Question

The water is flowing through a pipe having diameters 20 cm and 10 cm
at section 1 and 2 respectively. The rate of flow through pipe is 35
litres/s The section 1 is 6 m above datum and section 2 is 4 m above
datum If the pressure at section 1 is 30. 24 N/cm2, find the intensity of
pressure at section 2​

Answer 1

The value of pressure at section 2 is P2 = 40.27 N/cm^2

Explanation:

We are gievn thta:

• D1 = 20 cm = 20 x 10^-2 m = 0.2 m
• D2 = 10 cm = 10 x10^-2 m = 0.1 m
• Q = 35 L / s = 35 / 1000 = 0.035 m^2 / sec
• P1 = 39.24 N/cm^2
• h1 = 6 m
• h2 = 4 m

Solution:

Now A1 = π / 4(D1)^2 = 3.14 / 4 x (0.2)^2 = 0.0314 m^2

A2 =  π / 4(D2)^2 = 3.14 / 4 x (0.1)^2 = 0.0785 m^2

Q = A1V1 = A2V2

V1 = Q / A1 = 0.035 / 0.0314

V1 = 1.11 m/s

V 2 = Q / A2 = 0.035 / 0.0785 = 4.456 m/s

Using Bernouli's equation:

P1 / ρg + V1^2 / 2g + h1 = P2 / ρg + V2^2 / 2g + h2

After putting the values we get;

P2 / 9810 = 46.063 - 5.012 = 41.051

P2 = 40.27 N/cm^2

Answer 2

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