A geostationary satellite orbits around the earth in a circular orbit of radius $36000 \mathrm{km}$. Then, the time period of a spy satellite orbiting a few hundred kilometre's above the earth's surface $\left(R_{\mathrm{earth}}=6400 \mathrm{km}\right)$ will approximately be

In a satellite if the time period is $T$, then $K\mathit{,}\mathit{ }E$, is proportional to

An artificial satellite revolves around the earth in circular orbit with a speed $v$. If $m$ is the mass of the satellite, its total energy is

If a missile launched with a velocity less than escape velocity, the sum of its $K.E$. and $P.E$. is always

The kinetic energy required to make a body to move to infinity from the earth's surface is