/6thfm: Guitar string fundmtl. freq. = 256Hz, why does 384Hz tuning fork NOT vibrate?
A guitar string with a fundamental frequency of 256Hz is plucked. 2 tuning forks on a table have NATURAL frequencies of 512Hz and 384Hz respectively. Which fork(s) vibrate too?
I said the 512Hz fork will vibrate, perhaps at half the speed of the guitar string, because 512/256 = 2. For the 384Hz fork, I thought that would vibrate too, because two thirds of 384 = 512. I'm not sure why I thought this...but it makes sense..but not really because that fork apparently doesn't vibrate. So why DOES the 512Hz fork vibrate then?
Thank you
I said the 512Hz fork will vibrate, perhaps at half the speed of the guitar string, because 512/256 = 2. For the 384Hz fork, I thought that would vibrate too, because two thirds of 384 = 512. I'm not sure why I thought this...but it makes sense..but not really because that fork apparently doesn't vibrate. So why DOES the 512Hz fork vibrate then?
Thank you
Think about the wavelengths and what the length of the string must be.
Original post by teachercol
Think about the wavelengths and what the length of the string must be.
I think fund. freq is half a wavelength = length of string. So when wave vibrates at the 2nd harmonic (1st overtone) it represents 1 wavelength, so frequency is 512Hz. At the next, it is 1.5 wavelengths, and 768Hz..which is twice the natural frequ of the tuning fork. Still confused
Does the tuning fork not vibrate at any freq. except it's natural one then (as in it cant vibrate at 768Hz, or any freq. except 384Hz?)?
The question is not well thought out.
The guitar string's fundamental is 256 and it will have overtones at 512, 768 and further multiples of that fundamental.
I suspect you are meant to assume that the tuning forks will only be set in motion by a frequency equal to their fundamental. Tuning forks produce an almost perfect sinusoidal waveform and so vibrate almost exclusively in their fundamental mode with virtually no higher harmonics.
So the 1st overtone (2nd harmonic) of the guitar string will resonate with the fundamental of the 512 tuning fork.
It's unlikely that the question wanted you to consider the possibility of the 768 overtone of the string exciting the 2nd harmonic of the 384 fork.
Questions like these can actually succeed in confusing students more than helping. At least by looking at the physics here, you can hopefully see what the principle was that they were testing, and ponder whether the question was particularly good at extracting that understanding.
If it was single answer multiple choice then it was badly constructed. If it allowed you to state or explain what I have in my reply, and get credit for this, then maybe it was ok.
The guitar string's fundamental is 256 and it will have overtones at 512, 768 and further multiples of that fundamental.
I suspect you are meant to assume that the tuning forks will only be set in motion by a frequency equal to their fundamental. Tuning forks produce an almost perfect sinusoidal waveform and so vibrate almost exclusively in their fundamental mode with virtually no higher harmonics.
So the 1st overtone (2nd harmonic) of the guitar string will resonate with the fundamental of the 512 tuning fork.
It's unlikely that the question wanted you to consider the possibility of the 768 overtone of the string exciting the 2nd harmonic of the 384 fork.
Questions like these can actually succeed in confusing students more than helping. At least by looking at the physics here, you can hopefully see what the principle was that they were testing, and ponder whether the question was particularly good at extracting that understanding.
If it was single answer multiple choice then it was badly constructed. If it allowed you to state or explain what I have in my reply, and get credit for this, then maybe it was ok.
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