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nika2105 [10]
3 years ago
8

Two kilograms of air in a piston-cylinder assembly undergoes an isothermal process from an initial state of 200K, 300kPa to 600k

Pa. a) How much entropy is generated in the process, in kJ/K. b) Calculate the amount of lost work.
Engineering
1 answer:
Norma-Jean [14]3 years ago
4 0

Answer:

a) 0.39795 kJ/K

b) 79.589.37 kJ

Explanation:

m = Mass of air = 2 kg

Temperature = 200 K

P₁ = Initial pressure = 300 kPa

P₂ = Final pressure = 600 kPa

R = mass-specific gas constant for air = 287.058 J/kgK

a) For isentropic process

\Delta S=mRln\frac{P_1}{P_2}\\\Rightarrow \Delta S=2\times 287.058ln\frac{300}{600}\\\Rightarrow \Delta S=-397.95\ J/K

∴ Entropy is generated in the process is 0.39795 kJ/K

b)

W=mRTln\frac{P_1}{P_2}\\\Rightarrow W=2\times 287.058\times 200ln\frac{300}{600}\\\Rightarrow W=-79589.37\ J

∴ Amount of lost work is 79.589.37 kJ

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The correct statement about the lift and drag on an object is:_______
Lisa [10]

Answer:

(a). the resultant force in the direction of the freestream velocity is termed the drag and the resultant force normal to the freestream velocity is termed the lift

Explanation:

When a fluid flows around the surface of an object, it exerts a force on it. This force has two components, namely lift and drag.

The component of this force that is perpendicular (normal) to the freestream velocity is known as lift, while the component of this force that is parallel or in the direction of the fluid freestream flow is known as drag.

Lift is as a result of pressure differences, while drag results from forces due to pressure distributions over the object surface, and forces due to skin friction or viscous force.

Thus, drag results from the combination of pressure and viscous forces while lift results only from the<em> pressure differences</em> (not pressure forces as was used in option D).

The only correct option left is "A"

(a). the resultant force in the direction of the freestream velocity is termed the drag and the resultant force normal to the freestream velocity is termed the lift

8 0
3 years ago
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A lightweight electric car is powered by ten 12-V batteries. At a speed of 100 km/h, the average frictional force is 1500 N. Wha
Aleksandr [31]

Answer:41.67kW

Explanation: a) power = force * velocity

Convert km/hr to m/s=1000m/(60×60s)

=1000/3600

P=F×vel

Power =1500×100× 1000/3600

=1500×100×5/18

=41,666.67W

=41.67kW

6 0
3 years ago
Gas is kept in a 0.1 m diameter cylinder under the weight of a 100 kg piston that is held down by a spring with a stiffness k =
Artyom0805 [142]

Answer:

The spring is compressed by 0.275 meters.

Explanation:

For equilibrium of the gas and the piston the pressure exerted by the gas on the piston should be equal to the sum of  weight of the piston and the force the spring exerts on the piston

Mathematically we can write

Force_{pressure}=Force_{spring}+Weight_{piston}

we know that

Force_{pressure}=Pressure\times Area=300\times 10^{3}\times \frac{\pi \times 0.1^2}{4}=750\pi Newtons

Weight_{piston}=mass\times g=100\times 9.81=981Newtons

Now the force exerted by an spring compressed by a distance 'x' is given by Force_{spring}=k\cdot x=5\times 10^{3}\times x

Using the above quatities in the above relation we get

5\times 10^{3}\times x+981=750\pi \\\\\therefore x=\frac{750\pi -981}{5\times 10^{3}}=0.275meters

5 0
2 years ago
A standard penetration test has been conducted on a coarse sand at a depth of 16 ft below the ground surface. The blow counts ob
scoray [572]

Solution :

Given :

The number of blows is given as :

0 - 6 inch = 4 blows

6 - 12 inch = 6 blows

12 - 18 inch = 6 blows

The vertical effective stress $=1500 \ lb/ft^2$

                                              $= 71.82 \ kN/m^2$

                                             $ \sim 72 \ kN/m^2 $

Now,

$N_1=N_0 \left(\frac{350}{\bar{\sigma}+70} \right)$

$N_1 = $ corrected N - value of overburden

$\bar{\sigma}=$ effective stress at level of test

0 - 6 inch, $N_1=4 \left(\frac{350}{72+70} \right)$

                      = 9.86

6 - 12 inch, $N_1=6 \left(\frac{350}{72+70} \right) $

                        = 14.8

12 - 18 inch, $N_1=6 \left(\frac{350}{72+70} \right) $

                         = 14.8

$N_{avg}=\frac{9.86+14.8+14.8}{3}$

       = 13.14

       = 13

8 0
2 years ago
Natural Gas Corporation obtains a federal license to operate a gas pipeline through a certain area of Oregon. The Oregon state l
pentagon [3]

Answer:

b. the supremacy clause

Explanation:

This is clearly a violation of the supremacy clause of the constitution. The supremacy clause makes the constitution and federal laws made under the constitutional authority the supreme law of the united state. And in a case where there is a conflicting state law, as we have here with Oregon, the federal law is supposed to take priority.

So in this case where the federal law and the state law do not agree, the feral law has the power to override the law of the state. So oregon has violated the supremacy clause

6 0
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