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    Please can you help me on Question 3 on this jan 2009 paper.... i cant seem to get the right frequency! Jan 09 PA.pdf


    THANKS!
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    Okay so on the trace in the paper you can see that there are 3 peaks telling you that in 10ms (that is 1x10^-2 s) there are 3 wavelengths past a set point.

    Frequency is wavelengths past a set point per second, and you know that 10ms goes into 1s 100 times. Therefore you know the approx frequency to be 3 (in 0.01s) x 100 (to get to 1s) giving you a frequency of 300Hz.

    Hope that helps.
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    Oh unless it means all the tiny wavelengths in which case it would be more like 1000Hz which seems more plausible


    EDIT: ok just seen the mark scheme and seems I was way off, sorry I couldn't be helpful!
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    (Original post by Salmonidae)
    Oh unless it means all the tiny wavelengths in which case it would be more like 10000Hz which seems more plausible


    EDIT: ok just seen the mark scheme and seems I was way off, sorry I couldn't be helpful!
    hmmm yes i did what you did at first, and now looking at the mark scheme, i think you have to count the tiny peaks... but still... i would not have worked that out in the exam!!
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    Yeah tough question. Is a legacy paper though!!
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    There are 5 small waves for every large one so the frequency of the small waves is 5 times that of the large.
    The large wave is 300Hz meaning the smaller is about 1500Hz
    You can also count 15 small waves to 3 large ones to get the same answer.
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    (Original post by Stonebridge)
    There are 5 small waves for every large one so the frequency of the small waves is 5 times that of the large.
    The large wave is 300Hz meaning the smaller is about 1500Hz
    You can also count 15 small waves to 3 large ones to get the same answer.
    Thanks! makes sense...
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    what people will do for pos reps.,:rolleyes:
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    (Original post by Maphs)
    what people will do for pos reps.,:rolleyes:
    well, i have to create interest.. or no-one will help me! Its a tough world... give some to get some. :cool:
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    really funny, i should use that technique some time, but what does that actually do to them if we give them a pos rating i dont see how that is beneficial to them??:confused:

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