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 $O$?

If gravitational potential in a region is given by $V = 4x^2$,then the gravitational field is:

In a gravitational field,the gravitational potential is given by $V = -\frac{K}{x} \ (J/kg)$. The gravitational field intensity at point $(2, 0, 3) \ m$ is

The mass density of a solid sphere is $\rho$. The radius of the sphere is $R$. The gravitational field at a distance $r$ from the centre of the sphere inside it is:

The mass density inside a solid sphere of radius $R$ varies as $\rho(r)=\rho_0\left(\frac{r}{R}\right)^\beta$,where $\rho_0$ and $\beta$ are constants and $r$ is the distance from the centre. Let $E_1$ and $E_2$ be gravitational fields due to the sphere at distances $\frac{R}{2}$ and $2R$ from the centre of the sphere,respectively. If $\frac{E_2}{E_1}=4$,the value of $\beta$ is

The mass of the moon is $\frac{M}{81}$,where $M$ is the mass of the earth. The distance between the earth and the moon is $60R$,where $R$ is the radius of the earth. At what distance from the center of the moon will the gravitational intensity be zero (in $R$)?