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Homework Help: Energy problem

  1. Mar 1, 2005 #1
    Assuming an energy equivalent for your food of 2.1 x 107 J/kg, calculate the amount of food needed to walk a distance of 30 km at a rate of 5 km/hr?
  2. jcsd
  3. Mar 1, 2005 #2
    You can't answer that one without more information.

    You need to know how many watts of power (joules per second) the person uses when walking at that speed.

    Travelling at a constant speed needn't use any energy at all (unless it is uphill, or against some resisting force). Obviously a walking person does use energy to do so, but without knowing the rate of energy usage (power) then there is no way to answer the question.
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