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Chapter 28 | Special Relativity 1251
28 SPECIAL RELATIVITY
Figure 28.1 Special relativity explains why traveling to other star systems, such as these in the Orion Nebula, is unreasonable using our current level of technology. (credit: s58y, Flickr)
Chapter Outline
28.1. Einstein’s Postulates
28.2. Simultaneity And Time Dilation 28.3. Length Contraction
28.4. Relativistic Addition of Velocities 28.5. Relativistic Momentum
28.6. Relativistic Energy
Connection for AP® Courses
In this chapter you will be introduced to the theory of special relativity, which was first described by Albert Einstein in the year 1905. The chapter opens with a discussion of Einstein’s postulates that form the basis of special relativity. You will learn about an essential physics framework that is used to describe the observations and measurements made by an observer in what is called the “inertial frame of reference” (Enduring Understanding 3.A). Special relativity is a universally accepted theory that defines a relationship between space and time (Essential Knowledge 1.D.3). When the speed of an object approaches the speed of light, Newton’s laws no longer hold, which means that classical (Newtonian) mechanics (Enduring Understanding 1.D) is not sufficient to define the physical properties of such a system. This is where special relativity comes into play. Many interesting and counterintuitive physical results follow from the theory of special relativity. In this chapter we will explore the concepts of simultaneity, time dilation, and length contraction.
Further into the chapter you will find information that supports the concepts of relativistic velocity addition, relativistic momentum, and energy (Enduring Understanding 4.C). Learning these concepts will help you understand how the mass (Enduring Understanding 1.C and Essential Knowledge 4.C.4) of an object can appear to be different for different observers and how matter can be converted into energy and then back to matter so that the energy of the system remains conserved. (Essential Knowledge 1.C.4 and Enduring Understanding 5.B). The information and examples presented in the chapter support Big Ideas 1, 3, 4, and 5 of the AP® Physics Curriculum Framework.
The content of this chapter supports:
Big Idea 1 Objects and systems have properties such as mass and charge. Systems may have internal structure.
Enduring Understanding 1.C Objects and systems have properties of inertial mass and gravitational mass that are experimentally verified to be the same and that satisfy conservation principles.
Essential Knowledge 1.C.4 In certain processes, mass can be converted to energy and energy can be converted to mass according to , the equation derived from the theory of special relativity.
Enduring Understanding 1.D Classical mechanics cannot describe all properties of objects. Essential Knowledge 1.D.3 Properties of space and time cannot always be treated as absolute.