Water at 20°C flows through a horizontal garden hose at the rate of 4.8 10-4 m3/
ID: 249880 • Letter: W
Question
Water at 20°C flows through a horizontal garden hose at the rate of 4.8 10-4 m3/2. The diameter of the garden hose is 2.0 cm. (a) What is the water speed in the hose? 1.53 Correct: Your answer is correct. m/s (b) What is the pressure drop across a 20.-m length of hose? kPa (c) By what factor does the water speed change if the cross-sectional area of the hose is halved, but the length and pressure drop remain the same? (d) By what factor does the volume flow rate change if the cross-sectional area of the hose is halved, but the length and pressure drop remain the same? Explain.
Explanation / Answer
a) Q = Av
Q= 4.8 10-4 m3/2
A= 3.14*2*2*10^-4 m^2
we get V= 1.53m/sec
b) pressure drop
P = 0kPa
since the hose is horizontal and there is no change in velocity so pressure drop is zero
P = density * g * ( vertical distance)
P = 0kPa
c) from continuity equation
A1 V1 = A2V2
A2 = A1/2
therefore
V2 = 2V1 ( answer 2 )
d) since incoming mass = outgoing mass
and density is not varying
therefore
inflovolume = outflowvolume
Q dooesnot change
Q = 4.8 10-4 m3/2
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