Podcast
Questions and Answers
An office worker claims their cold coffee warmed to 80°C by absorbing energy from the 25°C air. Is this plausible? Does it violate thermodynamic laws?
An office worker claims their cold coffee warmed to 80°C by absorbing energy from the 25°C air. Is this plausible? Does it violate thermodynamic laws?
This is not plausible and violates the second law of thermodynamics, which states that heat cannot spontaneously flow from a colder body to a warmer body without external work being done.
What is the net force acting on a car moving at a constant velocity on a level road and on an uphill road?
What is the net force acting on a car moving at a constant velocity on a level road and on an uphill road?
On a level road, the net force is zero. On an uphill road, assuming constant velocity, the net force is also zero. This implies the driving force equals the gravitational force component acting downhill.
A car engine's radiator rejects heat to the air via circulating water. Should the radiator be modeled as a closed or open system? Explain.
A car engine's radiator rejects heat to the air via circulating water. Should the radiator be modeled as a closed or open system? Explain.
The radiator should be analyzed as an open system because mass (water) crosses the system boundary as it circulates to remove heat.
To understand a reciprocating air compressor, what type of thermodynamic system is most appropriate? Why?
To understand a reciprocating air compressor, what type of thermodynamic system is most appropriate? Why?
A room-temperature soft drink can is placed in a refrigerator. Should it be modeled as a closed or open system to analyze its cooling process? Explain.
A room-temperature soft drink can is placed in a refrigerator. Should it be modeled as a closed or open system to analyze its cooling process? Explain.
What are intensive and extensive properties? Give an example of each.
What are intensive and extensive properties? Give an example of each.
Is the weight of a system an intensive or extensive property? Explain why.
Is the weight of a system an intensive or extensive property? Explain why.
A rigid container is filled with a mixture of air and fuel. Is the density of the mixture an intensive or extensive property? Explain.
A rigid container is filled with a mixture of air and fuel. Is the density of the mixture an intensive or extensive property? Explain.
Describe the difference between a steady-flow process and a transient process. Give an example of each.
Describe the difference between a steady-flow process and a transient process. Give an example of each.
A pressure cooker is sealed and heated on a stove. Is this best modeled as a closed system or an open system? Explain.
A pressure cooker is sealed and heated on a stove. Is this best modeled as a closed system or an open system? Explain.
Define thermodynamic equilibrium. What conditions must be met for a system to be in thermodynamic equilibrium?
Define thermodynamic equilibrium. What conditions must be met for a system to be in thermodynamic equilibrium?
During a hot summer day, you notice water droplets forming on the outside of a cold beverage can. Is this an example of a closed or open system interaction? Explain.
During a hot summer day, you notice water droplets forming on the outside of a cold beverage can. Is this an example of a closed or open system interaction? Explain.
Explain the zeroth law of thermodynamics and its significance.
Explain the zeroth law of thermodynamics and its significance.
Describe how a thermometer works in terms of achieving thermal equilibrium.
Describe how a thermometer works in terms of achieving thermal equilibrium.
Why is it important to define a system boundary when analyzing a thermodynamic problem?
Why is it important to define a system boundary when analyzing a thermodynamic problem?
What is the difference between gauge pressure and absolute pressure? How are they related?
What is the difference between gauge pressure and absolute pressure? How are they related?
Describe the concept of specific volume. How is it related to density?
Describe the concept of specific volume. How is it related to density?
Explain what is meant by the term 'state postulate'.
Explain what is meant by the term 'state postulate'.
What is the difference between energy transfer by heat and energy transfer by work? Give an example of each.
What is the difference between energy transfer by heat and energy transfer by work? Give an example of each.
Explain the concept of quasi-equilibrium process. Why is it important in thermodynamics?
Explain the concept of quasi-equilibrium process. Why is it important in thermodynamics?
Flashcards
Cold coffee warming up claim
Cold coffee warming up claim
No, this claim is not true, as it violates the second law of thermodynamics, which states that heat cannot spontaneously flow from a colder to a hotter body.
Net force on a car at constant velocity
Net force on a car at constant velocity
The net force is zero when cruising at a constant velocity, as there is no acceleration in either scenario.
Radiator as a thermodynamic system
Radiator as a thermodynamic system
The radiator should be analysed as an open system, as mass (air) crosses the boundary.
Reciprocating air compressor (piston-cylinder)
Reciprocating air compressor (piston-cylinder)
Signup and view all the flashcards
Cooling a soft drink can
Cooling a soft drink can
Signup and view all the flashcards
Intensive vs. Extensive Properties
Intensive vs. Extensive Properties
Signup and view all the flashcards
Weight: Intensive or Extensive?
Weight: Intensive or Extensive?
Signup and view all the flashcards
Study Notes
- A1 - Introduction to Thermodynamics
Question 1
- An office worker claims their cold coffee warmed up to 80°C by absorbing energy from the 25°C surrounding air.
- There is no truth to this claim.
- This process violates the second law of thermodynamics.
- Heat transfer occurs from a higher temperature to a lower temperature.
- The surrounding air at 25°C cannot spontaneously heat the coffee to 80°C.
Question 2
- Net force on a car cruising at a constant velocity on a level road: zero.
- Net force on a car cruising at a constant velocity on an uphill road: zero.
- Constant velocity implies no acceleration according to Newton's First Law.
- If there is no acceleration, the net force acting on the car is zero.
Question 3
- A car radiator should be analyzed as an open system.
- A large fraction of thermal energy is rejected to the air by the radiator using circulating water.
- The radiator exchanges both energy (heat) and mass (circulating water) with its surroundings.
- An open system allows both mass and energy transfer across its boundaries.
Question 4
- A reciprocating air compressor (piston-cylinder device) should be analyzed as a closed system.
- The air inside the cylinder is compressed, but no mass crosses the system boundary (the cylinder walls).
- A closed system allows energy transfer (work, heat), but no mass transfer across its boundaries.
Question 5
- A can of soft drink being cooled in a refrigerator can be modeled as a closed system.
- The mass of the soft drink remains constant.
- Only energy (heat) is transferred from the can to the refrigerator compartment.
- A closed system involves energy transfer, but not mass transfer.
Question 6
- Intensive properties: do not depend on the size or extent of the system (e.g., temperature, pressure, density).
- Extensive properties: depend on the size or extent of the system (e.g., mass, volume, total energy).
Question 7
- The weight of a system is an extensive property.
- Weight depends on the mass of the system.
- The greater the mass of the system, the higher the weight.
- Extensive properties are additive; weight increases with system size.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
