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Ch.5 - Thermochemistry
All textbooksBrown 14th EditionCh.5 - ThermochemistryProblem 19
Chapter 5, Problem 19

Identify the force present and explain whether work is being performed in the following cases: (a) You lift a book off the top of a desk. (b) Air is compressed in a bicycle pump.

Verified step by step guidance
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Step 1: Identify the forces involved in each scenario. For (a), when you lift a book, the primary force is the gravitational force acting downward on the book, and the force you apply upward to lift it. For (b), when air is compressed in a bicycle pump, the force is applied by the piston compressing the air inside the pump.
Step 2: Define work in a physics context. Work is done when a force causes a displacement of an object in the direction of the force. Mathematically, work (W) is defined as W = F \cdot d \cdot \cos(\theta), where F is the force applied, d is the displacement, and \(\theta\) is the angle between the force and the displacement vector.
Step 3: Analyze scenario (a). When you lift a book, the force you apply is in the upward direction, and the displacement of the book is also upward. Since the force and displacement are in the same direction, work is being done on the book.
Step 4: Analyze scenario (b). In the case of compressing air in a bicycle pump, the force applied by the piston is in the direction of the displacement of the air being compressed. Therefore, work is being done on the air as it is compressed.
Step 5: Conclude whether work is performed. In both scenarios, work is performed because there is a force applied that causes a displacement in the direction of the force. In (a), work is done on the book, and in (b), work is done on the air inside the pump.

Key Concepts

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

Work in Physics

In physics, work is defined as the product of the force applied to an object and the distance over which that force is applied, in the direction of the force. Mathematically, it is expressed as W = F × d × cos(θ), where θ is the angle between the force and the direction of motion. Work is only done when a force causes displacement; if there is no movement, no work is performed.
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Forces in Lifting

When lifting an object, such as a book, the force exerted must overcome the gravitational force acting on the object. This upward force does work on the book as it moves against gravity, resulting in an increase in the book's gravitational potential energy. The work done is equal to the weight of the book multiplied by the height it is lifted.
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Compression of Gases

When air is compressed in a bicycle pump, work is done on the gas as the piston moves inward, increasing the pressure and decreasing the volume of the air. This process involves applying a force over a distance, resulting in work being performed on the gas. The work done is related to the change in volume and pressure of the gas, following the principles of thermodynamics.
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Related Practice
Textbook Question

A sodium ion, Na+, with a charge of 1.6⨉10-19 C and a chloride ion, Cl - , with charge of -1.6⨉10-19 C, are separated by a distance of 0.50 nm. How much work would be required to increase the separation of the two ions to an infinite distance?

Textbook Question

A magnesium ion, Mg2+, with a charge of 3.2⨉10-19 C and an oxide ion, O2-, with a charge of -3.2⨉10-19 C, are separated by a distance of 0.35 nm. How much work would be required to increase the separation of the two ions to an infinite distance?

Textbook Question

In a thermodynamic study, a scientist focuses on the properties of a solution in an apparatus as illustrated. A solution is continuously flowing into the apparatus at the top and out at the bottom, such that the amount of solution in the apparatus is constant with time. (a) Is the solution in the apparatus a closed system, open system, or isolated system?

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Textbook Question

In a thermodynamic study, a scientist focuses on the properties of a solution in an apparatus as illustrated. A solution is continuously flowing into the apparatus at the top and out at the bottom, such that the amount of solution in the apparatus is constant with time. (b) If the inlet and outlet were closed, what type of system would it be

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