Answer: option D. 20 Newtons
Explanation:
The force of gravity acts between any two objects having mass. The magnitude of force of gravity is directly proportional to the masses (M and m) of two bodies and inversely proportional to the square of the distance (r) between them.
[tex]F=G \frac{Mm}{r^2}[/tex]
where G is the gravitational constant.
[tex]F \propto \frac{1}{r^2}\\ \Rightarrow\frac{F_1}{F_2}=\frac{r_2^2}{r_1^2}\\ \Rightarrow \frac{5 N}{F_2}=\frac{(r_1/2)^2}{r_1^2} \\ \Rightarrow F_2 = 20 N[/tex]
Thus, if the distance between the two objects is reduced by half, the force would increase four times.
