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Math Help - Simple Harmonic Motion

  1. #1
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    Simple Harmonic Motion

    Question:



    Answer:



    Problem:
    I don't understand why they have used -1 as x in part (b). Where did it come from? Thanks in advance.
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    Does the picture help?

    Bobak
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  3. #3
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    Quote Originally Posted by Air View Post
    ...
    I don't understand why they have used -1 as x in part (b). Where did it come from? Thanks in advance.
    I only can guess:

    11\ am = -1\ pm

    According to the given results the argument of the function is time.
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    Quote Originally Posted by Air View Post
    Question:



    Answer:



    Problem:
    I don't understand why they have used -1 as x in part (b). Where did it come from? Thanks in advance.
    Their model is incomplete.

    The correct model (taking t = 0 to correspond to 11:00 am) is x = 4 \cos \left( \frac{4 \pi}{25} t \right) {\color{red}+ 10}.

    Now substitute x = 9 ....
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  5. #5
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    Quote Originally Posted by earboth View Post
    I only can guess:

    11\ am = -1\ pm

    According to the given results the argument of the function is time.
    No x is displacement about the centre of oscillation.

    Bobak
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    Also, the depth of 9m is 11 \ \mathrm{am}+3.6277 \ \mathrm{Hours} = 2.6277 \ \mathrm{pm}. How did they convert that to 2.38 \ \mathrm{pm}?
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  7. #7
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    Quote Originally Posted by Air View Post
    Also, the depth of 9m is 11 \ \mathrm{am}+3.6277 \ \mathrm{Hours} = 2.6277 \ \mathrm{pm}. How did they convert that to 2.38 \ \mathrm{pm}?
    3.6277 hours is 3 hours 37 minutes and 39 seconds.

    look for a button like the one i circled on your calculator, that will do the conversion.

    Bobak
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    Quote Originally Posted by Air View Post
    Also, the depth of 9m is 11 \ \mathrm{am}+3.6277 \ \mathrm{Hours} = 2.6277 \ \mathrm{pm}. How did they convert that to 2.38 \ \mathrm{pm}?
    Think of 2.6277 as degrees .... The 0.6277 then converts to 37 minutes and 39.72 seconds ...... (Remember that 1 hour = 60 minutes and 1 minute = 60 seconds which is why the angle analogy works).
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