Which force is responsible for the necessary centripetal force of a satellite revolving around the Earth?

$A$ satellite is revolving very close to a planet of density $\rho$. The period of revolution of the satellite is

$A$ satellite can be in a geostationary orbit around a planet at a distance $r$ from the centre of the planet. If the angular velocity of the planet about its axis doubles,a satellite can now be in a geostationary orbit around the planet if its distance from the centre of the planet is

Two satellites $A$ and $B$ go round a planet $P$ in circular orbits having radii $4R$ and $R$ respectively. If the speed of the satellite $A$ is $3V$,the speed of the satellite $B$ will be ........ $V$.

$A$ comet orbits the Sun in a highly elliptical orbit. Does the comet have a constant $(a)$ linear speed,$(b)$ angular speed,$(c)$ angular momentum,$(d)$ kinetic energy,$(e)$ potential energy,$(f)$ total energy throughout its orbit? Neglect any mass loss of the comet when it comes very close to the Sun.

$A$ satellite is moving around the earth with speed $v$ in a circular orbit of radius $r$. If the orbit radius is decreased by $1\%$,its speed will