Read the excerpt from a rumor of war. the tedium was occasionally relieved by a large-scale search-and-destroy operation, but the exhilaration of riding the lead helicopter into a landing zone was usually followed by more of the same hot walking, with the mud sucking at our boots and the sun thudding against our helmets while an invisible enemy shot at us from distant tree lines. the paradox in the excerpt illustrates the idea that

Consider an ordinary, helium-filled party 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. assuming that the balloon is at sea level, where the air density is 0.002377 slug/ft3, 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.