Three particles $A, B$ and $C$ each of mass $m$ are lying at the corners of an equilateral triangle of side $L$. If the particle $A$ is released keeping the particles $B$ and $C$ fixed,the magnitude of instantaneous acceleration of $A$ is ........

The mass of the Earth has been determined through:

$A$ rocket is fired from the Earth towards the Sun. At what distance from the Earth's centre is the gravitational force on the rocket zero? Mass of the Sun $= 2 \times 10^{30} \; kg$,mass of the Earth $= 6 \times 10^{24} \; kg$. Neglect the effect of other planets,etc. (Orbital radius $= 1.5 \times 10^{11} \; m$)

Two point masses $A$ and $B$ having masses in the ratio $4 : 3$ are separated by a distance of $1\, m$. When another point mass $C$ of mass $M$ is placed in between $A$ and $B$,the gravitational force between $A$ and $C$ is $\frac{1}{3}$ of the gravitational force between $B$ and $C$. Then the distance of $C$ from $A$ is:

What is the strength of the gravitational force compared to the strong nuclear force?

Find the acceleration of our galaxy due to the nearest comparably sized galaxy. The approximate mass of each galaxy is $8 \times 10^{11}$ solar masses,and they are separated by $2 \times 10^6$ light-years. Each galaxy has a diameter of $10^5$ light-years. (Assume $1 \text{ light-year} \approx 10^{16} \text{ m}$,gravitational constant $G \approx 10^{-10} \text{ Nm}^2/\text{kg}^2$,and mass of the Sun $= 2.0 \times 10^{30} \text{ kg}$)