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3 years ago

For a refrigerator, COP<1 a) True b) False

Engineering

1 answer:

WINSTONCH [101]3 years ago

4 0

Answer:

False

Explanation:

COP is Coeficient of performance, it relates useful heat moved with work consumed, it is used in refrigerators and heat pumps.

For refrigerators the useful heat is the one extracted from the cold reservoir. Therefore:

$COP = \frac{Tcold}{T.hot - Tcold}$

This often exceeds 1.

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May you tell me the meaning of "Tolerance is a bitter tree, but its fruit is sweet "by Aristotle

trapecia [35]

Answer:

“Patience is bitter, but its fruit is sweet. With patience you can bear up under any adversity and survive any defeat. With patience you can control your destiny and have what you will. Patience is the key to contentment, for you and for those who must live with you. To be brave without patience can kill you.

Explanation:

Aristotle’s Ethical Doctrine of the Mean. According to Aristotle’s ethical rule about the Golden Mean, to use a thing with virtue is a kind of moderation, as it leads the particular thing being in a good condition, and allows for its functions to be performed in a proper manner.

7 0

3 years ago

/ Air enters a 20-cm-diameter 12-m-long underwater duct at 50°C and 1 atm at a

Digiron [165]

Answer:

A) EXIT TEMPERATURE = 14⁰C

b) rate of heat transfer of air = - 13475.78 = - 13.5 kw

Explanation:

Given data :

diameter of duct = 20-cm = 0.2 m

length of duct = 12-m

temperature of air at inlet= 50⁰c

pressure = 1 atm

mean velocity = 7 m/s

average heat transfer coefficient = 85 w/m^2⁰c

water temperature = 5⁰c

surface temperature ( Ts) = 5⁰c

properties of air at 50⁰c and at 1 atm

= 1.092 kg/m^3

Cp = 1007 j/kg⁰c

k = 0.02735 W/m⁰c

Pr = 0.7228

v = 1.798 * 10^-5 m^2/s

determine the exit temperature of air and the rate of heat transfer

attached below is the detailed solution

Calculate the mass flow rate

= p*Ac*Vmean

= 1.092 * 0.0314 * 7 = 0.24 kg/s

4 0

3 years ago

An organization is struggling to differentiate threats from normal traffic and access to systems. A security engineer has been a

AnnZ [28]

Answer:

Web application Firewall (WAF)

Explanation:

The Web application Firewall (WAF) will be recommended. This will enormously help any organisation that is having a struggle of differentiating threats from normal traffic and access to systems.

WAF is also going to It aggregate data and provide metrics that will assist in identifying malicious actors. Another vital function of WAF will be to block unwanted web traffic from accessing your site. It will protect against hacks, brute force attacks, DDoS attacks, cross-site scripting, SQL injection, and zero-day exploits.

8 0

4 years ago

You want to plate a steel part having a surface area of 160 with a 0.002--thick layer of lead. The atomic mass of lead is 207.19

Pepsi [2]

Answer:

To answer this question we assumed that the area units and the thickness units are given in inches.

The number of atoms of lead required is 1.73x10²³.

Explanation:

To find the number of atoms of lead we need to find first the volume of the plate:

$V = A*t$

Where:

A: is the surface area = 160

t: is the thickness = 0.002

Assuming that the units given above are in inches we proceed to calculate the volume:

$V = A*t = 160 in^{2}*0.002 in = 0.32 in^{3}*(\frac{2.54 cm}{1 in})^{3} = 5.24 cm^{3}$

Now, using the density we can find the mass:

$m = d*V = 11.36 g/cm^{3}*5.24 cm^{3} = 59.5 g$

Finally, with the Avogadros number ( $N_{A}$ ) and with the atomic mass (A) we can find the number of atoms (N):

$N = \frac{m*N_{A}}{A} = \frac{59.5 g*6.022 \cdot 10^{23} atoms/mol}{207.19 g/mol} = 1.73 \cdot 10^{23} atoms$

Hence, the number of atoms of lead required is 1.73x10²³.

I hope it helps you!

3 0

3 years ago

It is said that Archimedes discovered the buoyancy laws when asked by King Hiero of Syracuse to determine whether his new crown

sertanlavr [38]

Answer with Explanation:

The crown will be pure if it's specific gravity is 19.3

Now by definition of specific gravity it is the ratio between the weight of an object to the weight of water of equal volume

Since it is given that the weight of the crown is 11.8 N we need to find it's volume

Now According to Archimedes principle when the crown is immersed into water the water shall exert a force in upwards direction on the crown with a magnitude equaling to weight of the water displaced by the crown

Mathematically this is the difference between the weight of the crown in air and weight when immersed in water

Thus Buoyant force is $F_{B}=11.8-10.9=0.9N$

Now by Archimedes principle This force equals in magnitude to the weight of water of same volume as of the crown

Thus the specific gravity of the crown equals

$S.G=\frac{11.8}{0.9}=13.11$

As we see that the specific gravity of the crown material is less than that of pure gold hence we conclude that it is impure.

4 0

4 years ago