Mass in special relativity (including the kinetic energy of the gas) only when it is measured in the center of momentum frame. Just as is the case for single particles, the calculated "rest mass" of such a container of gas does not change when it is in motion, although its "relativistic mass" does change. The container may even be subjected to a force which gives it an overall velocity, or else (equivalently) it may be viewed from an inertial frame in which it has an overall velocity (that is, technically, a frame in which its center of mass has a velocity). In this case,
Escape velocity "r" from the center of mass of the planet, whose mass is "M". Its initial speed is equal to its escape velocity, formula_6. At its final state, "f", it will be an infinite distance away from the planet, and its speed will be negligibly small and assumed to be 0. Kinetic energy "K" and gravitational potential energy "U" are the only types of energy that we will deal with, so by the conservation of energy, "K" = 0 because final velocity is zero, and "U" = 0 because its final distance is infinity, so where μ is the standard gravitational