Q.If the masses of the Earth and Sun suddenly doubled, gravitational force between them will:

Newton's Law of Universal Gravitation

Every particle of matter attracts every other particle with a force directed along the line joining them. For two point masses $m_1$ and $m_2$ separated by a distance $r$, the magnitude of the attraction is

where $G = 6.67 \times 10^{-11}\ \text{N m}^{2}\,\text{kg}^{-2}$ is the universal gravitational constant. The force is attractive, acts along the line of centres, and obeys Newton's third law (equal and opposite on the two bodies). Its defining feature is the inverse-square dependence on separation.

Superposition. When several masses act on a body, the net gravitational force is the vector sum of the individual forces. For an extended body — a rod, ring or shell — the body is treated as a collection of point-mass elements and the contributions are integrated. For a uniform ring of mass $M$ and radius $R$, the force on a point mass $m$ placed on its axis at distance $h$ from the centre is directed along the axis and has magnitude

$F = \frac{G M m\, h}{\left(R^{2} + h^{2}\right)^{3/2}},$ …