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Review the units of work, energy, force, and distance. Use the equations for mechanical energy and work to show what is work and what is not. Make it clear why holding something off the ground or carrying something over a level surface is not work in the scientific sense.
- 15.1 The Electromagnetic Spectrum
Teacher Support [BL] Explain that the term spectrum refers...
- 22.4 Nuclear Fission and Fusion
As shown in Figure 22.26, a neutron strike can cause the...
- 23.1 The Four Fundamental Forces
Understanding the Four Forces. The gravitational force is...
- 11.1 Temperature and Thermal Energy
The Kelvin scale is the temperature scale that is commonly...
- 22.1 The Structure of The Atom
9 Work, Energy, and Simple Machines. Introduction; 9.1 Work,...
- 23.3 The Unification of Forces
As discussed earlier, the short ranges and large masses of...
- 21.3 The Dual Nature of Light
Figure 21.10 shows a comet with two prominent tails. Comet...
- 7.3 Work-Energy Theorem
Work-Energy Theorem. Draw a free-body diagram for each force...
- 15.1 The Electromagnetic Spectrum
Online Textbook. These notes were updated in 2022 to reflect corrections that readers have noticed. Chapter 1: Introduction to Classical Mechanics (PDF) Chapter 2: Units, Dimensional Analysis, Problem Solving, and Estimation (PDF - 4.5 MB) Chapter 3: Vectors (PDF - 4.4 MB)
Energy resources are key limiting factors to economic growth. The world use of energy resources, especially oil, continues to grow, with ominous consequences economically, socially, politically, and environmentally. We will briefly examine the world’s energy use patterns at the end of this chapter.
To understand energy and conservation of energy, we must first define some terms: work, kinetic energy (KE), and potential energy (PE). We’ll get to PE in the next Chapter. Let’s look at work and KE. Definition of work done by a force: consider an object moving while a constant force F is applied to the object.
Evaluate the work done for various forces. In physics, work is done on an object when energy is transferred to the object. In other words, work is done when a force acts on something that undergoes a displacement from one position to another.
Work-Energy Theorem. Draw a free-body diagram for each force on the object. Determine whether or not each force does work over the displacement in the diagram. Be sure to keep any positive or negative signs in the work done. Add up the total amount of work done by each force.
The concept of power originated from the studies of James Watt (1736-1819) as a way to compare the work done between steam engines and horses. This comparison was done in the absence of modern SI units, and with no energy concept (James Joule was 8 months old when Watt passed away).
