Vibrations

In previous lessons we’ve learned that energy is the ability to do work, and that work is moving something a distance against a force. The concept of energy is fairly easy to see as far as lifting things or pushing things go. We are exerting energy to lift a box against the force of gravity. We are exerting energy to pedal our bike up a hill. But how does this energy stuff relate to light, electricity, or sound? What’s moving against a force there?

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Damping is when a spring, swing, or other vibrating object loses its energy over time. It means that without adding energy into the system, like pumping on a swing or hitting a drum head, the object will eventually come to its non-vibrating (equilibrium) position.

Imagine the kid on the swing again. Why does the kid move past the equilibrium point without stopping?
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The concept of frequency is very important to understanding energy. When it comes to electromagnetic waves it is frequency that determines whether the wave is radio, light, heat, microwave or more. It’s all the same type of energy, it’s the frequency that determines what that energy actually does. With sound energy the frequency determines the pitch of the sound.

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The period is the time it takes for one full cycle to complete itself and is measured in seconds per cycle. The frequency is the number of cycles that are make in a period of time, and is measured in cycles per second.

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The frequency is the number of cycles that are made in a given period of time, like 10 swings in 5 seconds, and is measured in cycles per second. The period is the inverse of the frequency, given by this equation: T = 1/ν.

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Amplitude is how high or low the wave is from its original equilibrium position. (not vibrating). How high can you get the swing to go? How far does the car system spring travel over that bump? All these are the amplitude of the vibration.

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The restoring force slows down the object as it moves from its resting but speeds it up when it heads back to the resting position, and that’s what creates the vibration. We’re going to take a look at the forces in a pendulum from the point of view of Newton’s Laws.
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There’s more than one way to solve physics problems… and by looking at the total mechanical energy of the system, you’ll be able to solve much more complicated pendulum problems with ease.

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You’ll need a pendulum for this experiment. A pendulum is really nothing more than a weight at the end of something that can swing back and forth. The easiest way to make one is to get a string and tape it to the edge of a table. (The string should be long enough so that it swings fairly close to the ground.) Tie a weight to the bottom of your string and you’ve got a pendulum.
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How are pendulums like springs? They both vibrate, but how you model them on paper is a little different. Let’s take a look at how you handle springs and what their periodic nature looks like:
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