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Simple Harmonic Motion - Need some quick help! watch

    • Thread Starter

    Here is a screenshot of the question: http://prntscr.com/ao79xi
    The first part is fairly straight forward, I worked out the time period by doing the following calculation.
    T = no. of oscillations/time taken, 42/15= 2.8 Seconds

    However in the second part of the question I am incorrect, I did the following:
    Since it is asking us for her kinetic energy as she passed through the lowest point I was assuming that velocity is max, so I did this:
    Vmax = 2*Pi*f*A
    We are provided with the amplitude so with the given information I calculated Vmax to be 0.56m/s, then inputted these values in the kinetic energy formula, 1/2*m*v^2, which gave me a value of 2.82 J, I do not understand why this is incorrect? In the mark scheme they said that Ek = mgh, which gives the kinetic energy of the girl at the lowest point. (44 J). Thanks in advance!
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Updated: April 5, 2016

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