1. Water flows at a rate of 25L/min through a horizontal 7.0cm diameter pipe und
ID: 251332 • Letter: 1
Question
1. Water flows at a rate of 25L/min through a horizontal 7.0cm diameter pipe under a pressure of 6.0Pa. At one point calcium deposits reduce the cross-sectional area of the pipe to 45cm^2. What is the pressure at this point?
2. A piece of copper tubing used in plumbing has a length of 54.0cm and an inner diameter of 1.25cm at 22 degrees celcius. When hot water at 95 degrees celcius flows throughthe tube, what are:
a) the tube's new length?
b) the change in its cross sectional-area?
c) Does the change in the cross-sectional area affect the flow speed? (Short paragraph to justify is required)
Explanation / Answer
Original area of crosssection of pipe=A1= 3.14 x (7/2)^2 =38.47cm2
now the cross sectional area=A2=45cm2
As the pressure is inversely proportional to surface area,
P1 x A1 = P2 x A2
6 x 38.47 =P2 x 45
230.82 = 45P2
P2 =230.82/4P2 = 5.12pa
Using 16.6 ×10^-6 as a linear coefficient of expansion,
54cm×16.6×10^-6/°C×(95°C-22°C) = .0654372cm
1.25cm×16.6×10^-6/°C×64°C = .001328 cm
At constant pressure velocity (flow rate) increases
due to increased area.
At constant volume flow rate is reduced with reduced area.
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