Proper velocity the traveling object. It equals the object's momentum p divided by its rest mass "m", and is made up of the space-like components of the object's four-vector velocity. William Shurcliff's monograph mentioned its early use in the Sears and Brehme text. Fraundorf has explored its pedagogical value while Ungar, Baylis and Hestenes have examined its relevance from group theory and geometric algebra perspectives. Proper velocity is sometimes referred to as celerity. Unlike the more familiar coordinate velocity v, proper velocity is synchrony-free (does not require synchronized clocks) and is useful for describing both super-relativistic and sub-relativistic motion. Like coordinate velocity
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