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Homework Help: Elliptical Orbit

  1. Mar 19, 2006 #1
    A partical is moving in a elliptical orbit with uniform speed. How can I tell whether there are tangential and normal acceleration or not on the partical? (At A B and C )


    thanks for help!
     

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  3. Mar 19, 2006 #2

    siddharth

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    You can show your work for a start.
     
  4. Mar 19, 2006 #3
    I think I figure it out.
    Since it's speed is constant, there's is no change in tangential velocity, hence tangential acceleration remain zero.
     
  5. Mar 19, 2006 #4

    Hootenanny

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    That's correct. :smile: Now what about the normal acceleration?
     
  6. Mar 19, 2006 #5

    Hootenanny

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    Ahh yes, I suppose constant magnitude would be an accurate term. Just re-reading through the question (and without looking at the picture obviously), I can't see the point. There is always going be tangental acceleration, and there also must always be normal acceleration, although this will change. :confused:
     
  7. Mar 19, 2006 #6

    siddharth

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    What I posted first wasn't exactly correct

    What I mean is, if
    [tex] \vec{r} = r \vec{e_r} [/tex]

    then according to the OP's question,
    [tex] |\frac{d\vec{r}}{dt}| [/tex] will be constant. So, for an ellipse, this doesn't mean that [tex] \frac{d^2\vec{r}}{dt^2} [/tex] along [tex] e_\phi [/tex] will be 0.

    In fact, for a circular orbit, since [tex] \frac{dr}{dt} =0 [/tex], the tangential acceleration will be 0.
     
    Last edited: Mar 19, 2006
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