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    I'm struggling with an mcq question here. Could anyone tell me why the maximum velocity is pi m/s? Urgent please. Thanks
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    (Original post by Ridah)
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    I'm struggling with an mcq question here. Could anyone tell me why the maximum velocity is pi m/s? Urgent please. Thanks
    They've swapped the labelling for the axes, BTW, but ... the magnitude of the max velocity for SHM is:

    v_{\text{max}} = \omega A = 2\pi f A = \frac{2 \pi A}{T}

    so just read the appropriate numbers off the graph, and plug them in.
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    (Original post by Ridah)

    I'm struggling with an mcq question here. Could anyone tell me why the maximum velocity is pi m/s? Urgent please. Thanks
    From the graph x = \frac{\pi}{2}\cos 2t \Rightarrow x' = v = -\pi \sin 2t which is maximum precisely when \sin 2t = -1 and v = \pi \, \mathrm{ms}^{-1}.
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    (Original post by Zacken)
    From the graph x = \frac{\pi}{2}\cos 2t \Rightarrow x' = v = -\pi \sin 2t which is maximum precisely when \sin 2t = -1 and v = \pi \, \mathrm{ms}^{-1}.
    Where are you getting these numbers from? They don't look right to me.
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    (Original post by atsruser)
    Where are you getting these numbers from? They don't look right to me.
    What's your A and T? I mostly hazarded a guess from the axes, the amplitude looked like \frac{\pi}{2} and the period like \pi - I didn't see your answer before posting mine, whoops.
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    (Original post by Zacken)
    What's your A and T? I mostly hazarded a guess from the axes, the amplitude looked like \frac{\pi}{2} and the period like \pi - I didn't see your answer before posting mine, whoops.
    The 'period''s definitely 3m. I'd guess the 'amplitude' is 1.5s
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    (Original post by Alexion)
    The 'period''s definitely 3m. I'd guess the 'amplitude' is 1.5s
    Huh? The axes should be swapped, no?
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    (Original post by Zacken)
    Huh? The axes should be swapped, no?
    Yeah it's real confusing without the rest of the question to make it clearer :/
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    (Original post by Alexion)
    Yeah it's real confusing without the rest of the question to make it clearer :/
    Here is the question paper from what i can see:
    Question 1:
    Both of the responses here are correct, although i prefer the 2\pi fA method (because it works all the time every time)
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  1. File Type: pdf unit 5 physics oscillations questions.pdf (407.0 KB, 262 views)
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    (Original post by Zacken)
    Huh? The axes should be swapped, no?
    You don't seem to have done that, as far as I can tell from your numbers. It seems to work out fine if you swap the axes then read off the values. As it stands, the graph doesn't make much sense - time only seems to exist between -2 and +2.
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    (Original post by atsruser)
    You don't seem to have done that, as far as I can tell from your numbers. It seems to work out fine if you swap the axes then read off the values. As it stands, the graph doesn't make much sense - time only seems to exist between -2 and +2.
    I assumed it was a typo on the question setters part and mentally swapped the labels on the axes.
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    (Original post by Zacken)
    I assumed it was a typo on the question setters part and mentally swapped the labels on the axes.
    Err, yeah, but your numbers don't seem right though. T= 3 s, and A= 1.5 m, no?
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    (Original post by atsruser)
    Err, yeah, but your numbers don't seem right though. T= 3 s, and A= 1.5 m, no?
    Right... I'll need to get myself declared legally blind.
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    Thank you so much.
 
 
 
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