According to Kepler, planets move in

The distance between Sun and Earth is $R.$ The duration of year if the distance between Sun and Earth becomes $3R$ will be 

A planet takes $200$ days to complete one revolution around the Sun. If the distance of the planet from Sun is reduced to one fourth of the original distance, how many days will it take to complete one revolution

Kepler discovered

A planet revolving in elliptical orbit has

$(A)$ a constant velocity of revolution.

$(B)$ has the least velocity when it is nearest to the sun.

$(C)$ its areal velocity is directly proportional to its velocity.

$(D)$ areal velocity is inversely proportional to its velocity.

$(E)$ to follow a trajectory such that the areal velocity is constant.

Choose the correct answer from the options given below

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