1. 19.3 Resonance pp. 425 -426 Mr. Richter

2. Agenda  Warm-Up  Questions about Percent Change?  Notes:  Natural Frequency  Resonance  Work on Pendulum Lab Analysis

3. Objectives: We Will Be Able To…  Understand that all oscillators have a natural frequency of vibration.  Describe a system in resonance.

4. Warm-Up:  A boy is measured to be 1.22 m tall. One year later, he is measured to be 1.37 m tall. According to our rule of thumb, is this a significant change in height?

5. Natural Frequency

6.  Every object that oscillates has at least one natural frequency of vibration, the frequency at which a system naturally oscillates.  This means that the object wants to vibrate at a certain frequency more than others.

7. Natural Frequency  If you change the object in some way(s) you can change the natural frequency.  In your lab, you changed the length of the pendulum, which changed the frequency.  Just like changing the length of a guitar string!

8. Resonance

9. Forced Vibrations  If a vibrating object is attached to another object, the other object will begin to vibrate as well.  Think of you kicking your legs sitting on a swing.  You vibrate, and the swing will vibrate as well.  This is called forced vibration. The vibrating object transfers energy to the other objects, increasing their amplitudes.vibrating object  If the force the vibrating object applies is at regular intervals, it is called a periodic force.

10. Resonance  When the forced vibration (input) is equal to the natural frequency of vibration of the object, the system is said to be in resonance.  Systems in resonance will transfer energy much more quickly from one object to another.resonance  To swing on the swings, you have to kick your feet at the correct intervals. Otherwise, chaos.

11. Resonance  Resonance is not always a good thing.  Just ask the Tacoma Narrows Bridge.Tacoma Narrows Bridge

12. Wrap-Up: Did we meet our objectives?  Understand that all oscillators have a natural frequency of vibration.  Describe a system in resonance.

13. Homework  p. 431 #14  p. 432 #10, 11