### escape velocity

**(V**_{e})
(minimal velocity that allows something to overcome a body's gravity)

**Escape velocity** (**V**_{e})
is the velocity necessary to escape from
the gravity of a body such as a planet or star,
or group of bodies such as a galaxy.
Something moving as fast or faster than escape velocity will escape.
The escape velocity varies with position: if something is
set on a trajectory away from a planet at escape velocity,
it will slow, but after some slowing it will be at the
escape velocity for its new current position.
For a spherically-symmetric body distant from any other mass, the
magnitude of the escape velocity (i.e., speed) depends only
on the distance from the its center. Also, in such a case, the
necessary speed does not depend upon the direction: the same speed
will escape in any direction as long as its path does not intersect
with the body itself, i.e., it must not "hit the ground" while on its way.

The defining characteristic of a black hole is that its
gravity is so high that the escape velocity within a certain
surrounding region exceeds the speed of light in a vacuum, and nothing
can escape, not excepting EMR.

An object's escape velocity is that at which the kinetic energy of the object equals
(or more precisely, counterbalances) its potential energy due
to gravity of the body it is escaping. The velocity is easily
calculated by equating the two, given the law of gravity.

Example escape velocities:

escaping Earth from its surface | 11.186 km/s |

escaping the Moon from its surface | 2.38 km/s |

escaping Jupiter from its surface | 60.2 km/s |

escaping the Sun from its surface | 617.5 km/s |

escaping the solar system from 1 astronomical unit distance from the Sun | 42.1 km/s |

(*dynamics,gravity,measure,limit*)
http://en.wikipedia.org/wiki/Escape_velocity

http://hyperphysics.phy-astr.gsu.edu/hbase/vesc.html

**Referenced by:**

atmosphere

atmospheric escape

binding energy

Cassini

conic section

critical density (ρ_{c})

Einstein-de Sitter model

high-velocity star

hypervelocity star (HVS)

hydrodynamic escape

Jeans escape

long-period comet

potential energy (PE)

index