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Verizon [17]
3 years ago
10

Calculate the rate at which body heat is conducted through the clothing of a skier in a steady- state process, given the followi

ng data: the body surface area is 1.80 m and the clothing is 1.00 cm thick; the skin surface temperature is 33.0 C and the outer surface of the clothing is at 1.00 C the thermal conductivity of the clothing is 0.040 W/m K
Engineering
1 answer:
olga2289 [7]3 years ago
4 0

Answer:

230.4W

Explanation:

Heat transfer by conduction consists of the transport of energy in the form of heat through solids, in this case a jacket.

the equation is as follows

Q=\frac{KA(T2-T1)}{L} \\

Where

Q=heat

k=conductivity=0.04

A=Area=1.8m^2

T2=33C

T1=1C

L=thickness=1cm=0.01mQ=\frac{(0.04)(1.8m^2)(33-1)}{0.01m}

Q=230.4W

the skier loses heat at the rate of 230.4W

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A train starts from rest at station A and accelerates at 0.6 m/s^2 for 60 s. Afterwards it travels with a constant velocity for
Aleks [24]

Answer:

The distance between the station A and B will be:

x_{A-B}=55.620\: km  

Explanation:

Let's find the distance that the train traveled during 60 seconds.

x_{1}=x_{0}+v_{0}t+0.5at^{2}

We know that starts from rest (v(0)=0) and the acceleration is 0.6 m/s², so the distance will be:

x_{1}=\frac{1}{2}(0.6)(60)^{2}

x_{1}=1080\: m

Now, we need to find the distance after 25 min at a constant speed. To get it, we need to find the speed at the end of the first distance.

v_{1}=v_{0}+at

v_{1}=(0.6)(60)=36\: m/s

Then the second distance will be:

x_{2}=v_{1}*1500

x_{2}=(36)(1500)=54000\: m        

The final distance is calculated whit the decelerate value:

v_{f}^{2}=v_{1}^{2}-2ax_{3}

The final velocity is zero because it rests at station B. The initial velocity will be v(1).

0=36^{2}-2(1.2)x_{3}

x_{3}=\frac{36^{2}}{2(1.2)}  

x_{3}=540\: m

Therefore, the distance between the station A and B will be:

x_{A-B}=x_{1}+x_{2}+x_{3}  

x_{A-B}=1080+54000+540=55.620\: km  

I hope it helps you!

 

7 0
2 years ago
Which contribution of Science is the most important discovery of man? Explain why?​
Vsevolod [243]

Answer:

<h2>The Invention of the Internal Combustion Engine (ICE)</h2>

Explanation:

The internal combustion engine is an engine in which ignition and combustion take place in the engine(in one place), the invention of the ICE was an integral part of the industrial revolution, as there was increasing demand for power, and manual labor could not suffice, especially during the mid 19 century.

The ICE made it possible for tasks that demand intensive power consumption to come through to reality, it was as a result of the invention of the ICE that road transportation was made easier for mankind, as the means of transport then was the use of beast of burden, now we have cars, airplanes ship, etc, essentially the invention of ICE reduced the tedious task man would have to engage in for his daily needs

5 0
3 years ago
You have removed a very large, thick plate of steel (AISI 1010) from your heat treat oven and have placed it on a large insulate
Andreas93 [3]

Answer:

for got sorry

Explanation:

6 0
3 years ago
A pump is used to extract water from a reservoir and deliver it to another reservoir whose free surface elevation is 200 ft abov
babunello [35]

Answer:

a) the expected flow rate is 31.4 ft³/s

b) the required brake horsepower is 2808.4 bhp

c) the location of pump inlet to avoid cavitation is -8.4 ft

Explanation:

Given the data in the question;

free surface elevation = 200 ft

total length of pipe required = 1000 ft

diameter = 12 inch

Iron with relative roughness ( k/D ) = 0.0005

H_{pump = 665-0.051Q² [Qinft ]

a) the expected flow rate

given that;

k/D  = 0.0005

k/2R = 0.0005

R/k = 1000

now, we determine the friction factor;

1/√f = 2log₁₀( R/k ) + 1.74

we substitute

1/√f = 2log₁₀( 1000 ) + 1.74

1/√f = 6 + 1.74

1/√f = 7.74

√f = 1/7.74

√f = 0.1291989

f = (0.1291989)²

f = 0.01669

Now, Using Bernoulli theorem between two reservoirs;

(p/ρq)₁ + (v²/2g)₁ + z₁ + H_p = (p/ρq)₂ + (v²/2g)₂ + z₂ + h_L

so

0 + 0 + 0 + 665-0.051Q² = 0 + 0 + 200 + flQ²/2gdA²

665-0.051Q² = 200 + flQ²/2gdA²

665-0.051Q² = 200 +[  ( 0.01669 × 1000 × Q² ) / (2 × 32.2 × (π/4)² × 1⁵ )

665 - 0.051Q² = 200 + [ 16.69Q² / 39.725 ]

665 - 200 - 0.051Q² = 0.420138Q²

665 - 200 = 0.420138Q² + 0.051Q²

465 = 0.471138Q²

Q² = 465 / 0.471138

Q² = 986.97196

Q = √986.97196

Q = 31.4 ft³/s

Therefore, the expected flow rate is 31.4 ft³/s

b) the brake horsepower required to drive the pump (assume an efficiency of 78%).

we know that;

P = ρgH_pQ / η

where; H_p = 665 - 0.051(986.97196) = 614.7

we substitute;

P = ( 62.42 × 614.7 × 31.4 ) / ( 0.78 × 550 )

P = 1204804.6236 / 429

P = 2808.4 bhp

Therefore, the required brake horsepower is 2808.4 bhp

c) the location of pump inlet to avoid cavitation (assume the required NPSH=25 ft).

NPSH = (P_{atom / ρg) - h_s - ( P_v / ρg )

we substitute

25  = ( 2116 / 62.42 ) - h_s - ( 30 / 62.42 )

h_s = 8.4 ft

Therefore, the location of pump inlet to avoid cavitation is -8.4 ft

6 0
2 years ago
Consider a junction that connects three pipes A, B and C. What can we say about the mass flow rates in each pipe for steady flow
Elis [28]

Answer:

The statement regarding the mass rate of flow is mathematically represented as follows \Rightarrow \rho \times Q_{3}=\rho \times Q_{1}+\rho \times Q_{2}

Explanation:

A junction of 3 pipes with indicated mass rates of flow is indicated in the attached figure

As a basic sense of intuition we know that the mass of the water that is in the pipe junction at any instant of time is conserved as the junction does not accumulate any mass.

The above statement can be mathematically written as

Mass_{Junction}=Constant\\\\\Rightarrow Mass_{in}=Mass_{out}

this is known as equation of conservation of mass / Equation of continuity.

Now we know that in a time 't' the volume that enter's the Junction 'O' is

1) From pipe 1 = V_{1}=Q_{1}\times t

1) From pipe 2 = V_{2}=Q_{2}\times t

Mass leaving the junction 'O' in the same time equals

From pipe 3 = V_{3}=Q_{3}\times t

From the basic relation of density, volume and mass we have

\rho =\frac{mass}{Volume}

Using the above relations in our basic equation of continuity we obtain

\rho \times V_{3}=\rho \times V_{1}+\rho \times V_{2}\\\\Q_{3}\times t=Q_{1}\times t+Q_{2}\times t\\\\\Rightarrow Q_{3}=Q_{1}+Q_{2}

Thus the mass flow rate equation becomes \Rightarrow \rho \times Q_{3}=\rho \times Q_{1}+\rho \times Q_{2}

6 0
3 years ago
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