escape velocity

Escape  velocity

In the universe massive bodies have bounded all small bodies with bound energy, Now to escape small bodies from the surface of massive bodies gravitational field influence, You must required a minimum velocity to free small object from massive bodies surface, this minimum velocity is know as escape velocity.

What is escape velocity 

Escape velocity of a planet is that minimum velocity given to an object on that planet due to which it will just escape the planet and will never come back again on that planet.

When you through an object from the surface of the Earth, it goes up some height and then start fall back towards  the Earth surface, This happen due to gravitational field attraction by Earth around it.

Earth gravity acts vertically downward continuously and due to this object speed decrease continuously at per second  9.8 m/s and finally reaches at a height at which final speed becomes zero, but gravity acceleration acting downward and then object start coming back towards surface of the Earth similarly every second speed increase 9.8 m/s and finally reaches the Earth Surface. 

But when you will through the object with so much high velocity that it will reach very high where gravity pulling effect vanishes and then the object velocity becomes zero that that point object will stop in space and will never come back on the Earth surface that minimum through velocity is escape velocity.

See the below picture.

                                                                 

Escape Velocity