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Homework Help: The energy required by a fish swimming at speed v to travel a distance

  1. Jan 19, 2012 #1
    The energy required by a fish swimming at speed v to travel a distance L>0 in a current of speed u>0 is given by

    E(v) = aL((v^3)/(v-u)), v>u

    where a>0 is a proportionality constant.
    a) Find the speed of the fish which results in minimal energy expenditure.
    b) Give a qualitative sketch of the energy as a function of the speed of the fish.

    I know that I am supposed to isolate v from the equation by using another equation in order to differentiate it, but I don't know how to. As well as a is a constant, and all values are positive. Also when I am drawing the sketch will the value a still be included? How do I include this in a graph?
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution
    Last edited by a moderator: Jan 19, 2012
  2. jcsd
  3. Jan 19, 2012 #2


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    Homework Helper

    Re: Optimizing

    Why? If you want to minimize the function E(v) you need to differentiate E with respect to v and find out where it is zero.
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