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Homework Help: Uniform circular motion and coordinate system

  1. Jun 21, 2008 #1
    2. In the figure below the particle P is in uniform circular motion. The motion is centered on the origin of an xy coordinate system.
    (a) At what values of [tex]\vartheta[/tex] is the vertical component r[tex]_{y}[/tex] of the position vector greatest in magnitude?
    (b) At what values of [tex]\vartheta[/tex] is the vertical component v[tex]_{y}[/tex] of the particle’s velocity greatest in magnitude?
    (c) At what values of [tex]\vartheta[/tex] is the vertical component a[tex]_{y}[/tex] of the particle’s acceleration greatest in magnitude?

    a. How can radius have a vertical component? It's just a distance or would it be a displacement?

    b. Isn't velocity always tangential to the circle so how would there be a y component? Or does he just mean when it points in the y direction like at zero and 180 degrees?

    c. Would it be 90 degrees and 270 because it only has a vertical component?

    Any help would be appreciated
     
  2. jcsd
  3. Jun 21, 2008 #2
    The figure is in my gravitational force post. I don't know how to move it. It's question 2.
     
  4. Jun 21, 2008 #3

    G01

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    You have the basic idea correct. The magnitude of the y component of each vector is greatest when the whole vector lies along the y-axis. So, your answers to b) and c) are correct.

    For part a) you are working with a position vector, not just a distance. The radial position vector points outward from the origin toward the object. Can you answer part a) now?
     
  5. Jun 21, 2008 #4
    Yea I can answer it now. I just didn't know it was a vector thought it was just a scalar. Shouldn't it just be at 90 degrees and 270 again?
     
  6. Jun 21, 2008 #5

    G01

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    You got it.:smile:
     
  7. Jun 21, 2008 #6
    Thanks for the help
     
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