(This is expressed in a simplified non-vector form, assuming that the two velocities are in a single dimension. For vectors, the calculation <math>v_1 v_2</math> needs to be performed as a [[dot product]].) | (This is expressed in a simplified non-vector form, assuming that the two velocities are in a single dimension. For vectors, the calculation <math>v_1 v_2</math> needs to be performed as a [[dot product]].) |