The gravitational force between two objects is given by:
[tex]F=G \frac{m_1 m_2}{r^2} [/tex]
where
G is the gravitational constant
m1 and m2 are the two masses
r is the separation between the two objects
In our problem, [tex]m_1 = 54 kg[/tex], [tex]m_2=66 kg[/tex] and [tex]r=9 m[/tex], so the gravitational force between the two objects is
[tex]F= (6.67 \cdot 10^{-11} m^3 kg^{-1} s^{-2}) \frac{(54 kg)(66 kg)}{(9 m)^2} =2.9 \cdot 10^{-9}N[/tex]
