Determining the Position as a Function of Time Equation

  • Thread starter jmason52
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  • #1
jmason52
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In simple harmonic motion of a spring, the Position as a Function of Time Equation is: x(t) = Acos(wt+phi). How does one determine whether to use "cos" or "sin" when setting up the basic equation from the data given in a problem? Is it as simple as: use "sin" when x starts at equilibrium position (0), otherwise use "cos"? Can one of you offer me a simple clarification? Thanks!
 

Answers and Replies

  • #2
rock.freak667
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I believe it has to do with where it starts as you say. If it starts at the maximum point , you use cosine, if at 0 then sine.
 
  • #3
gneill
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You might consider using whichever makes the phase angle phi a nice value (magnitude, sign). Basically it's a matter of aesthetics unless some other part of the system under analysis forces your hand.
 

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