# Physics Concepts for JEE 2016: Advance Illustrations of Gravitational Field and Satellite Motion (Set III)

A body projected from a satellite: When a body is projected from a satellite at some speed with respect to it, its net projection velocity will be the vector sum of its velocity with respect to  the satellite and the velocity of the satellite. Depending upon the net velocity gained, the path of body can be analysed. Watch the Illustration video given below for understanding of such a case.

https://youtu.be/v3yFmghba2A

Effect of shrinking earth on gravity: If we consider that the earth starts shrinking due to some reason, it will affect the gravity on the earth’s surface. Watch the Illustration video below to analyse the similar situation.

https://youtu.be/L5FnhJsCFnI

Escape velocity due to gravity of two planets: We have already discussed about the escape velocity of a body when it is thrown from the surface of a planet. To understand the concept of escaping a body from a point where a body is moving under the influence of two planets, watch the illustration video below for this. Similar case can be extended further for more than two planets also.

https://youtu.be/XpVk9TI4yHE

A particle moving inside a spherical cavity: We have already analysed the gravitational field due to a solid sphere. If inside the sphere we make a cavity and a particle’s motion is to be analysed in this cavity, we first need to understand the gravitational field inside the cavity. Watch the Illustration video below to understand such a case.

https://youtu.be/xq7V1ErJTn8