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Standing Waves on a String

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This is an experiment with standing waves on a string. Right now this string is vibrating in its fundamental mode. Let's see how we're doing it. I just turned off the oscillator; the oscillator is like a speaker where there's a diaphragm that moves like this and we set the frequency of vibration with this oscillator right here. The string it's a very light weight string and it goes over a pulley at this end. And then we have weight hanging off of this end a total of 350 grams on the end of the string.

I'm going to put this back into vibration at its fundamental frequency. And we'll give you a chance to record the frequency and then I will increase the frequency to higher harmonics, and then we'll record the frequencies for those. Ok, now let's get back to the fundamental. I'm going to adjust this just a little bit to see if I can fine tune it. We'll zoom in on the oscillator and get a reading on the frequency of it. Now we'll increase the frequency to get the second harmonic. Now you know from previous work this should be exactly twice the fundamental. I'm going to come around to the front and approximately double the reading of this on the oscillator so that's going to take it up to somewhere around thirty. And now I'm watching the string I'm going to fine tune it to see if I can get the maximum amplitude, that should do it. We'll zoom in for a reading on the meter. This should be three times the frequency of the fundamental. Alright this is pretty close to the third harmonic, so we'll zoom in for a frequency of the reading on that. Now I have a problem for you. I've made a change I've put additional mass on the end of the string so that there's more tension. I have the frequency adjusted for this particular case for four antinodes or an equal four. So let's zoom in and get the frequency And you should have enough information at this point in order to figure out how much mass is hanging on the end of the string, so that's the problem.

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