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Net work W calculus

  1. Oct 13, 2011 #1
    In the equation:


    I just don't understand how the 3rd part of the equation is changed into the 4rth (Dt going under the Dx). If I can get some help with this, that would be great.

    The way I think about it is [m*Δv/Δt]Δx = mΔx(Δv/Δt)

    I have no idea how Dt went under the Dx...
  2. jcsd
  3. Oct 13, 2011 #2


    Staff: Mentor

    It's no different from writing
    [tex]\frac{3}{4}\cdot 5 = 3\cdot \frac{5}{4}[/tex]
  4. Oct 14, 2011 #3


    User Avatar
    Science Advisor

    Note that [itex]\Delta x[/itex], [itex]\Delta v[/itex], and [itex]\Delta t[/itex] are numeric approximations to the differentials, not the differentials. They are simply numbers and what is going on is simply manipulation of numbers.
    [tex]a\frac{b}{c}= \frac{ab}{c}= \frac{ba}{c}= b\frac{a}{c}[/tex]
  5. Oct 14, 2011 #4
    Ah thank you. I couldn't see it for some reason...
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