A12.0-kg shell is launched at an angle of 55.0 ∘ above the horizontal with an initial speed of 150 m/s. when it is at its highest point, the shell exploded into two fragments, one three times heavier than the other. the two fragments reach the ground at the same time. assume that air resistance can be ignored. if the heavier fragment lands back at the same point from which the shell was launched, where will the lighter fragment land and how much energy was released in the explosion