A village maintains a large tank with an open top, containing water for emergencies. The water can drain from the tank through a hose of diameter 6.60cm. the hose ends with a nozzle of diameter 2.20 cm. A rubber stopper is inserted into the nozzle. the water level in the tank is kept 7.50 m above the nozzle. a) Calculate the friction force exerted on the stopper by the nozzle. b) the stopper is removed. What mass of water flows from the nozzle in 2.00hours? c)Calculate the Gauge pressure of the flowin water in the hose just behind the nozzle. Ok so part a I did by using Bernoulli's Equation, finding pressure by assuming the pressure at a point on the waters surface at the top of the tank to be atmospheric, and that the pressure at the nozzle is some pressure P + atmospheric pressure, atmospheric pressure cancels, and resulting pressure is just density H20 X g X 7.50m = 73600 Pa. Sound good so far? Part b i did by saying pressure is F/A so F=P X A, after finding the area of the nozzle. Then that force has to equal the friction force because we assume the stopper not to be moving (equilibrium), (also assume stopper has same area as nozzle). turned out to be -28.0N. Is that OK too?? Then part c has me stuck, what is gauge pressure exactly? and how do you find it for this situation, I read in my text that it is the absolute pressure minus the atmoshperic pressure? so in this case would it be 73600-101300? because that doesn't make much sense, or did I find the gauge pressure already??