Two identical massless springs of constant k = 200n/m are fixed at opposite ends of a level track, as shown. a 5 kg block is pressed against the left spring, compressing it by 0.15m. the block is then released from rest. the entire track is frictionless except for the region of length 0.25m between a and b, where mk = 0.08.

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.