According to Kepler,planets move in

For proposing the universal law of gravitation,which laws were taken for help?

Suppose a planet goes around the Sun with a linear speed twice as fast as that of the Earth. What will be its orbit size compared to that of the Earth? (Radius of Earth $= R$)

Which of the following orbits is a possible orbit for a planet?

The time period of a satellite of earth is $24 \ hours$. If the separation between the earth and the satellite is decreased to one-fourth of the previous value,then its new time period will become $....... \ hours$.

$A$ satellite which is geostationary in a particular orbit is taken to another orbit. Its distance from the centre of the Earth in the new orbit is $2$ times that of the earlier orbit. The time period in the second orbit is: