Assertion :A geostationary satellite rotates in a direction from west to east.
Reason : At midnight when the sun is directly below, it pulls on an object in the same direction as the pull of the earth on that object. At noon when the sun is directly above , its pulls on an object in a direction opposite to the pull of the earth.

A cosmonaut is orbiting earth in a spacecraft at an altitude $h=630 \mathrm{km}$ with a speed of $8 \mathrm{km} {\mathrm{s}}^{-1}$. If the radius of the earth is $6400 \mathrm{km}$, the acceleration of the cosmonaut is

Four identical particles of mass $\mathrm{M}$ are located at the corners of a square of side $‘a’$ . What should be their speed if each of them revolves under the influence of other’s gravitational field in a circular orbit circumscribing the square?