Quick questions on Gravitational fields and orbits explained: H2 Physics Newtonian Mechanics

The gravitational field strength at a point is the force per unit mass:

The gravitational potential at a point is the work done per unit mass to bring a small mass from infinity to that point:

The relation $T^2 \propto r^3$ is Kepler's third law, here derived from Newtonian gravity. It applies to all bodies orbiting the same central mass and lets you compare orbits without knowing $G$ or $M$ directly.

A geostationary satellite stays fixed above a point on the equator. This requires three conditions: a period of one sidereal day (about $24$ hours), an orbit in the equatorial plane, and motion from west to east. Because the period is fixed, Kepler's third law fixes the radius at a single value of about $4.2 \times 10^7\ \text{m}$ from the Earth's centre.

State Newton's law of gravitation and define each symbol. [2 marks]

Show that the orbital speed of a satellite is independent of its own mass. [2 marks]

Explain why a geostationary satellite has only one possible orbital radius. [3 marks]