how can you make the gravitational force between two 50kg objects less than the gravitational force between two 5kg objects

By increasing the distance between the two 50 kg objects compared with the distance between the 5 kg objects.

Explanation:

The formula for the force between 2 objects is

Fg = (G m1 m2) / r^2

where Fg is the force, G = gravitational constant, m1 and m2 are the masses of the objects and r = the distance between the objects.

So as r is increased Fg is decreased.

The gravitational force between two 50kg objects could be less than the gravitational force between a 50kg and a 5kg object if the two 50kg objects are much farther apart.