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Can someone tell me why this integral is invalid?

  1. Nov 16, 2012 #1
    Hey guys,

    Can someone tell me why this integral isn't valid?

    ∫ v Δp = pv + C
     
  2. jcsd
  3. Nov 16, 2012 #2

    Mark44

    Staff: Mentor

    You're treating v as if it were a constant.

    This is valid:

    $$ \int k~dx = kx + C$$

    This is not:
    $$ \int f(x)~dx = f(x) \cdot x + C$$
     
  4. Nov 17, 2012 #3
    Basically, [itex]\displaystyle \int y\,dx = yx + C \text{ iff }\frac{dy}{dx} = 0[/itex].
     
  5. Nov 17, 2012 #4

    Mark44

    Staff: Mentor

    Which is the same as saying y is a constant.
     
  6. Nov 17, 2012 #5
    Ah I see. Thanks guys.
     
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