Chapter 15 of cutnell and johnson"s "physics" textbook, 11th edition, focuses on simple harmonic motion. Simple harmonic motion is a type of motion that repeats itself over and over again in a regular pattern, and it is characterized by a restoring force that is proportional to the displacement from equilibrium. The chapter begins by introducing the concept of an oscillation, which is a back-and-forth motion around an equilibrium position. The period of an oscillation is the time it takes to complete one full cycle of motion, while the frequency is the number of cycles completed in one second. The amplitude is the maximum displacement from equilibrium. Next, the chapter discusses the different types of oscillations, including those that are damped and those that are driven. Damped oscillations decrease in amplitude over time due to the presence of friction or other forms of resistance, while driven oscillations are those that are periodically forced to oscillate.