Why does the force of gravity change the speed of a satellite in an elliptical orbit?

1)The force of gravity is always tangent to the satellite motion.
2)Gravity speeds up the satellite as it moves away and slows it on its return.
3)The force of gravity is always perpendicular to the satellite motion.
4)Gravity slows the satellite as it moves away and speeds it up on its return.

The correct answer is 4) Gravity slows the satellite as it moves away and speeds it up on its return.

To understand why the speed of a satellite in an elliptical orbit changes due to the force of gravity, we need to consider the nature of the gravitational force. Gravity is a central force that always acts towards the center of the orbiting body. In the case of a satellite in an elliptical orbit, gravity is pulling the satellite towards the center of the planet it is orbiting.

When the satellite is closer to the planet (i.e., in the lower part of its elliptical path), the gravitational force is stronger. This stronger force causes the satellite to slow down since it has to overcome the gravitational pull. As a result, the satellite's speed decreases.

Conversely, as the satellite moves away from the planet (i.e., in the higher part of its elliptical path), the gravitational force weakens. With a weaker force, there is less resistance against the satellite's motion, allowing it to speed up. Therefore, the satellite's speed increases as it moves farther away from the planet.

In summary, the force of gravity slows down the satellite's speed as it moves closer to the planet and speeds it up as it moves farther away, resulting in a change in speed during its elliptical orbit.