Q4. A stationary particle breaks into two parts of masses $m _ { A }$ and $m _ { B }$ which move with velocities $v _ { A }$ and $v _ { B }$ respectively. The ratio of their kinetic energies ( $K _ { B } : K _ { A }$ ) is :\\
(1) $v _ { B } : v _ { A }$\\
(2) $m _ { B } : m _ { A }$\\
(3) $m _ { B } v _ { B } : m _ { A } v _ { A }$\\
(4) $1 : 1$