# What is Escape Velocity?

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.

## Escape Velocity Formula

There is a formula for working out the escape velocity.

• G is the Universal Gravitational Constant (6.673 x 10-11 N . M2/kg2)
• M is the Mass of the planet or Moon in Kg
• R is the Radius of the planet m

## Why is Escape Velocity important?

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.

## What are the Escape Velocities of the Planets?

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) Mercury 0.33011 2439.7 4.3 Venus 4.8675 6051.8 10.36 Earth 5.9723 6378.14 11.186 Mars 0.64171 3396.2 5.03 Jupiter 1898.19 71492 59.5 Saturn 568.34 60268 35.5 Uranus 86813 25559 21.3 Neptune 102.413 24764 23.5 Pluto 0.01303 1187 2.21