Deck 9: Thermal Physics

Question 1

An athlete doing push-ups performs 700 kJ of work and loses 455 kJ of heat. What is the change in the internal energy of the athlete?

A)1155 kJ
B)245 kJ
C)-245 kJ
D)-1155 kJ

Answer 1

-1155 kJ

Question 2

How is the molar heat capacity C of a substance of molar mass M related to the specific heat capacity c?

A)C = nc, where n = number of moles
B)c = nC, where n = number of moles
C)c = MC
D)C = Mc

Answer 2

C = Mc

Question 3

An iron bullet of mass 100 g and travelling at 500 m/s hits a fixed iron plate of mass 400G) Assume the bullet is brought to rest on hitting the plate.What temperature rise occurs in the iron, assuming the temperature distribution is uniform?

A)70°C
B)56°C
C)7°C
D)6°C

Answer 3

56°C

Question 4

In comparing adiabatic and isothermal compressions of a gas from the same initial pressure and volume, in which one of the following ways do you expect the pressure to behave differently between the two processes?

A)The pressures remain equal to each other during compression.
B)The pressure climbs more rapidly for adiabatic compression.
C)More heat is available to raise the pressure in adiabatic compression than in isothermal compression.
D)The pressure climbs more rapidly for isothermal compression.

Question 5

What happens during an isochoric process when the temperature of a gas is increased by a factor of 10%?

A)The volume increases by 10%.
B)The pressure increases by 10%.
C)Both volume and pressure increase.
D)Pressure increases by less than 10%, with the balance contributing to expansion of the gas.

Question 6

An athlete doing push-ups performs 700 kJ of work and loses 450 kJ of heat. What is the change in the internal energy of the athlete?

A)1150 kJ
B)250 kJ
C)-250 kJ
D)-1150 kJ

Question 7

An ideal monatomic gas expands at a constant pressure of 120 kPa from an initial volume of 2.0 L to a final volume of 5.0 L. If the temperature of the gas remains constant, how much heat flows into the gas?

A)360 J
B)-360 J
C)3.6 kJ
D)-3 kJ

Question 8

Figure 9.1 p-V diagram of several possible thermodynamic processes between initial and final states.
In Fig. 9.1, by which closed path, starting and ending at "initial" and passing through "final," will the most work be done on the gas?

A)(iii) followed by reverse of (i)
B)(iii) followed by reverse of (ii)
C)(i) followed by reverse of (iii)
D)(ii) followed by reverse of (i)

Question 9

A monatomic ideal gas with an initial pressure of 100 kPa and an initial volume of 1.50 L expands isothermally to a final volume of 5.00 L. How much work is done on the gas in this process?

A)181 J
B)78 J
C)-78 J
D)-181 J

Question 10

An expandable container holds 2.50 moles of He gas with an initial pressure of 750 kPa and an initial volume of 2.0 L. The gas expands isothermally to a final pressure of 375 kPa. How much heat is gained by the gas in this process?

A)1040 J
B)452 J
C)-452 J
D)-1040 J

Question 11

A gas expands from an initial volume of 0.015 m³ to a final volume of 0.075 m³, while its pressure increases linearly with the volume (so that the process follows a straight-line path in a p-V diagram) from 80 kPa to 275 kPa. How much work is done by the system?

A)-10.6 kJ
B)-5.6 kJ
C)5.6 kJ
D)10.6 kJ

Question 12

2.0 moles of an ideal monatomic gas are initially at a temperature of 300 K. If the gas gains 2800 J of heat and performs 400 J of work, what is its final temperature?

A)515 K
B)396 K
C)251 K
D)204 K

Question 13

Figure 9.1 p-V diagram of several possible thermodynamic processes between initial and final states.
A fixed mass of gas initially occupies a 2 L volume at atmospheric pressure. It undergoes an isobaric change to a volume of 5 L, followed by an isochoric change to a pressure of 2 atm. See path (iii) in Fig. 9.1. If the system is brought back to its initial state along the reverse of path (ii), what is the net work done on the gas?

A)-456 J
B)-152 J
C)152 J
D)456 J

Question 14

Which of the following statements best describes the characteristics of gauge pressure?

A)Gauge pressure is always positive.
B)When absolute pressure is lower than atmospheric pressure, the gauge pressure is positive.
C)Gauge pressure depends on atmospheric pressure.
D)Positive gauge pressure gives a system the propensity to expand.

Question 15

A gas expands from an initial volume of 5.0 L to a final volume of 20.0 L at a constant pressure of 350 kPa. How much work is done by the gas?

A)8.75 kJ
B)5.25 kJ
C)-5.25 kJ
D)-8.75 kJ

Question 16

In which one of these ways does the pressure in lungs at rest compare with atmospheric pressure?

A)always higher
B)always lower
C)always the same
D)varies during the breathing cycle

Question 17

A gas is heated at a constant pressure of 135 kPa, from an initial volume of 0.040 m³ and temperature of 20°C to a final volume of 0.06 m³ and a temperature of 25°C. How much heat flows into or out of the system?

A)1.3 kJ into system
B)2.6 kJ out of system
C)2.6 kJ into system
D)5.2 kJ out of system

Question 18

How does the molar heat capacity of an ideal gas relate to the composition of that gas?

A)It is constant for all gases.
B)It depends on the number of moles of gas.
C)It depends on the mass of gas.
D)It varies with temperature.

Question 19

Figure 9.2 T-V diagram with four processes for an ideal gas.
In Fig. 9.2, which process does path (B) represent?

A)isobaric expansion
B)isochoric compression
C)isobaric compression
D)isothermal compression

Question 20

In Joule's experiment, if a 10.0 kg mass falls a distance of 1.0 m, and the paddle is immersed in a 0.5 L beaker of mercury, what is the rise in temperature of the mercury, given that its mass density is 13.5 g/cm³ and its specific heat capacity is 138 J/(kg °C)?

A)1.0°C
B)0.1°C
C)0.01°C
D)0.001°C

Question 21

If the fluid in Joule's experiment were replaced by an equal mass of mercury, the measured rise in temperature would be greater than that for water.

Question 22

Under which of these conditions does an ideal gas experience the greatest gain in internal energy while undergoing reversible compression?

A)at constant pressure
B)at constant temperature
C)adiabatically
D)when pressure is proportional to volume

Question 23

In normal breathing, the majority of the work required comes from the inhaled air.

Question 24

Which of the following happens when a gas expands adiabatically?

A)The internal energy increases.
B)The internal energy decreases.
C)There is no work done by the gas.
D)There is work done on the gas.

Question 25

An ideal monatomic gas undergoes a reversible expansion to twice its original volume. Under which one of the following conditions does the gas perform the least amount of work?

A)at constant pressure
B)at constant temperature
C)adiabatically
D)as pressure increases in proportion to its volume

Question 26

For an ideal gas undergoing an isochoric process, the rise in temperature is proportional to the amount of heat absorbed.

Question 27

During inhalation, the pressure in the lungs is less than atmospheric pressure.

Question 28

Which of these statements does NOT describe a reversible process?

A)The system can be returned to its original state.
B)The system passes through a continuous sequence of equilibrium states.
C)Behaviour of the system is the same when going forward in time as when going backward.
D)The system and its environment can be returned to their original states.

Question 29

Entropy is a variable of state.

Question 30

A diesel engine uses adiabatic heating to ignite the fuel.

Question 31

Compressing gas in a closed system does negative work on the gas.

Question 32

In a reversible process, the temperature of an ideal gas is kept constant as the gas is compressed. The gas must absorb heat from its surroundings.

Question 33

When a gas undergoes an isothermal expansion, its entropy increases.

Question 34

Cyclic processes may be reversible or irreversible.

Question 35

An ideal monatomic gas undergoes a reversible expansion to twice its original volume. Under which of these conditions does the gas perform the most work?

A)at constant pressure
B)at constant temperature
C)adiabatically
D)pressure increases in proportion to its volume

Question 36

In the first law of thermodynamics, W is the work done on the system; that is, W is positive if work is done on the system.

Question 37

A certain ideal gas has an adiabatic coefficient of ê = 4/3. What is its molar specific heat at constant pressure?

A)4R
B)5R/3
C)3R/2
D)2R/3

Question 38

Which of these statements accurately describes how the efficiency of the Carnot cycle depends on the system?

A)It depends on the amount of heat absorbed or lost during each isothermal phase.
B)It is a function of the initial and final temperatures of the heat reservoirs.
C)It is different when the cycle is performed in reverse.
D)It is independent of any system parameters.

Question 39

At what lower temperature does a reversible engine operating from a high temperature of 600 K have the same efficiency as another reversible engine operating between 400 K and 750 K?

A)350 K
B)330 K
C)320 K
D)290 K

Question 40

The sum of all energy forms in a closed system is constant.

Question 41

For a polyatomic gas, some internal energy may be stored as vibrational and/or rotational energy within the molecules. Describe what effect this will have on the adiabatic coefficient ê, which has the value 5/3 when only translational motion of molecules is allowed.

Question 42

When a parcel of air is heated over a surface, it expands, thereby lowering its density relative to its surroundings, and experiences a buoyancy force, causing it to rise. Suppose that the ambient air is cold at the bottom and warmer at the top, giving rise to a "thermal inversion." What do you expect would happen to the heated parcel of air if this inversion were sufficiently strong, assuming the parcel expands adiabatically?

Question 43

Explain the difference between gauge pressure and absolute pressure.

Question 44

What characterizes the thermal energy of a system? Explain the difference between heat and thermal energy.

Question 45

Describe what distinguishes thermal energy from other forms of energy.

Question 46

Two identical samples of gas at the same pressure and volume are compressed to the same final volume. If the first sample undergoes isothermal compression and the second sample adiabatic compression, compare the outcomes of the two processes.

Question 47

Entropy of isolated systems undergoing irreversible processes increases and reaches a maximum when equilibrium is reached. What implications does this have for our universe?

Question 48

How did Joule's experiments lead to the formulation of the first law of thermodynamics?

Question 49

Describe how you might use a waterfall to measure the equivalence of thermal and mechanical heat. What complications might make this experiment difficult to perform?

Question 50

Describe how you would improve the efficiency of a real engine operating between two reservoirs at temperatures T_high and T_low.

Question 51

In the Carnot process, described in Section 9.6.2, heat is absorbed from a reservoir at a high temperature and heat is released to another reservoir at a lower temperature. Is it possible to run the cycle in reverse? If so, what effect would be achieved?

Question 52

Given some experimental data on pressure-versus-volume measurements, describe, in practical terms, how you would determine the work done by or on a system undergoing a cyclic process.