19.3 Resonance pp Mr. Richter
Agenda Warm-Up Questions about Percent Change? Notes: Natural Frequency Resonance Work on Pendulum Lab Analysis
Objectives: We Will Be Able To… Understand that all oscillators have a natural frequency of vibration. Describe a system in resonance.
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?
Natural Frequency
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.
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!
Resonance
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.
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.
Resonance Resonance is not always a good thing. Just ask the Tacoma Narrows Bridge.Tacoma Narrows Bridge
Wrap-Up: Did we meet our objectives? Understand that all oscillators have a natural frequency of vibration. Describe a system in resonance.
Homework p. 431 #14 p. 432 #10, 11