Question
A hot air balloon is carrying some passengers, and a few sandbags of mass 1   kg each so that its total mass is 480   kg . Its effective volume giving the balloon its buoyancy is V . The balloon is floating at an equilibrium height of 100   m . When N number of sandbags are thrown out, the balloon rises to a new equilibrium height close to 150   m with its volume V remain unchanged. If the variation of the density of air with height h from the ground is ρ h = ρ 0 e - h h 0 , where ρ 0 = 1 . 25   kg   m - 3 and h 0 = 6000   m , the value of N is _________.