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16 .42.
00:02
So we have a string under some initial tension oscillating in its third harmonic, which has a frequency of f3 and a wavelength of lambda 3.
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And then we increase its tension to four times its initial value, and it's again oscillating in its third harmonic.
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And so we want to find what that frequency is in terms of the original one and what the wavelength is in terms of the original one.
00:26
And i've gone ahead and called the new ones primes, just to differentiate them between from the other ones.
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So starting off with, before we embark on part a, we start off with just writing down what this frequency looks like from the initial case.
00:49
We know that the nth harmonic looks like nv over 2l.
00:56
Now we know that v is the square root of the tension divided by the density.
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And so our initial f3 is 3 over 2l times the square root of the initial tension divided by the density.
01:36
And so now we can go right ahead and look at this and we see that f3 prime is going to be 3 over 2l times the square root of 4 times the initial tension, because that's what our tension in the new case is, divided by new, so then if we take 4 out of the square root, it becomes 2.
02:20
We can see here that this is just f3 again...