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A= dv/dt

  1. Aug 4, 2009 #1
    I see in many text that a = dv/dt implies that

    dv = a dt

    How is that possible, can anybody please explain me. As far as i know dv/dt is a symbol for derivative of v w.r.t t and not ratio between dv and dt.
  2. jcsd
  3. Aug 4, 2009 #2
    What you wrote is in differential form.
  4. Aug 4, 2009 #3


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  5. Aug 4, 2009 #4
    dv/dt is not a symbol. It is the mathematical formula for the derivative of v with respect to t. This is how one would show any derivative of a dependent variable with respect to an independent variable.
  6. Aug 4, 2009 #5
    And what did I say :-)
  7. Aug 4, 2009 #6
  8. Aug 4, 2009 #7


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    Now, WHY can we utilize at times the dv=adt formula, in particular, WHERE is it usable?


    When doing integration with the technique called substitution of variables (i.e the "inverse" of the chain rule):

    Given a=dv/dt, we have, trivially:
    But the right-hand side can, by the theorem of substitution of variables, be reformulated, giving the identity:

    Now, by IGNORING that the limits of integration actually refers to the limits of DIFFERENT variables, we "may say" that the "integrands" are equal, i.e, adt=dv!

    Thus, adt=dv should, at this stage of your education, be regarded as notational garnish (or garbage, if you like!)
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