Sir, A tank is filled with water (density 1000 kg/m^3) and oil(density 900 kg/m^3). The height of water layer 1 metre and that of oil layer is 4 metre. If g=9.8 m/s^2, then what is the velocity of efflux from an opening at the bottom of the tank? I solved it the following way. Let d1 be the density of water and d2 be the density of oil. Let h1 and h2 be the height of water and oil layer respectively. Total pressure head = Pressure head due to 1 metre water + Pressure head due to 4 metre oil =[ h1d1g]/[d1g] + [h2d2g]/[d1g] = h1 + [h2d2]/d1 = 1 + [4x900]/1000 = 4.6 metres of water column Pressure energy is converted into kinetic energy. P = ½(d1)(v^2) [4.6x1000xg]= ½(1000)(v^2) v^2 = 2x4.6x9.8 v = 9.5 m/s^2 Is it right? Here the symbol ^ denotes power.