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Homework Help: Animal Foraging Radius Equation Part 2

  1. Nov 30, 2012 #1
    1. The problem statement, all variables and given/known data

    I asked a similar question before relating to an animal's foraging radius. I think there was a typo but I'd like to show another example to see if I'm on the right track.

    The parameter values are as follows:

    Q= 5.2 × 106 J
    C = 1.5kg
    d= 0.055kg per hour
    k= 2.0 Joules/m
    Ema = 24 Watts
    Emc = 42 Watts
    T = 48 hours
    v= 45km per hour
    t= 12 hours

    2. Relevant equations

    r = [QC +Qdt - T(Ema+Emc/2)/(2k+ (2Qd/v))]

    3. The attempt at a solution

    (7800000 + 5.2*10^6*.055*12 - 172800 (45))/16.711111111111112
  2. jcsd
  3. Nov 30, 2012 #2


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    A minor point is that it would be good practice to group the first two numerator terms as
    Q(C + DT). One less arithmetical operation to do and error risked. Similarly you could take out the factor 2 in the denominator

    More important is you must pay constant attention to units. E.g.you do not give a unit for your result - metres or Km...

    It seems there is something wrong about your physical units, maybe misquotation of formulae or units? The expression I just gave is JoulesXKg. The way you have written the equation they appear as such in the result which is nonsense - you must get a distance. The denominator has a similar anomaly and you would be adding things of incompatible dimensions - it is probably the second term that is wrong.
  4. Dec 2, 2012 #3


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    (I see I drew attention to the same units and dimensions issue in your previous thread.)
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