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iren [92.7K]
2 years ago
13

during a cold winter day, wind at 42 km/h is blowing parallel to a 6-m-high and 10-m-high wall of a house. If the air outside is

at 5 degrees C and the surface temperature of the wall is 12 degrees C, determine the rate of heat loss from that wall by convection. What would your answer be if the wind velocity was doubled?

Physics
1 answer:
Arturiano [62]2 years ago
4 0

Answer: 9.08KW and 16.21KW

Explanation:

The convection over a flat surface with a length of 10 m and a width of 6m.

The mean temperature is (5oC + 12oC)/2 = 8.5oC.

Then find the following properties of air at this temperature from Table A-15:

k = 0.02428 W/m(oC, v= 1.413x10-5 m2/s, and Pr = 0.7340.

find the Reynolds number. Re= VL/v

Check screenshot

This means that the flow becomes turbulent over the plate and we can use the Nusselt number equation for combined laminar and turbulent flow.

Check screenshot

We then use this Nusselt number to find the heat transfer coefficient and the heat transfer.

Check the screen shot for the calculation

Ans

9.08 kW

Then if the wind velocity were doubled, the Re number would be doubled and we would repeat the calculations above, starting with this revised Reynolds number..

Ans

16.21 kW

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Luda [366]

Answer

The answer and procedures of the exercise are attached in the following archives.

Step-by-step explanation:

You will find the procedures, formulas or necessary explanations in the archive attached below. If you have any question ask and I will aclare your doubts kindly.  

7 0
2 years ago
wheel rotates from rest with constant angular acceleration. Part A If it rotates through 8.00 revolutions in the first 2.50 s, h
Alex73 [517]

Answer:

x2 = 64 revolutions.

it rotate through 64 revolutions in the next 5.00 s

Explanation:

Given;

wheel rotates from rest with constant angular acceleration.

Initial angular speed v = 0

Time t = 2.50

Distance x = 8 rev

Applying equation of motion;

x = vt +0.5at^2 ........1

Since v = 0

x = 0.5at^2

making a the subject of formula;

a = x/0.5t^2 = 2x/t^2

a = angular acceleration

t = time taken

x = angular distance

Substituting the values;

a = 2(8)/2.5^2

a = 2.56 rev/s^2

velocity at t = 2.50

v1 = a×t = 2.56×2.50 = 6.4 rev/s

Through the next 5 second;

t2 = 5 seconds

a2 = 2.56 rev/s^2

v2 = 6.4 rev/s

From equation 1;

x = vt +0.5at^2

Substituting the values;

x2 = 6.4(5) + 0.5×2.56×5^2

x2 = 64 revolutions.

it rotate through 64 revolutions in the next 5.00 s

5 0
2 years ago
A ball, which has a mass of 1.25 kg, is thrown straight up from the top of a building 225 meters tall with a velocity of 52.0 m/
Elena-2011 [213]

First we will find the speed of the ball just before it will hit the floor

so in order to find the speed of the cart we will first use energy conservation

KE_i + PE_i = KE_f + PE_f

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\frac{1}{2}(1.25)(52)^2 + 1.25(9.8)(225) = \frac{1}{2}(1.25)v_f^2

So by solving above equation we will have

v_f = 84.3 m/s

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P = mv

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6 0
2 years ago
Consider the following:
pychu [463]

Answer:

They have different wavelengths.

They have different frequencies.

They propagate at different speeds through non-vacuum media depending on both their frequency and the material in which they travel.

Explanation:

The complete question is

Consider the following:

a) radio waves emitted by a weather radar system to detect raindrops and ice crystals in the atmosphere to study weather patterns;

b) microwaves used in communication satellite transmissions;

c) infrared waves that are perceived as heat when you turn on a burner on an electric stove;

d) the multicolor light in a rainbow;

e) the ultraviolet solar radiation that reaches the surface of the earth and causes unprotected skin to burn; and

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check all that apply to the above

They have different wavelengths.

They have different frequencies.

They propagate at different speeds through a vacuum depending on their frequency.

They propagate at different speeds through non-vacuum media depending on both their frequency and the material in which they travel.

They require different media to propagate.

All the above phenomena are due the electromagnetic wave spectrum. Electromagnetic waves travel at a constant speed of 3 x 10^8 m/s in a vacuum. Within the spectrum, the different types of electromagnetic waves exists in different band range of frequencies and wavelengths unique to each of the waves, and the energy they carry. When these waves enter a non-vacuum medium, their speed change, depending on the nature of the material of the medium, and the frequency or the wavelength of the incoming wave.

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A squeeze bottle squeezes when pressed. It regains its shape when pressed .It regains its shape when the pressure from your hand
Leokris [45]

Answer:

The squeeze will not regain its shape

Explanation:

The squeeze bottle will not regain its shape.

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So, the squeeze bottle does not regain its shape due to this imbalance of pressure.

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