PHYSICS COLLEGE

A piston-cylinder device contains 5 kg of refrigerant-134a at 0.7 MPa and 60°C. The refrigerant is now cooled at constant pressure until it exists as a liquid at 24°C. If the surroundings are at 100 kPa and-24°C, determine: (a) the exergy of the refrigerant at the initial and the final states and
(b) the exergy destroyed during this process.

Answers

Answer 1

Answer:

A) The exergy of the refrigerant at the initial and final states are :

Initial state = - 135.5285 kJ
Final state = -51.96 kJ

B) The exergy destroyed during this process is : - 1048.4397 kJ

Given data :

Mass ( M ) = 5 kg

P1 = 0.7 Mpa = P2

T1 = 60°C = 333 k

To = 24°C = 297 k

P2 = 100 kPa

A) Determine the exergy at initial and final states

At initial state :

U = 274.01 kJ/Kg , V = 0.034875 m³/kg , S = 1.0256 KJ/kg.k

exergy ( Ф ) at initial state = M ( U + P₂V - T₀S )

= 5 ( 274.01 + 100* 10³ * 0.034875 - 297 * 1.0256)

≈ - 135.5285 kJ

At final state :

U = 84.44 kJ / kg , V = 0.0008261 m³/kg, S = 0.31958 kJ/kg.k

exergy ( ( Ф ) at final state = M ( U + P₂V - T₀S )

= -51.96 kJ

B) Determine the exergy destroyed

exergy destroyed = To * M ( S2 - S1 )

= 297 * 5 ( 0.31958 - 1.0256 )

= - 1048.4397 KJ

Hence we can conclude that A) The exergy of the refrigerant at the initial and final states are : Initial state = - 135.5285 kJ, Final state = -51.96 kJ and The exergy destroyed during this process is : - 1048.4397 kJ

Learn more about exergy : brainly.com/question/25534266

Answer 2

Answer:

Final answer:

Exergy of refrigerant-134a at initial and final states is obtained from property tables and by multiplying the mass of the refrigerant with its specific exergy at each state. The difference in exergy between the two states represents the exergy destroyed.

Explanation:

To solve the given question, we need the property values of

refrigerant-134a

at the initial and the final states.

At an initial state of 0.7 MPa and 60°C, the specific exergy for refrigerant-134a can be obtained from property tables which are standard in thermodynamics textbooks. Same for the final state at 0.7 MPa and 24°C, the specific exergy can be obtained from the same property tables.

The exergy of the refrigerant at the initial and the final states can be calculated by multiplying the mass of the refrigerant with its specific exergy at each state.

Exergy destruction during this process can be calculated using the relation between exergy change and exergy destruction. The exergy change of a system between initial and final states is equal to the difference of the exergy of the system at final and initial states.

Based on the second law of thermodynamics, the difference in exergy should be equal to the exergy destroyed during the process.

Learn more about Exergy of Refrigerant here:

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Explain how the Doppler effect works for sound waves and give some familiar examples.

Answers

Answer and Explanation:

Doppler effect : According to Doppler effect whenever there is a relative motion between the source and observer then there is an increase or decrease in frequency of sound light or waves.

REASON OF DOPPLER EFFECT : Doppler effect is mainly due to the sudden change in pitch of the sound

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A 79-turn, 16.035-cm-diameter coil is at rest in a horizontal plane. A uniform magnetic field 43 degrees away from vertical increases from 0.997 T to 6.683 T in 56.691 s. Determine the emf induced in the coil.

Answers

Answer:

The induced emf is 0.0888 V.

Explanation:

Given that,

Number of turns = 79

Diameter = 16.035 cm

Angle = 43

Change in magnetic field $\Delta B=(6.683-0.997)= 5.686\ T$

Time = 56.691 s

We need to calculate the induced emf

Using formula of induced emf

$\epsilon=(NA\Delta B\cos\theta)/(\Delta T)$

Where, N = number of turns

A = area

B = magnetic field

Put the value into the formula

$\epsilon=(79*\pi*(8.0175*10^(-2))^2*5.686*\cos43)/(56.691)$

$\epsilon =0.0888\ V$

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When running a 100 meter race Wyatt reaches his maximum speed when he is 40 meters from the starting line, and 7 seconds have elapsed since the start of the race. Wyatt continues at this max speed for the rest of the race and is 85 meters from the starting line 12 seconds after the start of the race. What is Wyatt's max speed

Answers

Answer:

9 m/s

Explanation:

Wyatt maintains the maximum speed for the rest of the race. This motion begins when his displacement is 40 m and the time is 7 s. At time 12 s, his displacement is 85 m. Because this motion is constant-velocity, the maximum speed is given by

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A research Van de Graaff generator has a 2.00-m diameter metal sphere with a charge of 5.00 mC on it. (a) What is the potential near its surface?
(b) At what distance from its center is the potential 1.00 MV?
(c) An oxygen atom with three missing electrons is released near the Van de Graaff generator. What is its energy in MeV when the atom is at the distance found in part b?

Answers

Answer:

a) $V=49.5MV$

b) $r=49.5m$

c) $\Delta U=3*(49.5-1)=145.5 MeV$

Explanation:

a) The potential equation is given by:

$V=k(Q)/(r)$

k is the electrostatic constant ( $k=9.9*10^(9)Nm^(2)/C^(2)$ )

Q is the charge Q = 5mC

r is the radius of the sphere r = 1 m

$V=9.9*10^(9)(5*10^(-3))/(1)=49.5MV$

b) We solve it using the same equation.

Here we need to find r:

$r=k(Q)/(V)$

$r=9.9*10^(9)(5*10^(-3))/(1*10^(6))$

$r=49.5m$

c) The relation between difference potential and electrical energy is:

$\Delta U=\Delta Vq$

here q is 3e becuase oxygen atom has three missing electrons

Therefore:

$\Delta U=3*(49.5-1)=145.5 MeV$

I hope it heps you!

Which is true about inelastic collisions: a. An inelastic collision does not obey conservation of energy. b. An inelastic collision conserves kinetic energy. c. Objects will stick together upon collision. d. Momentum is not conserved in inelastic collisions..

Answers

Answer:

Option c is correct

Explanation:

There are two types of collisions-elastic collision and inelastic collision.

In elastic collision, both kinetic energy and total momentum are conserved. On the other hand, in inelastic collision, total momentum is conserved but kinetic energy is not conserved. Thus, option b and d are incorrect.

Total energy is always conserved in both types. Thus, option a is incorrect.

In a perfectly inelastic collision, objects stick together. This happens because maximum kinetic energy is dissipated and used in bonding of the two objects. Thus, correct option is c.

Answer:

i believe its a?

Explanation:

In an inelastic collision, momentum is conserved

I'm a little bit unsure about this question.

Answers

Answer:

Option C. 4 Hz

Explanation:

To know the correct answer to the question given above, it is important we know the definition of frequency.

Frequency can simply be defined as the number of complete oscillations or circles made in one second.

Considering the diagram given above, the wave passes through the medium over a period of one second.

Thus, we can obtain the frequency by simply counting the numbers of complete circles made during the period.

From the diagram given above,

The number of circles = 4

Thus,

The frequency is 4 Hz

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