A projectile of mass M is moving in the +x direction with speed V when it explodes into two fragments: a lighter one having mass M/4 and a heavier one having mass 3M/4. The heavier fragment moves in the -y direction with speed V. What is the speed of the lighter fragment? (Assume there are no external forces acting on the system). A) V B) 2V C) 3V D) 4V E) 5V ------ So the momentum after is equal to the momentum before. So... mVbx = (1/4)mvx + (3/4)mVx mVbx = (1/4)mvx + (0) mVbx = (1/4)mvx => vx = 4Vb So... mvby = (1/4)mvy + (3/4)mVy => vy = Vb Thus... 4vb+vb = 5vb The answer is E, correct? Can somebody please look over this and confirm whether this is right or wrong? I'm not too confident. Thanks guys!