Question

A conical tank (D=1.6 m, H=4 m) is initially full of a liquid (ρ=900 kg/m3). The top surface of this liquid is exposed to air; and rate of evaporation of the liquid is given to be proportional the exposed surface. The radius r for any level of the tank is given as: r = 0.8 - 0.00358t, where r is in meters, and t is time in hours. Determine the rate evaporation of the liquid, in kg/h, after 5 hours.