Question

At what location does an artificial Earth satellite in elliptical orbit have it's greatest speed?

a)Nearest the Earth

b)Farthest from the Earth

c)Between the Earth and the Moon

d)Between the Earth and the Sun

Answer 1

It has its greatest speed at the point called "perigee," which is just a fancy name for its closest approach to the earth.

This can be explained in terms of conservation of energy and angular momentum and such; but maybe the simplest way to look at it is as follows:

In cases where gravity is the only force acting on an object, the object's motion follows these rules:
* When the object goes farther from the earth, it slows down;
* When the object goes closer to the earth, it speeds up.

From this simple principle, you can see that the object's greatest speed occurs when it's closest to the earth.