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How do I find the instantaneous acceleration for a velocity-time graph that is NOT a

  • Thread starter welai
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http://i52.tinypic.com/95zrsw.png

^ okay, if my velocity-time graph looks like that (it was a quick sketch), and I need to find the INSTANTANEOUS velocity at point A and point B, how do I do it?

I mean, I understand the slope of the tangent = instantaneous acceleration, but this is not a curve. Thus, I also understand to use the normal straight slope. But I don't understand, WHICH slope is the INSTANTANEOUS acceleration for those points?
 

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  • #2
Ray Vickson
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http://i52.tinypic.com/95zrsw.png

^ okay, if my velocity-time graph looks like that (it was a quick sketch), and I need to find the INSTANTANEOUS velocity at point A and point B, how do I do it?

I mean, I understand the slope of the tangent = instantaneous acceleration, but this is not a curve. Thus, I also understand to use the normal straight slope. But I don't understand, WHICH slope is the INSTANTANEOUS acceleration for those points?
You read the instantaneous velocities at A and B directly from the graph (because your plot is v vs. t). On the other hand, if you meant to say instantaneous "acceleration" (not velocity), then at A and B there is *no well-defined value*: the acceleration changes instantly from one constant value to another, so the acceleration at one 100 billionth of a second before A is different than the acceleration at one 100 billionth of a second after A.

RGV
 
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You read the instantaneous velocities at A and B directly from the graph (because your plot is v vs. t). On the other hand, if you meant to say instantaneous "acceleration" (not velocity), then at A and B there is *no well-defined value*: the acceleration changes instantly from one constant value to another, so the acceleration at one 100 billionth of a second before A is different than the acceleration at one 100 billionth of a second after A.

RGV
Thank you! Just another simple question, then would it be easier if I make a scatter-plot of my velocity points on my vt graph, then I'll find the line of best fit for average velocity, then find the instantaneous acceleration at the time interval of A and B?
 

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