1. Harmonic Motion Not Linear Motion—been there, done that

2. Harmonic Motion - definition • Motion that repeats • Motion that has a cycle • Motion that swings back and forth

3. Harmonic Motion - examples • Person swinging on a swing Can you think of others? • Water cycle • Motion of a yoyo • Rotation of the earth on its axis

4. Harmonic motion definitions • Cycle– Building block of harmonic motion; unit of motion that repeats over and over • Period– Time needed to repeat one cycle • System – A group we choose that includes all the things we are interested in

5. More definitions • Oscillator – A system that shows harmonic motion (A pendulum is an oscillator.) • Examples of other oscillators: - Light and sound come from oscillations - Music and musical instruments are oscillators - Cell phones, radio broadcasts, clocks make use of oscillations

6. Characteristics of cycles • Period: Time for one cycle; how long a cycle lasts; period (of time) is usually measured in seconds. • Frequency: number of cycles per second Hertz--unit of frequency (one hertz is one cycle/second) Relationship between Period and Frequency: F = 1 / t t = 1 / F

7. Calculate the frequency of a pendulum that has a period of ¼ second. • Solution: • You are asked for frequency. • You are given period. • Relationship is F = 1 / t • Substitute numbers:F = 1 / 0.25 sec = 4 hz

8. Characteristics of cycles • Amplitude how big the cycle is; the maximum distance an object moves from its rest position (we can vary the amplitude of a pendulum) • If you know the period or frequency and the amplitude, then you have defined the motion of the oscillator. • Damping The slowing down of the motion; loss in amplitude over time FA

9. Harmonic or not? • A moving rocking chair • Bike ride to a friend’s house • Bike pedals during #2 • Your schedule at CJHS

10. Check Your Understanding • Obtain a colored card stack and be ready to hold up the correct card representing the correct answer for the following questions.

11. #1 The characteristics of a cycle are:A. Period, Cycle, OscillationB. Period, Cycle, FrequencyC. Period, Frequency, AmplitudeD. Period, Frequency, Oscillation

12. #1 The characteristics of a cycle are:A. Period, Cycle, OscillationB. Period, Cycle, FrequencyC. Period, Frequency, AmplitudeD. Period, Frequency, Oscillation

13. #2 If the frequency is 0.5 cycles/second, then the period is:A. 2 seconds B. 0.25 secondsC. 2 hertzD. 0.25 hertz

14. #2 If the frequency is 0.5 cycles/second, then the period is:A. 2 secondsB. 0.25 secondsC. 2 hertzD. 0.25 hertz

15. #3 If the period is 5 seconds, then the frequency is:A. 0.2 newtons B. 0.2 hertz C. 0.2 watts D. 0.2 seconds

16. #3 If the period is 5 seconds, then the frequency is:A. 0.2 newtons B. 0.2 hertzC. 0.2 watts D. 0.2 seconds