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Thank you here's your shmoop du jour brought to you

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by standing waves Although we've been working on a lot

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of this physics stuff we'd prefer sitting wave Just get

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some rest all right A string is held taut and

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its tension results in a fourth harmonic standing wave With

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a wave velocity of ten meters per second Hugh walks

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over and grabs it fifteen centimeters from one end in

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an attempt to interfere with the wave If this action

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doesn't affect the way of what is a possible length

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for the string and hear the potential answers and be

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sure you really kind of figure out what's going on

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here right so hugh here just has to mess with

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the string Some people take hands on physics a little

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too literally but if he grabs the string at a

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certain point and it doesn't affect the wave that means

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he's grabbed it at one of the waves Notes Well

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that's a good piece of info to know we'll let

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you off easy this time but next time he's exiled

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from the study A fourth harmonic standing wave means there

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are four anti notes and five notes counting the nodes

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at each end of the string and that means that

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there are three other notes One has to be in

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the middle and the other two are at one quarter

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and three quarter points along the string so fifteen centimeters

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has to equal one quarter of the strings length one

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half of the strings length or three quarters of the

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strings length Doing the math shows is that a fifteen

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centimeters is a quarter of the strings Length in the

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string would be sixty centimetres long If fifteen centimeters is

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the halfway point then the string has to be thirty

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centimeters long which is great But neither of those are

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included in our possible choices But a fifteen centimeters is

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three quarters of the strings length than the whole string

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is twenty centimetres long Got it and that's one of

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our choices So the correct answer is d okay now

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we're really beat it's bedtime for us but have no 00:01:57.511 --> [endTime] fear Physics never sleep

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