Define gravitational field strength in words.
An isolated star has radius $R$. The star’s mass can be treated as though it were a point mass at the centre of the star. The gravitational field strength at the star’s surface is $g_s$. On Fig. 1.1, sketch a graph to show how the gravitational field strength of the star changes with distance from its centre. Consider distances in the range $R$ to $4R$.
The Earth and the Moon may be treated as spheres isolated in space, with all their mass concentrated at their centres. Their masses are $6.00 \times 10^{24}\,\text{kg}$ and $7.40 \times 10^{22}\,\text{kg}$ respectively. The Earth’s radius is $R_E$, and the centre-to-centre separation of the Earth and Moon is $60R_E$, as shown in Fig. 1.2.
Explain why there is a point between the Earth and the Moon where the gravitational field strength is zero.
Determine the distance, in terms of $R_E$, from the centre of the Earth at which the gravitational field strength is zero.
On the axes in Fig. 1.3, sketch a graph showing how gravitational field strength changes with position between the Earth’s surface and the Moon’s surface.