If the masses of two point objects are tripled and the distance between them is doubled,then the gravitational force of attraction between them will increase by .......... $\%$

The gravitational force between a hollow spherical shell (of radius $R$ and uniform density) and a point mass $m$ is $F$. Show the nature of the $F$ versus $r$ graph,where $r$ is the distance of the point mass from the centre of the hollow spherical shell.

The value of $G$ on Earth is $6.67 \times 10^{-11} \ Nm^2/kg^2$. What is the value of $G$ on the Moon?

Two objects are placed at a certain distance from each other in air. If they are placed at the same distance in water,what is the ratio of the gravitational force between them?

Regarding fundamental forces in nature,the correct statement is

According to Newton's law of gravitation,both the Earth and an apple exert equal forces on each other. Why does the apple fall towards the Earth,but the Earth does not move towards the apple?