In the atmosphere of a planet or large satellite the hot molecules or atoms may be moving fast enough to escape the gravitational potential well that confines the atmosphere to the planet. Why does hydrogen escape more easily than carbon dioxide?
The escape velocity from a massive object is the speed needed to reach an infinite distance from it and have just slowed to a stop, that is, to have just enough kinetic energy to climb out of the gravitational potential well and have none left. You can find the escape velocity by equating the total kinetic and gravitational potential energy to zero
E=12mv2esc−GmM/r=0E=12mvesc2−GmM/r=0
vesc=2GM/r−−−−−−√vesc=2GM/r
where GG is Newton's constant of gravitation, MM is the mass of the object from which the escape is happening, and rr is its radius. This is physics you have seen in the first part of the course, and you should be able to use it to find an escape velocity from any planet or satellite. For the Earth, for example the escape velocity is about 11.2 km/s, and for the Moon it is 2.38 km/s. A very important point about escape velocity: it does not depend on what is escaping. A spaceship or a molecule must have this velocity or more away from the center of the planet to be free of its gravity,
1. In the atmosphere of a planet or large satellite the hot molecules or atoms may be moving fast enough to escape the gravitational potential well that confines the atmosphere to the planet. Why does hydrogen escape more easily than carbon dioxide?
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