Weightlessness experienced while orbiting the earth in a spaceship is the result of:

$A$ satellite is to be placed in an equatorial geostationary orbit around the Earth for communication.
$(a)$ Calculate the height of such a satellite.
$(b)$ Find out the minimum number of satellites that are needed to cover the entire Earth,so that at least one satellite is visible from any point on the equator.
Given: $M = 6 \times 10^{24} \ kg$,$R = 6400 \ km$,$T = 24 \ h$,$G = 6.67 \times 10^{-11} \ N \cdot m^2/kg^2$.

The radius of the orbit of a geostationary satellite is (mean radius of earth is $R$,angular velocity about own axis is $\omega$,and acceleration due to gravity on earth's surface is $g$).

The orbit of a geo-stationary satellite is circular. The time period of the satellite depends on:
$(i)$ mass of the satellite
(ii) mass of the earth
(iii) radius of the orbit
(iv) height of the satellite from the surface of the earth
Which of the following is correct?

$A$ ball is dropped from a spacecraft revolving around the earth at a height of $120 \, km$. What will happen to the ball?

Two satellites of mass $50\,kg$ and $100\,kg$ revolve around the earth in circular orbits of radius $9\,R$ and $16\,R$ respectively,where $R$ is the radius of the earth. The ratio of the speeds of the two satellites will be: