consider an ordinary, helium-filled balloon with a volume of 2.2 ft3. the lifting force on the balloon due to the outside air is the net resultant of the pressure distribution exerted on the exterior surface of the balloon. using this fact, we can derive archimedes’ principle, namely that the upward force on the balloon is equal to the weight of the air displaced by the balloon. assume that the balloon is at sea level, where the air density is 0.002377 slug/ft3 and the pressure in the balloon is at the same pressure as exists in the surrounding air. calculate the maximum weight that can be lifted by the balloon. note: the molecular weight of air is 28.8 and that of helium is 4.