The gravitational force F acting between two objects of mass m and m' kept at a distance of r from their centres is
1
\(F \propto \frac{mm'}{r}\)
2
\(F \propto \frac{r^2}{mm'}\)
3
\(F \propto \frac{(mm')^2}{r}\)
4
\(F \propto \frac{mm'}{r^2}\)
The gravitational force F acting between two objects of mass m and m' kept at a distance of r from their centres is