1. The force of gravitational attraction between two planets is given by the equation

F = $\frac{G{m}_{1}{m}_{2}}{{r}^{2}}$

Where m₁ and m₂ are the masses of the two planets and r is the separation between their centres of mass. G is the gravitational constant and has value 6.67 × 10^–11 N m² kg^–2.

The magnitude of the gravitational field strength for a planet is given by

g = $\frac{GM}{{r}^{2}}$

Where r = the distance from the centre of the planet and M is the mass of the planet.

An object of mass 6 kg falls from rest on each of the two planets, which have no atmospheres. On planet 1, which has a radius of 12000 km, it reaches a velocity of 20 m s^–1 after 20 m. On planet 2, which has radius of 5000 km, it falls a distance of 120 m in 10 s. 

If the gravitational force between the two planets is 37 TN, what is the distance between them?