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DV/dS*v = a

  1. Jan 8, 2013 #1
    dV/dS*v=a
    now at the higest point when we throw a ball.
    v=0
    which implies a=0

    but that is npot true....any expanations?
     
  2. jcsd
  3. Jan 8, 2013 #2

    tiny-tim

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    welcome to pf!

    hi carhah! welcome to pf! :smile:
    no, v= 0 does not imply dv/dt = 0 :wink:

    (draw a graph of v against t)
     
  4. Jan 8, 2013 #3
    Re: dV/dS*v=a

    but if we put v=0 in equation-dV/dS*v=a

    we get a=0?

    i am in doubt...
     
  5. Jan 8, 2013 #4
    Re: welcome to pf!


    but if we put v=0 in equation-dV/dS*v=a
     
  6. Jan 8, 2013 #5

    tiny-tim

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    hi carhah! :smile:

    (you don't need to send a pm … everyone gets automatic email notification of any new post in any thread they've posted in :wink:)
    but dv/ds = ∞ (draw the graph of v against s)

    eg, if a is constant, and if so = vo = 0, then s = 1/2 at2 and v = at,

    so v = √(2as), so dv/ds|t=0 = √(a/so)= √(a/0) = ∞ :wink:
     
  7. Jan 8, 2013 #6
    Re: dV/dS*v=a




    thanks tim :D
    BUT DOES that mean that we cannot apply that formula a=dv/ds*v in case of constant acceleration. :)
     
  8. Jan 8, 2013 #7

    tiny-tim

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    no, you can always apply that formula …

    but if it says a = ∞*0, that doesn't help very much! :wink:
     
  9. Jan 8, 2013 #8
    Re: dV/dS*v=a

    can u draw graph of dv/ds ? and prove it is infinity?
     
  10. Jan 8, 2013 #9

    tiny-tim

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    you can draw a graph of v against s (as i've already asked you to) …

    where it's vertical, dv/ds = ∞​
     
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