Question

Which force diagram accurately represents a satellite in orbit around Earth?

A free body diagram with a dot and a vector pointing down labeled F Subscript g Baseline.

A free body diagram with a dot and a vector pointing down labeled F Subscript g Baseline and a vector left labeled F Subscript p Baseline.

A free body diagram with a dot and a vector pointing down labeled F Subscript g Baseline and a vector left labeled F Subscript p Baseline. A vector to the right labeled F Subscript air Baseline.

A free body diagram with a dot and a vector pointing down labeled F Subscript g Baseline and a vector to up labeled F Subscript air Baseline and both vectors are the same length.

Answer 1

The first diagram: a single force vector pointing toward Earth labeled F_g.

Reason: an orbiting satellite (neglecting tiny atmospheric drag or thruster firings) has only gravity acting on it. That gravitational force provides the required centripetal acceleration. There is no separate "centripetal" force (that's just the name for the net inward force) and there is no upward air force in space.