An explosive shell, with total mass 80 kg is launched vertically into the air from a mortar. The shell explodes in flight and breaks into two parts with masses of 30 kg and 50 kg (assume the mass of the explosive is negligible). The portions land at the same time. The 30 kg portion of the shell lands 1000 m from the mortar. Determine where the other portion of the shell landed, explaining the physical principles that you applied to find your answer.