Which of the following quantities remains constant for a satellite in an orbit?

The orbital velocity of an artificial satellite in a circular orbit just above the Earth's surface is $v$. For a satellite orbiting at an altitude of half of the Earth's radius,the orbital velocity is

$A$ planet moves around the sun in an elliptical orbit with the sun at one of its foci. The physical quantity associated with the motion of the planet that remains constant with time is

Two satellites of masses $m$ and $4m$ are revolving in the same orbit around the Earth. Which one of the following statements is correct?

Choose the correct statement from the following: Weightlessness of an astronaut moving in a satellite is a situation of

The maximum and minimum distances of a comet from the Sun are $1.6 \times 10^{12} \ m$ and $8.0 \times 10^{10} \ m$ respectively. If the speed of the comet at the nearest point is $6 \times 10^{4} \ m/s$,the speed at the farthest point is ......... $\times 10^{3} \ m/s$.