Water circulates throughout a house in a hot water heating system. If the water is pumped at a speed of 0.50m/s through a 4.0-cm diameter pipe in the basement under a pressure of 3.03x10^5 Pa, what will be the velocity and pressure in a 2.6-cm diameter pipe on the second floor 5.0m above?

Respuesta :

Answer:

velocity and pressure in a 2.6-cm:

P2 = 2.53x10^5Pa, v2 = 1.18m/s

Explanation:

Pressure = P, Velocity = v, Height = h, Diameter = d, Radius= r, Area = A

Area = πr^2

From the question:

v1 = 0.5m/s

d1 = 4cm = 0.04m

r1 = d1/2 = 0.04/2 = 0.02m

Since water was pumped from basement, h1 = 0m

P1 = 3.03x10^5 Pa

A1 = π×0.02×0.02

A1 = 0.0004πm^2

v2 = unknown

d2 = 2.6cm = 0.026m

r2 = d2/2 = 0.026/2 = 0.013m

h2 = 5m

P2 = unknown

A2 = π×0.013×0.013

A2 = 0.000169πm^2

Using continuity equation:

A1v1 = A2v2

0.0004π * 0.5 = 0.000169π * v2

v2 = (0.0004π * 0.5)/(0.000169π)

v2 = 1.18m/s

Applying a Bernoulli principle

P + 1/2*density*v^2 + density*g*h =C

C = constant

P1 + 1/2*density*v1^2 + density*g*h1

= P2 + 1/2*density*v2^2 + density*g*h2

Let g = 9.81m/s

density of water = 1000kg/m^3

(P1-P2) = 1/2* density(v2^2 - v1^2) +(density*g*h2) - (density*g*h1)

(P1-P2) = 1/2* density(v2^2 - v1^2) +

density* g(h2-h1)

(3.03x10^5 - P2)= 1/2*1000 (1.18^2-0.5^2) + 1000(9.81(5-0))

(3.03x10^5 - P2) = 500(1.3924-0.25) + 49050

3.03x10^5 - P2 = 571.2 + 49050

3.03x10^5 - P2 = 49621.2

3.03x10^5 - 49621.2 = P2

P2 = 253378.8

P2 = 2.53x10^5Pa

P2 = 2.53x10^5Pa, v2 = 1.18m/s

The velocity and pressure in a 2.6-cm diameter pipe on the second floor 5.0m above are 1.18m/s and  2.51 * 10^5 Pa

The given parameters are:

  • Initial velocity: [tex]v_1 = 0.5ms^{-1}[/tex]
  • Initial diameter  [tex]d_1 = 4cm[/tex]
  • Initial pressure: [tex]P_1 = 3.03 \times 10^5 Pa[/tex]

Start by calculating the radius using:

[tex]r = 0.5d[/tex]

So, we have:

[tex]r_1 = 0.5 \times 4cm[/tex]

[tex]r_1 = 2cm[/tex]

Express as meters

[tex]r_1 = 0.02m[/tex]

Next, calculate the area using:

[tex]A =\pi r^2[/tex]

So, we have:

[tex]A_1 = \pi \times 0.02^2[/tex]

[tex]A_1 = \pi \times 0.004[/tex]

[tex]A_1 = 0.004\pi[/tex]

Also from the question, we have:

[tex]d_2 = 2.6cm[/tex]

[tex]h = 5m[/tex]

Calculate the radius using:

[tex]r = 0.5d[/tex]

So, we have:

[tex]r_2 = 0.5 \times 2.6cm[/tex]

[tex]r_2 = 1.3cm[/tex]

Express as meters

[tex]r_2 = 0.013m[/tex]

The area is then calculated as:

[tex]A =\pi r^2[/tex]

So, we have:

[tex]A_2 = \pi \times 0.013^2[/tex]

[tex]A_2 = \pi \times 0.000169[/tex]

[tex]A_2 = 0.000169\pi[/tex]

The velocity is then calculated using:

[tex]A_1v_1 = A_2v_2[/tex]

Make v2 the subject

[tex]v_2 = \frac{A_1v_1}{A_2}[/tex]

So, we have:

[tex]v_2 = \frac{0.0004\pi \times 0.5}{0.000169\pi}[/tex]

[tex]v_2 = \frac{0.0004\times 0.5}{0.000169}[/tex]

[tex]v_2 = 1.18343195266[/tex]

Approximate

[tex]v_2 = 1.18[/tex]

The pressure is then calculated as follows:

[tex]P_1 + 0.5 \times density \times v_1^2 + density \times g \times h_1 = P_2 + 0.5 \times density \times v_2^2 + density \times g \times h_2[/tex]

Where:

[tex]g = 9.81ms^{-1}[/tex]

[tex]density = 1000kgm^{-3[/tex]

[tex]h_1 = 0[/tex]

So, we have:

[tex]3 \times 10^5 + 0.5 \times 1000 \times 0.5^2 + 1000 \times 9.8 \times 0 = P_2 + 0.5 \times 1000 \times 1.18^2 + 1000 \times 9.8 \times 5[/tex]

[tex]300000 + 125 + 0 = P_2 + 696.2 + 49000[/tex]

Collect like terms

[tex]300000 + 125 - 696.2 - 49000 = P_2[/tex]

[tex]250428.8 = P_2[/tex]

Rewrite as:

[tex]P_2 =250428.8[/tex]

Rewrite as:

[tex]P_2 = 2.51 \times 10^5\ Pa[/tex]

Hence, the velocity and pressure are 1.18m/s and  2.51 * 10^5 Pa

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