A 10.0-{rm kg} shell is traveling horizontally to the right at 25.0 {rm m/s} relative to the ground when it explodes into two fragments, one of mass 3.00 {rm kg} and the other of mass 7.00 {rm kg}. The lighter fragment goes directly forward, and the explosion releases 1.50 × 103 {rm J} of mechanical energy to the fragments. Find the magnitude of the velocity of the heavier fragment relative to the ground just after the explosion.