Question

Knowing the constant g what will the gravitational force between two masses be if the gravitational force between them is 36n and the distance is tripled? answer

Answer 1

The gravitational force between two masses is given by:
$F=G \frac{m_1 m_2}{r^2}$
where
G is the gravitational constant
m1 and m2 are the two masses
r is the separation between the two masses

We see that the force is proportional to the inverse of the square of the distance: $F \sim \frac{1}{r^2}$
therefore, if the distance is tripled:
r'=3r
The force decreases by a factor 1/9:
$F \sim \frac{1}{(3r)^2}= \frac{1}{9} \frac{1}{r^2}$

Since the original force was 36 N, the new force will be
$F' = \frac{1}{9} (36 N)= 4 N$