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SHM question

  1. Feb 4, 2014 #1
    I found this example in my physics textbook but it seems that the answers I get when I plug in the numbers are different to what the example says and I'm not so sure why?


    Image attached of course! ImageUploadedByPhysics Forums1391560973.780261.jpg


    It gives the phase as 7.5 which I got but when I used it in the equations I didn't get the correct answer, mine where


    x= 0.01m

    v= 0.952 m/s

    a= -1.5 m/s^2


    My working was trivial as well, I just plugged in the numbers and I have checked multiple times for an arithmetic error:)


    Thanks in advanced
     
  2. jcsd
  3. Feb 4, 2014 #2

    BvU

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    You've posted a number of times and don't make use of the template ? You should know by now we can't help you if you don't show the details of how you got x, v and a.
    In this case it isn't even the eagerness to get the right answer, because that's in the book (at least I guess the book is correct - haven't checked it yet). You want good help, be good to the helpers !

    And you can only have made a trivial mistake, right ? Let's find it! Could be as simple as having you calculator on degrees instead of radians!
     
  4. Feb 4, 2014 #3
    All I done for x was

    x= 0.08sin(7.5) = 0.01m

    And the same process for v and a!

    I should say I also answered the exercise which followed using the same method and got it correct:)
     
  5. Feb 4, 2014 #4

    BvU

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    sin(7.5)=0.938
     
  6. Feb 5, 2014 #5
    AHHHHHH I see the problem!!! My calculator isn't in radians!!! Doh!!!

    Sorry for wasting your time
     
  7. Feb 5, 2014 #6

    BvU

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    Don't mind.
    1. (hopefully) you learned something in working on this kind (and other kinds) of exercise
    2. If you get stuck again, you will probably make things easier for potential helpers (they will be happy and you'll get more, quicker, better help).
    That's what PF is for, so I'm not convinced time was wasted.
     
  8. Feb 5, 2014 #7
    Thanks:)
     
  9. Feb 5, 2014 #8

    BvU

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    :shy:Don't thank me: hit the button! Who knows I might get a promotion out of this....
     
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