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Test: Basic Concept - 3 - Mechanical Engineering MCQ


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15 Questions MCQ Test Thermodynamics - Test: Basic Concept - 3

Test: Basic Concept - 3 for Mechanical Engineering 2025 is part of Thermodynamics preparation. The Test: Basic Concept - 3 questions and answers have been prepared according to the Mechanical Engineering exam syllabus.The Test: Basic Concept - 3 MCQs are made for Mechanical Engineering 2025 Exam. Find important definitions, questions, notes, meanings, examples, exercises, MCQs and online tests for Test: Basic Concept - 3 below.
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Test: Basic Concept - 3 - Question 1

 The study of thermodynamics provides answer to the followings:
1. whether a process is feasible or not
2. to quantity the energy required for a process
3. rate or speed with which a process occurs
4. extent to which a reaction/process takes place

Which of the above statements are correct?

Detailed Solution for Test: Basic Concept - 3 - Question 1

The correct answer is 3: 1, 2, and 4.

1. The study of thermodynamics can determine whether a process is feasible or not. This is done by analyzing the energy changes and entropy changes associated with the process. If the energy change is positive (indicating energy input) and the entropy change is negative (indicating a decrease in disorder), the process may not be feasible.

2. Thermodynamics allows us to quantify the energy required for a process. By analyzing the energy changes (such as heat and work) associated with a reaction or process, we can determine the amount of energy needed for it to occur.

3. The study of thermodynamics does not directly provide information about the rate or speed with which a process occurs. However, it can provide insights into the factors that influence reaction rates, such as temperature and pressure. This is because the rate of a reaction is influenced by the energy changes involved (activation energy) and the thermodynamic properties of the reactants and products.

4. Thermodynamics also provides information about the extent to which a reaction or process takes place. This is typically determined by the concept of equilibrium, which is governed by the thermodynamic properties of the system. The equilibrium constant of a reaction is related to the extent to which reactants are converted into products at equilibrium.

Test: Basic Concept - 3 - Question 2

The volume and temperature of air (assumed to be an ideal gas) in a closed vessel is 2.87 m3 and 300 K, respectively. The gauge pressure indicated by a manometer fitted to the wall of the vessel is 0.5 bar. If the gas constant of air is R = 287 J/kg-K and the atmospheric pressure is 1 bar, the mass of air (in kg) in the vessel is

Detailed Solution for Test: Basic Concept - 3 - Question 2

We know that for an Ideal gas

PV = mRT

Also Pabs = Patm + Pg = 1 + 0.5        

= 1.5 bar = 150 kPa

Volume = 2.87 m3

R = 0.287 kPa

T = 300 K
Substituting the values, we get 1

150 × 2.87 = m × 0.287 × 300 m

= 5.00 kg

Hence, the correct option is (c).

Test: Basic Concept - 3 - Question 3

Consider the following statements:

1. Thermodynamic properties are the macroscopic coordinates significant only for systems existing in states of thermodynamic equilibrium.
2. Engineering thermodynamic studies about transfer and transformation of energy.
3. Engineering thermodynamics studies about storage, transfer and transformation of energy.

Which of the above is/are correct?

Detailed Solution for Test: Basic Concept - 3 - Question 3

Let's examine each statement:

  1. Thermodynamic properties are the macroscopic coordinates significant only for systems existing in states of thermodynamic equilibrium.
    This is correct. Thermodynamic properties, such as temperature, pressure, and volume, are macroscopic properties that describe the state of a system in equilibrium. These properties are well-defined only when the system is in thermodynamic equilibrium.

  2. Engineering thermodynamic studies about transfer and transformation of energy.
    This statement is partially correct, but it's not entirely comprehensive. Engineering thermodynamics does indeed focus on the transfer and transformation of energy, but it also encompasses other concepts, such as storage and the processes involved in the conversion of energy.

  3. Engineering thermodynamics studies about storage, transfer and transformation of energy.
    This is correct. Engineering thermodynamics is concerned with understanding and analyzing how energy is stored, transferred, and transformed, which is crucial for the design and operation of various engineering systems like engines, refrigerators, and power plants.

Thus, B: 1 and 3 is the correct answer as both statements 1 and 3 are accurate.

Test: Basic Concept - 3 - Question 4

An adiabatic boundary is one which

Detailed Solution for Test: Basic Concept - 3 - Question 4

An adiabatic boundary is one that prevents the transfer of heat between a system and its surroundings. In an adiabatic process, no heat is exchanged, although work can still be done on or by the system.

  • A: Prevents heat transfer is correct because adiabatic boundaries prevent heat exchange.
  • B: Permits heat transfer is incorrect because an adiabatic boundary blocks heat transfer.
  • C: Prevents work transfer is incorrect because an adiabatic boundary does not affect work transfer.
  • D: Permits work transfer is incorrect as it does not describe heat transfer but rather work, which is not restricted by the adiabatic boundary.

Thus, the correct answer is A: prevents heat transfer.

Test: Basic Concept - 3 - Question 5

Match the following List-I with List-ll:

List-I
A. Centrifugal fan
B. Control volume
C. Intensive property
D. Microscopic property

List-ll
1. Open system
2. Internal energy
3. Filling a tire at air station
4. Specific energy

Test: Basic Concept - 3 - Question 6

A certain amount of an ideal gas is initially at a pressure p1 and temperature T1. First, it undergoes a constant pressure process 1-2 such that T2 = 3T1/4. Then, it undergoes a constant volume process 2-3 such that T3 = T1/2. The ratio of the final volume to the initial volume of I the ideal gas is

Detailed Solution for Test: Basic Concept - 3 - Question 6

Let us draw process in p-v diagram

Process 1-2: Constant pressure

Process 2-3: Constant volume

Hence, the correct option is (b).

Test: Basic Concept - 3 - Question 7

 Match the following List-I (Thermometer) with  List -II ( Thermometric property)

Detailed Solution for Test: Basic Concept - 3 - Question 7

Test: Basic Concept - 3 - Question 8

 In a quasiequilibrium process, the pressure in a system

Detailed Solution for Test: Basic Concept - 3 - Question 8

In a quasiequilibrium process, the pressure in a system is constant at any given instant throughout the system. This is because a quasiequilibrium process is a thermodynamic process that occurs slowly enough for the system to remain in internal equilibrium. As the process progresses, the pressure across the system may change, but at any instant, it remains constant. 

*Answer can only contain numeric values
Test: Basic Concept - 3 - Question 9

Work is done on a adiabatic system due to which its velocity changes from 10 m/s to 20 m/s, elevation 
increases by 20 m and temperature increases by 1 K. The mass of the system is 10 kg, Cv = 100 J/(kg.K) and gravitational acceleration is 10 m/s2. If there is no change in any other component of the energy of the system, the magnitude of total work done (in kJ) on the system is 


Detailed Solution for Test: Basic Concept - 3 - Question 9

Given: C1 = 10 m/s, C2 = 20 m/s, z2 – z1 = 20 m,
T2 – T1 = 1 K
CV = 100 J/kg-K, g = 10 m/s2, δQ = 0

Assuming compressible fluid with γ = 1

SFEE:

On the system, δ W = 4.5 kJ

Hence, the correct answer is 4.5.

Test: Basic Concept - 3 - Question 10

Convert the following readings of pressure to kPa, assuming that the barometer reads 760mm of Hg and match  the List-I and List-II

Detailed Solution for Test: Basic Concept - 3 - Question 10

50 cm Hg vacuume:

80 cm Hg gauge:

1.2 m of H20 guage:

Test: Basic Concept - 3 - Question 11

Match the List-I (Terms) with List-ll (Description) and select the correct answer:

List-I
A. Change of state
B. Path
C. Process

List-ll
1. Succession of states
2. One or more properties changes
3. Change of state for specified path

Detailed Solution for Test: Basic Concept - 3 - Question 11

Properties are the coordinates to describe the state of a system. They are state variables of the system. Any operation in which one or more of the properties of a system changes is called a change of state. The succession of states passes through during a change of state is called the path of the change of state is called a process. A thermodynamic cycle is defined as a series of state changes such that the final state is identical with the initial state.

Test: Basic Concept - 3 - Question 12

Ice kept in a wail insulated thermo-flask is an example of which system?

Detailed Solution for Test: Basic Concept - 3 - Question 12

The ice in a well-insulated thermos flask represents a specific type of thermodynamic system. This can be understood through the following points:

  • A closed system is one where matter cannot enter or leave, but energy can be exchanged. In this case, the ice does not gain or lose mass, but heat can transfer between the ice and its surroundings.
  • In an isolated system, neither matter nor energy can enter or leave. While the thermos minimizes heat transfer, it may not be perfectly isolated.
  • An open system allows both matter and energy to flow in and out. The thermos does not fall into this category as it does not permit the entry or exit of ice.
  • A non-flow adiabatic system refers to a system where no heat flows in or out, typically under constant conditions. This might be a characteristic of the thermos, but generally, it is not commonly used to define the situation.

Thus, while the thermos is designed to be efficient in maintaining the temperature of the ice, the most accurate classification is that of a closed system.

Test: Basic Concept - 3 - Question 13

For an isolated system executing a process
1. no heat transfer takes place
2. no work is done
3. no mass crosses the boundary
4. no chemical reaction takes place within the system

Which of the above statement are correct?

Detailed Solution for Test: Basic Concept - 3 - Question 13

For an isolated system executing a process:

  • No heat transfer takes place.
  • No work is done.
  • No mass crosses the boundary.
  • No chemical reaction occurs within the system.

In an isolated system, the following conditions are crucial:

  • The system does not exchange energy with its surroundings.
  • It maintains a constant mass throughout the process.
  • Internal reactions do not affect the overall energy state.

Therefore, the correct statements regarding the characteristics of an isolated system are:

  • Heat transfer is absent.
  • No work is performed on or by the system.
  • Mass remains unchanged, and no chemical interactions occur.

Thus, the accurate combination of statements is the first three: 1, 2, and 3.

Test: Basic Concept - 3 - Question 14

A body of weight 100 N falls freely a vertical distance of 50 m. The atmospheric drag force is 0.5 N. For the body, the work interaction is

Detailed Solution for Test: Basic Concept - 3 - Question 14

Net work done = 

Work interaction or work done at boundary of system is only by drag force

W = −Fd × s = −0.5 × 50 = −25 J

This is work done by surrounding air on system and is negative. Hence, positive work is done by body on surrounding air and is equal to 25 J.
Hence, the correct option is (d).

Test: Basic Concept - 3 - Question 15

Comprehension
A football was inflated to a gauge pressure of 1 bar when the ambient temperature was 15°C. When the game started next day, the air temperature at the stadium was 5°C. Assume that the volume of the football remains constant at 2500 cm3.
Gauge pressure of air to which the ball must have been originally inflated so that it would equal 1 bar gauge at the stadium is

Detailed Solution for Test: Basic Concept - 3 - Question 15

Step-by-Step Solution

  1. Understand the Relationship Between Pressure and Temperature:
    • For a gas at constant volume, the pressure and temperature are related by the formula:
      P₁ / T₁ = P₂ / T₂
    • Here, P represents absolute pressure and T represents temperature in Kelvin.
  2. Convert Temperatures to Kelvin:
    • T₁ (Initial Temperature) = 15°C + 273 = 288 K
    • T₂ (Final Temperature) = 5°C + 273 = 278 K
  3. Determine Absolute Pressures:
    • Gauge Pressure is the pressure above atmospheric pressure.
    • Assume atmospheric pressure P_atm = 1 bar.
    • Final Absolute Pressure P₂_abs = Gauge Pressure + Atmospheric Pressure = 1 bar + 1 bar = 2 bar
  4. Apply the Pressure-Temperature Relationship:
    • Using the formula: P₁_abs / T₁ = P₂_abs / T₂
    • Substitute the known values:
      P₁_abs = (P₂_abs × T₁) / T₂ = (2 bar × 288 K) / 278 K ≈ 2.07 bar
  5. Calculate the Original Gauge Pressure:
    • Gauge Pressure P₁_gauge = Absolute Pressure - Atmospheric Pressure
    • P₁_gauge = 2.07 bar - 1 bar = 1.07 bar

Conclusion

The original gauge pressure to which the football must have been inflated is 1.07 bar. Therefore, the correct answer is:

Option c) 1.07 bar

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