# Elliptical orbits of planets

As we know, the velocity of the planet changes as it orbits around the sun, both in its magnitude and direction. The centripetal acceleration causes the change in the direction of velocity but I want to know what is the tangential force that acts on the planet to change the velocity by its $$magnitude$$.

The answer normally as to why the speed changes is:

If the force that the Sun exerts on the planet increases (as the planet moves closer), then the acceleration of the planet must increase, resulting in a higher orbital speed, and vice versa.

But this force is not along the body but towards the sun. So such a force should only change its direction.

• Where do you think the force that changes direction comes from? Do you realize that force is a vector? What research have you done? – Bill N Dec 29 '20 at 15:58