1. The problem statement, all variables and given/known data An object, with mass 79 kg and speed 23 m/s relative to an observer, explodes into two pieces, one 5 times as massive as the other; the explosion takes place in deep space. The less massive piece stops relative to the observer. How much kinetic energy is added to the system during the explosion, as measured in the observer's reference frame? 2. Relevant equations KE=1/2mv^2 3. The attempt at a solution Since I have two masses, I don't know where to start on this problem. Any suggestions?