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Homework Help: Power dissipation

  1. Oct 22, 2008 #1
    1. The problem statement, all variables and given/known data

    2. Relevant equations


    3. The attempt at a solution

    why isn't it

    P = Cd(A^2)(v^2) * (v)

    i dont see what i could do

    Attached Files:

  2. jcsd
  3. Oct 23, 2008 #2

    Doc Al

    User Avatar

    Staff: Mentor

    This is correct.

    But this is not. You made an error when you substituted for F in the power equation. Redo it, paying attention to each factor in the drag formula.
  4. Oct 23, 2008 #3
    ok i figured out the first part

    how do i figure out part B?

    I kno the power is proportional to v^3
    and so if i increase the power by 10%
    i should get


    if Pi = -(vi^3)AC_d

    then 1.1Pi=-(vf^3)AC_d

    Pi = (-(vf^3)AC_d ) / 1.1

    (vf^3) = 1.1(vi^3)

    then what?

    Attached Files:

  5. Oct 23, 2008 #4

    Doc Al

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    Staff: Mentor

    Solve for Vf in terms of Vi. (Take the cube root of both sides.)
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