Fluid Dynamics - The Burns Home Page

25/08/2010Question 21Question 22Water travels through a 9.6 cm radius fire hose with a speed of 1.3 m/s. At the endof the hose, the water flows out through a nozzle whose radius is 2.5 cm. What isthe speed of the water coming out of the nozzle? Suppose the pressure in the firehose is 350 kPa. What is the pressure in the nozzle?Av A v1 1 2 2r v r v2 21 1 2 2 2 m 0.096m 1.3 0.025m2v2 s mv 219sWater flows with constant speed through a garden hose that goes up a step 20.0cm high. If the water pressure is 143 kPa at the bottom of the step, what is itspressure at the top of the step?1 2 1 2PB gyB vB PT gyT vT2 25 kg m kg m 1.4310 Pa 1000 9.83 2 0m PT 1000 9.83 2 0.2m m s m s 5P 1.4110PaT1.41atm1 1P gy v P gy v2 22 2l argnarrowarg arg l e l e e narrow narrow5 kg m 1 kg m kg m 1 kg m 3.510 Pa 1000 9.8 3 2 0m 1000 1.3 P 1000 9.8 3 narrow 3 2 0m 1000 19 3 m s 2 m s m s 2 m s P2 51.710Pand1.7atm2Question 23Repeat the previous example with the following additional information: (a) thecross-sectional area of the hose at the top of the step is half that at the bottom ofthe step, and (b) the speed of the water at the bottom of the step is 1.20 m/s.From continuity equation: v T = 2(1.20m/s) = 2.40m/s1 2 1PB gyB vB PT gyT vT2 22PT PB g yB yT 1 2 vB vT225P 1.3910PaT1.39atm Question 24In designing a backyard water fountain, a gardener wants a stream of water to exitfrom the bottom of one can and land in a second one, as shown. The top of thesecond can is 0.500 m below the hole in the first can, which has water in it to adepth of 0.150 m. How far to the right of the first can must the second one beplaced to catch the stream of water?.How fast is thewater movingto the rightv 2gh m v 29.8 2 0.150m s mv 1.72sTime to hit bottom can1 2d at2t 2 .5m0.319s29.8 m/sDistancedx vxt m dx 1.72 0.319s s 0.549m12