Escape Velocity is the term used to describe the speed (velocity) that an object (A) needs to be able to break away (escape) from another object's (B) Gravity. (A) can be anything such as a spaceship or a rocket whereas (B) is a planet, a star or anything else.
Gravity is the weakest of the four forces of nature which also includes Strong Nuclear, Weak Nuclear and Electromagnetic. You are stronger than gravity, you can prove that by jumping. Jumping will not give you the necessary velocity to break from the Earth totally.
Anything that has gravity will require an escape velocity in order to break from it. The larger the object is, the greater the escape velocity is needed to break away from it. The Escape Velocity of Mars is less than that of the Earth which is less than that of Jupiter.
There is a formula for working out the escape velocity.
If you don't know the escape velocity of an object, you will never be able to break free from its gravity and will forever be stuck on it. The planet with the lowest escape velocity is Mercury as it is the smallest planet and Jupiter having the highest escape velocity.
If Apollo 11 didn't know the escape velocity of the moon then they wouldn't know how much speed they would need to break free from the moon and rendezvous with the orbiter to take them home. The escape velocity of the Earth is 11.2 Km/s whereas the escape velocity of the Moon is a mere 2.38 which is why the astronauts didn't need a large Saturn V rocket to get them back once they had landed.
Below are the escape velocities of the eight planets plus that of the ex-planet, Pluto.
|Planet||Mass (1024)kg||Radius||Escape Velocity (km/s)|
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