A hot-air balloon ascends at a constant rate.
(a) The weight of the balloon does (1) positive work, (2) negative work, (3) no work. Why?
(b) A hot-air balloon with a mass of 500 kg ascends at a constant rate of 1.50 m/s for 20.0s. How much work is done by the upward buoyant force? (Neglect air resistance.)