A Gedanken Experiment - Continued
Critical Point: If we want momentum (=mv) to be conserved in the ? direction, then the mass of A must be appear to be greater than mass of B (according to B)!
Since velocity appears smaller by factor of ? , then mass must appear larger by the factor of ? in order for the product mv to be the same.
Mass increases with velocity! m = ? m0
m0 = mass measured at rest