(a)[1]
Define gravitational field strength in words.
(b)
The star nearest to it is Proxima Centauri. This star has a mass of $2.5 \times 10^{29}\ \text{kg}$ and lies $4.0 \times 10^{13}\ \text{km}$ from the Sun. The Sun has a mass of $2.0 \times 10^{30}\ \text{kg}$.
(b(i))[1]
State why Proxima Centauri may be assumed to be a point mass as seen from the Sun.
(b(ii).1)[2]
Calculate the gravitational field strength produced by Proxima Centauri at a separation of $4.0 \times 10^{13}\ \text{km}$.
(b(ii).2)[2]
Calculate the gravitational force of attraction acting between the Sun and Proxima Centauri.
(c)[2]
Suggest, using numbers, why it may be assumed that the Sun is isolated in space from other stars.