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Ch 10: Interactions and Potential Energy
Knight Calc - Physics for Scientists and Engineers 5th Edition
Knight Calc5th EditionPhysics for Scientists and EngineersISBN: 9780137344796Not the one you use?Change textbook
Chapter 10, Problem 39

How much work is done by the environment in the process shown in FIGURE EX10.39? Is energy transferred from the environment to the system or from the system to the environment?

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Step 1: Understand the concept of work in thermodynamics. Work is the energy transferred when a force is applied over a distance or when a system undergoes a volume change under pressure. In thermodynamics, work done by the environment on the system or vice versa is often calculated using the formula: W = PextdV, where Pext is the external pressure and dV is the change in volume.
Step 2: Analyze the figure (FIGURE EX10.39) to determine the type of process involved. For example, if the process is an isobaric (constant pressure) process, the work can be simplified to W = Pext×∆V, where ∆V is the change in volume. If the process is more complex, such as a curve on a pressure-volume graph, the work is calculated by finding the area under the curve.
Step 3: Determine the direction of energy transfer. If the volume of the system increases (∆V > 0), the system does work on the environment, and energy is transferred from the system to the environment. Conversely, if the volume decreases (∆V < 0), the environment does work on the system, and energy is transferred from the environment to the system.
Step 4: Use the given data from the figure to calculate the work. Identify the initial and final volumes (Vi and Vf) and the external pressure (Pext). Substitute these values into the formula for work.
Step 5: Interpret the result. Based on the sign of the calculated work, determine whether energy is transferred from the environment to the system (positive work) or from the system to the environment (negative work). This interpretation helps understand the thermodynamic interaction between the system and its surroundings.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Work

In physics, work is defined as the transfer of energy that occurs when a force is applied over a distance. It is calculated using the formula W = F × d × cos(θ), where W is work, F is the force applied, d is the distance moved in the direction of the force, and θ is the angle between the force and the direction of motion. Understanding work is crucial for analyzing energy transfers in a system.
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Energy Transfer

Energy transfer refers to the movement of energy from one system to another, which can occur in various forms such as heat, work, or mass transfer. In the context of thermodynamics, energy can be transferred from the environment to a system (gaining energy) or from a system to the environment (losing energy). Identifying the direction of energy transfer is essential for understanding the overall energy balance in a process.
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System and Environment

In thermodynamics, a system is defined as the part of the universe being studied, while the environment encompasses everything outside the system. The interaction between the system and its environment is critical for analyzing processes such as heat exchange and work done. Understanding the relationship between the system and the environment helps clarify whether energy is being absorbed or released during a process.
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