The size of the gravitational potential at the surface of a planet of radius $R$ is $\phi$. Treat the planet as an isolated sphere. On Fig. 2.1, sketch how the gravitational potential varies with distance $x$ from the centre of the planet for $R \le x \le 4R$.
A satellite is in a geostationary orbit above the Earth. At $t = 0$, the magnitude of the gravitational potential due to the Earth at the satellite’s position is $\phi$. On Fig. 2.2, sketch how the gravitational potential due to the Earth at the satellite’s position varies for $t$ from $t = 0$ to $t = 24\,\text{hours}$.
The electric potential difference (p.d.) between two parallel plates is $V$, as shown in Fig. 2.3. The separation of the plates is $d$. The space between the plates is a vacuum. On Fig. 2.4, sketch how the electric potential varies with distance from the positive plate.