A lighter than air balloon and its load of passengers and ballast are floating stationary above the eart. Ballast is the wieght that can be dropped overboard to make the balloon rise. The radius of this balloon is 6.25m. Assuming a onstant value of 1.29 kg/m^3 for the density of air, determine how much weight must be dropped overboard to make the balloon rise 105m in 15.0s? I've been working on this one for a while and just keep getting nowhere!!