Physics

John D. Cutnell, Kenneth W. Johnson, David Young, Shane Stadler

ISBN #9781118486894

10th Edition

2,562 Questions

29,070 Students Helped

Homework Questions

Summary

Learning Objectives

Key Concepts

Example Problems

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Summary

This module on thermodynamics covers the fundamental laws that govern heat and work, the definitions of thermodynamic systems and processes, and the essential concepts of internal energy and entropy. It explains the mechanics behind various thermal processes, including isothermal, adiabatic, isobaric, and isochoric processes, and highlights the idealized Carnot engine which sets the maximum theoretical efficiency. Additionally, it introduces wave types in a brief section on sound and waves, providing a foundation for understanding how disturbances propagate. Key takeaways include the importance of sign conventions in energy calculations, the irreversibility of natural processes leading to entropy increase, and the practical limitations on device efficiency imposed by thermodynamic principles.

Learning Objectives

Key Concepts

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Example Problems

Example 1

I. In moving out of a dormitory at the end of the semester, a student does $1.6 \times 10^{4} \mathrm{J}$ of work. In the process, his internal energy decreases by 4.2 $\times 10^{4}$ J. Determine each of the following quantities (including the algebraic sign): (a) $W$ (b) $\Delta U$ (c) $Q$.

Example 2

The first law of thermodynamics states that the change $\Delta U$ in the inter- nal energy of a system is given by $\Delta U=Q-W$, where $Q$ is the heat and $W$ is the work. Both $Q$ and $W$ can be positive or negative numbers. $Q$ is a positive number if _________ , and $W$ is a positive number if _________. (a) the system loses heat; work is done by the system (b) the system loses heat; work is done on the system (c) the system gains heat; work is done by the system (d) the system gains heat; work is done on the system.

Example 3

The internal energy of a system changes because the system gains $165 \mathrm{J}$ of heat and performs $312 \mathrm{J}$ of work. In returning to its initial state, the system loses 114 J of heat. During this return process, (a) what work is involved, and (b) is the work done by the system or on the system?

Example 4

A system does 164 J of work on its environment and gains 77 J of heat in the process. Find the change in the internal energy of (a) the system and (b) the environment.

Example 5

A system does $4.8 \times 10^{4} \mathrm{J}$ of work, and $7.6 \times 10^{4} \mathrm{J}$ of heat flows into the system during the process. Find the change in the internal energy of the system.