Can the gravitational force of Earth do positive or negative work on a geosynchronous communication satellite, once it is on its circular orbit?

Question

Quizplus · Accepted Answer

The gravitational force of Earth is always perpendicular to the motion of a geosynchronous communication satellite in its circular orbit, therefore it cannot do any work on the satellite. The fact that the satellite has zero acceleration and constant speed only confirms that its kinetic energy is constant, but not related to the work done by gravity. Centripetal forces always do positive work, but in this case the gravitational force is not the centripetal force, as it does not change the direction of motion of the satellite.

Can the Gravitational Force of Earth Do Positive or Negative