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 option 4) Gravity slows the satellite as it moves away and speeds it up on its return.
To understand why the force of gravity changes the speed of a satellite in an elliptical orbit, we need to consider Newton's law of gravitation. According to this law, the force of gravity between two objects is directly proportional to their masses and inversely proportional to the square of the distance between them.
In the case of a satellite in an elliptical orbit, as the satellite moves away from the object it is orbiting (such as a planet or a star), the distance between them increases. Since the force of gravity decreases with distance, the magnitude of the gravitational force acting on the satellite decreases. This reduction in the gravitational force leads to a decrease in the acceleration experienced by the satellite.
Consequently, as the satellite moves away from the object it is orbiting, its speed decreases. On the other hand, as the satellite comes closer to the object, the distance between them decreases, resulting in an increase in the gravitational force and, subsequently, in the acceleration experienced by the satellite. This increase in acceleration leads to an increase in the satellite's speed.
Therefore, in an elliptical orbit, gravity slows the satellite as it moves away and speeds it up as it comes closer to the object it is orbiting.