# escape velocity

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## escape velocity,

the velocity a body must be given in order to escape the gravitational hold of some other larger body, e.g., the earth, moon, or sun. A body given less than the escape velocity will fall back toward the surface of the larger body; a body given a velocity equal to or greater than the escape velocity will still be attracted by the larger body, but this force will not be sufficient to cause it to return. Escape velocity depends on the mass of the larger body and the distance of the smaller body from its center, being proportional to the square root of the ratio of these two quantities. The velocity of escape from the earth at its surface is about 7 mi (11.3 km) per sec, or 25,000 mi per hr; from the moon's surface it is 1.5 mi (2.4 km) per sec; and for a body at the earth's distance from the sun to escape from the sun's gravitation, the velocity must be 26 mi (41 km) per sec.

## escape velocity

The minimum velocity required for an object to enter a parabolic trajectory around a massive body and hence escape from its vicinity. The object will keep moving away from the body although it travels at decreasingly lower speeds as the massive body's gravitational attraction continues to slow it down. If the object does not attain escape velocity it will enter an elliptical orbit around the body. If escape velocity is exceeded the object will follow a hyperbolic path. The escape velocity at a distance r from the center of a massive body, mass m , is given by √(2Gm /r ), where G is the gravitational constant. The escape velocity from the Earth's surface is about 11.2 km s–1, from the Moon 2.4 km s–1, and from the Sun 617.7 km s–1. For a massive body to retain an atmosphere the average velocity of the gas molecules must be well below escape velocity.

## escape velocity

[ə′skāp və‚läs·əd·ē]
(astronomy)
The minimum speed away from a parent body that a particle must acquire to escape permanently from the gravitational attraction of the parent.

## escape velocity

the minimum velocity that a body must have in order to escape from the gravitational field of the earth or other celestial body
References in periodicals archive ?
A very massive event would point towards a dense environment with large escape speed'.
'Escape speed of stellar clusters from multiple-generation black-hole mergers in the upper mass gap'.
In faster individuals, it may be advantageous to flee at farther distances, since there is a higher probability that the individual will survive entirely on the basis of escape speed. In slower individuals with less chance of escaping solely on the basis of speed, individuals may rely on crypsis to escape detection.
Flight distances were determined for thirty-eight of the individuals (19 males, 19 females) whose escape speeds had been measured.
Among species, escape speed closely matches maximal speed (mean of all species = 90.6% [+ or -] 3.80 SE).
Sprinting ability during feeding is intermediate (about 71%) between field escape speed and field undisturbed activity speed.
Not only is the skeletal system designed for maximum efficiency, but the resultant body form further allows copepods to attain and maintain maximum observed escape speeds of 1 m [s.sup.-1] (Fields and Yen, 1997) to enter into the inertial realm of Re = 1000.

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