$A$ mass $m$ is placed at point $P$ on the axis of a ring of mass $M$ and radius $R$ at a distance $R$ from its centre. The gravitational force on mass $m$ is

If the distance between the centres of Earth and Moon is $D$ and the mass of Earth is $81$ times that of the Moon,at what distance from the centre of Earth will the gravitational field be zero?

Two masses $90 \ kg$ and $160 \ kg$ are separated by a distance of $5 \ m$. The magnitude of the intensity of the gravitational field at a point which is at a distance $3 \ m$ from the $90 \ kg$ mass and $4 \ m$ from the $160 \ kg$ mass is (Universal gravitational constant,$G=6.67 \times 10^{-11} \ N \ m^2 \ kg^{-2}$)

The gravitational field,due to the 'left over part' of a uniform sphere (from which a part as shown,has been 'removed out'),at a very far off point,$P$,located as shown,would be (nearly)

Consider a ring of mass $m$ and radius $r$. The maximum gravitational intensity on the axis of the ring has a value of:

Infinite particles,each of mass $3 \ kg$,are placed at distances of $1 \ m, 2 \ m, 4 \ m, 8 \ m, \dots$ from point $O$. What is the gravitational intensity at point $O$?