The back-and-forth vibratory motion (often called oscillatory motion) of a swinging pendulum is called simple harmonic motion. The pendulum bob filled with sand in Figure 25.2 25.2 exhibits simple harmonic motion above a conveyor belt. When the conveyor belt is stationary, the sand traces out a straight line. More interestingly, when the conveyor belt is moving at constant speed, the sand traces out a special curve known as a sine curve. A sine curve is a pictorial representation of a wave. The source of all is something that vibrates. think! What is the frequency in vibrations per second of a 100-Hz wave? Answer: 25.2.1 FIGURE 25.2 Frank Oppenheimer, founder of the Exploratorium® science museum in San Francisco, demon- strates that a pendulum swinging back and forth traces out a straight line over a stationary surface and a sine when the surface moves at constant speed. The period of the CHECK pendulum depends only on the length of a pendulum and the acceleration of gravity. CONCEPT Teaching Resources Problem-Solving Exercises in • Physics 12-1, 12-2 Laboratory Manual 68, 69 • Probeware Lab Manual 13 • ...... CHAPTER 25 VIBRATIONS AND WAVES 491 491
The back-and-forth vibratory motion (often called oscillatory motion) of a swinging pendulum is called simple harmonic motion. 25.2 The pendulum bob filled with sand in Figure 25.2 exhibits simple harmonic motion above a conveyor belt. When the conveyor belt is stationary, the sand traces out a straight line. More interestingly, when the conveyor belt is moving at constant speed, the sand traces out a special curve known as a sine curve. A sine curve is a pictorial representation of a wave. The source of all is something that vibrates. think! What is the frequency in vibrations per second of a 100-Hz wave? Answer: 25.2.1 FIGURE 25.2 Frank Oppenheimer, founder of the Exploratorium® science museum in San Francisco, demon- strates that a pendulum swinging back and forth traces out a straight line over a stationary surface and a sine when the surface moves at constant speed. The period of the CHECK pendulum depends only on the length of a pendulum and the acceleration of gravity. CONCEPT Teaching Resources • Problem-Solving Exercises in Physics 12-1, 12-2 • Laboratory Manual 68, 69 • Probeware Lab Manual 13 ...... CHAPTER 25 VIBRATIONS AND WAVES 491 491