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Elliptical Orbit

  • Thread starter brasilr9
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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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siddharth

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You can show your work for a start.
 
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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.
 

Hootenanny

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brasilr9 said:
Since it's speed is constant, there's is no change in tangential velocity, hence tangential acceleration remain zero.
That's correct. :smile: Now what about the normal acceleration?
 

Hootenanny

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siddharth said:
Is it? The direction of [tex] e_\phi [/tex] continously changes with [itex] \phi [/itex]. So, even if the speed is the same, the direction of velocity changes, doesn't it? So how can the tangential acceleration (ie, acceleration along [tex] e_\phi [/tex]) be the same?
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:
 

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.
 
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