$3$ particles each of mass $m$ are kept at the vertices of an equilateral triangle of side $L$. The gravitational field at the centre due to these particles is

The gravitational force on a body of mass $1.5 \,kg$ situated at a point is $45 \,N$. The gravitational field intensity at that point is ......... $N/kg$.

Two concentric hollow spheres of radius $R$ and $2R$ have the same mass $M$,as shown in the figure. The gravitational field intensity at point $P$ (where $R < r < 2R$) is:

Gravitational mass is proportional to gravitational

Six objects are placed at the vertices of a regular hexagon. The geometric centre of the hexagon is at the origin with objects $1$ and $4$ on the $X$-axis (see figure). The mass of the $k$-th object is $m_k = k^i M |\cos \theta_k|$, where $i$ is an integer, $M$ is a constant with the dimension of mass, and $\theta_k$ is the angular position of the $k$-th vertex measured from the positive $X$-axis in the counter-clockwise sense. If the net gravitational force on a body at the centroid vanishes, the value of $i$ is

Two identical heavy spheres are separated by a distance $10$ times their radius. Will an object placed at the mid-point of the line joining their centres be in stable equilibrium or unstable equilibrium? Give reason for your answer.