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,
Division by zero cookie in half. The problem with 5 cookies and 0 people cannot be solved in any way that preserves the meaning of "divides". Another way of looking at division by zero is that division can always be checked using multiplication. Considering the example above, setting "x" = , if "x" equals ten divided by zero, then "x" times zero equals ten, but there is no "x" that, when multiplied by zero, gives ten (or any number other than zero). If instead of "x" = we have "x" = , then every "x" satisfies the question 'what number "x", multiplied by