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Terminal speed

  1. Mar 23, 2004 #1
    fluid resistance

    how to know the fluid resistance is depend on [tex] v [/tex] or [tex] v^2 [/tex] ??
    Last edited: Mar 23, 2004
  2. jcsd
  3. Mar 23, 2004 #2


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    Are you asking why fluid resistance is velocity dependent? Or are you asking how to determine whether the dependence goes linear or whether it goes quadratic with velocity?
  4. Mar 23, 2004 #3
    Re: fluid resistance

    Well, you could look it up. Or you could run some experiments. A simple experiment might use a tub or water and a submerged block of wood, with a spring or rubber band providing a measurable force to move the block, and a stopwatch.

    Experiments in the tub are always fun.
  5. Mar 23, 2004 #4
    I'm going to guess it depends on [tex]v^1[/tex]... let us know when you find out. :smile:
  6. Mar 25, 2004 #5
    It is almost certainly a power series expansion in powers of velocity, with the linear term being the most important contributor. In other words:

    [itex] F(v) = a v + bv^2 + cv^4 + ...[/itex]

    It would be a fun experiment to determine a, b, c,...
  7. Mar 25, 2004 #6
    The [tex]v^2[/tex] in the formula for turbulent current is an energy thing: the kinetic energy of the fluid whirls goes with [tex]v^2[/tex], and energy equals force times deplacement.
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