Steve VanDevender writes: > K = m * ((1 / sqrt(1 - v^2/c^2)) - 1) Actually, for the units on that to work out right, it should be either: K = m * c^2 * ((1 / sqrt(1 - v^2/c^2)) - 1) or K = m * ((1 / sqrt(1 - v^2)) - 1) (where v is a fraction of c).