of the earth?

Answer 1

force of gravity?
F=1600/4^2
net force is zero, of course, as he is in orbit.

Answer 2

Your answer is correct, but the net force of an orbiting object is not zero. Objects in circular motion have a net force that points to the center of the circle that generates the centripetal force