water is flowing through a 10 cm diameter hose on the first floor of a building
ID: 1617814 • Letter: W
Question
water is flowing through a 10 cm diameter hose on the first floor of a building with a speed of 12 m/'s and an absolute pressure of 400 kpa the hose carries the water to the second story of the building and a height of 3.40 above its starting point where it exist the hose through a nozzle if a diameter 4.0 cm what is the speed of the water as it leaves the nozzle. what is the absolute pressure inside the nozzle.
Explanation / Answer
We solve this equation using the Bernoulli's equation in the Pressure head:
P1 +.5(rho)gh1 + .5(rho)v12 = P2 +.5(rho)gh2 + .5(rho)v22
(400000) + (.5x1000x9.8x0) + (.5x1000x144) = P2 + (.5x1000x9.8x3.4) + (.5x1000x(v2)2)
Since the difference in h is not too much at 3.4m height, it means the velocity remains constant v2 = 12m/s
(We make this assumption because 400 kPa = 4 bar pressure means water can reach roughly 4/.098 i.e. > 40m height and since 40 >> 3.4m we can go ahead with this assumption)
Thus, 400000 = 4900x3.4 + P2
P2 = 366.65 kPa (absolute pressure inside the nozzle)
Now, we use the continuity equation, A1V1 = A2V2
(pi*10*10)(12) = (pi*4*4)(V2) Thus, V2 = 75m/s
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