Chapter 4: Thermodynamics
EXERCISES [PAGES 107 - 108]
Exercises | Q 1.1 | Page 107
Choose the correct option.
A gas in a closed container is heated with 10 J of energy, causing the lid of the
container to rise 2m with 3N of force. What is the total change in energy of the system?
1. 10 J
2. 4 J
3. - 10 J
4. - 4 J
SOLUTION
4J
Explanation:
For this problem, use the first law of thermodynamics. The change in energy equals the
increase in heat energy minus the work done.
ΔU=Q-W
We are not given a value for work, but we can solve for it using the force and distance.
Work is the product of force and displacement.
W =F Δx
W = 3N × 2m
W =6 J
Now that we have the value of work done and the value for heat added, we can solve
for the total change in energy.
ΔU=Q-W
Δ U = 10 J - 6 J
ΔU=4J
, Exercises | Q 1.2 | Page 107
Choose the correct option.
Which of the following is an example of the first law of thermodynamics?
1. The specific heat of an object explains how easily it changes temperatures.
2. While melting, an ice cube remains at the same temperature.
3. When a refrigerator is unplugged, everything inside of it returns to room
temperature after some time.
4. After falling down the hill, a ball's kinetic energy plus heat energy equals th e
initial potential energy.
SOLUTION
While melting, an ice cube remains at the same temperature.
Exercises | Q 1.3 | Page 107
Choose the correct option.
Efficiency of a Carnot engine is large when
(A) TH is large
(B) Tc is low
(C) TH - Tc is large
(D) TH - Tc is small
SOLUTION
Exercises | Q 1.4 | Page 107
Choose the correct option.
The second law of thermodynamics deals with transfer of:
(A) work done
(B) energy
(C) momentum
(D) heat
EXERCISES [PAGES 107 - 108]
Exercises | Q 1.1 | Page 107
Choose the correct option.
A gas in a closed container is heated with 10 J of energy, causing the lid of the
container to rise 2m with 3N of force. What is the total change in energy of the system?
1. 10 J
2. 4 J
3. - 10 J
4. - 4 J
SOLUTION
4J
Explanation:
For this problem, use the first law of thermodynamics. The change in energy equals the
increase in heat energy minus the work done.
ΔU=Q-W
We are not given a value for work, but we can solve for it using the force and distance.
Work is the product of force and displacement.
W =F Δx
W = 3N × 2m
W =6 J
Now that we have the value of work done and the value for heat added, we can solve
for the total change in energy.
ΔU=Q-W
Δ U = 10 J - 6 J
ΔU=4J
, Exercises | Q 1.2 | Page 107
Choose the correct option.
Which of the following is an example of the first law of thermodynamics?
1. The specific heat of an object explains how easily it changes temperatures.
2. While melting, an ice cube remains at the same temperature.
3. When a refrigerator is unplugged, everything inside of it returns to room
temperature after some time.
4. After falling down the hill, a ball's kinetic energy plus heat energy equals th e
initial potential energy.
SOLUTION
While melting, an ice cube remains at the same temperature.
Exercises | Q 1.3 | Page 107
Choose the correct option.
Efficiency of a Carnot engine is large when
(A) TH is large
(B) Tc is low
(C) TH - Tc is large
(D) TH - Tc is small
SOLUTION
Exercises | Q 1.4 | Page 107
Choose the correct option.
The second law of thermodynamics deals with transfer of:
(A) work done
(B) energy
(C) momentum
(D) heat
