Question

How does mass affect orbital speed?

Answer 1

Assuming we are talking about the mass of the satellite (and not the mass of the body being orbited), mass does not affect the orbital speed.

Explanation:

Kepler's 3rd Law of Planetary Motion says that

`T^2 = (4*pi^2*r^3)/(GM)`

`T` is the period of the orbit. That and the radius of the orbit determine the orbital speed.

The terms `(4*pi^2)/G` from that equation are constants. I will assume you want to compare masses without changing radius, so I will assume that the entire expression `(4*pi^2*r^3)/G` is to be considered constant.

It is unclear which mass you are asking about. There is the mass of the satellite and the mass of the body being orbited to be considered.

I will first assume you are asking about the mass of the satellite. The mass of the satellite is not part of the expression `(4*pi^2*r^3)/(GM)`. Therefore we can conclude that mass of the satellite does not affect orbital speed.

Now I will assume you are asking about the mass of the body being orbited. The mass of that body is the `M` in the expression `(4*pi^2*r^3)/(GM)`. Therefore if `M` increases, the value of `T` will decrease indicating that the speed has increased.

I hope this helps,
Steve