$A$ black hole is a:

Two particles each of mass $m$ are placed at points $P$ and $Q$ as shown in the figure. $R$ is the mid-point of $PQ = l$. The gravitational force on the third particle of mass $m$ placed at point $S$ on the perpendicular bisector of $PQ$ is

What is the vector form of the universal law of gravitation?

An astronaut of mass $m$ is working on a satellite orbiting the Earth at a distance $h$ from the Earth's surface. The radius of the Earth is $R$,while its mass is $M$. The gravitational pull $F_G$ on the astronaut is

Two particles of equal mass $m$ move in a circle of radius $R$ under the action of their mutual gravitational attraction. The speed of each particle is

Two identical solid copper spheres of radius $R$ are placed in contact with each other. The gravitational attraction between them is proportional to