# Physics for JEE 2016: Introduction to Satellite Motion and Energy of a Satellite

A Satellite revolves around a planet in different orbits under the gravitational force of the planet. Here first we will discuss about the circular orbits in introduction and later we will also include the concepts related to motion of satellites in elliptical orbits.

For a stable circular motion around planet, a satellite requires necessary centripetal force which is provided by the gravity of the planet. At a specific altitude when a satellite revolves, then in the given orbital radius of the satellite, which is equal to sum of planet radius and altitude, a specific speed in satellite can deploy it in a stable orbit, at which gravitational force on satellite due to planet’s gravity will exactly provide the centripetal force required for its circular motion.

The same can also be explained in the frame of the satellite by using centrifugal force which balances the gravitational force by the planet. Watch the video below for the explanation of concept and calculation of orbital speed of satellite:

While in revolution around a planet, a satellite has two types of energies: 1. Kinetic Energy of its motion which can be calculated by using the orbital speed, and 2. Gravitational Potential Energy due to its interaction with the planet’s gravitational field. Sum of these two energies are taken as total energy of the satellite in motion. Watch the video below for the explanation and calculation of Satellite Energy: