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Chemical energy in the runner's body

  1. Apr 9, 2009 #1
    So I got back a test and one of the questions was the following: A person is running at a constant speed on level ground. Chemical energy in the runner's body is being transformed to other forms of energy: most of the chemical energy is transformed to?
    a. thermal energy
    b. potential energy
    c. kinetic energy

    I chose kinetic energy but the correct answer is thermal. Do anyone know how to explain why?
     
  2. jcsd
  3. Apr 9, 2009 #2
    Re: Energy

    I probably would have chosen kinetic as well, but thermal makes sense, because alot of human's energy is wasted by becoming heat rather than kinetic.
     
  4. Apr 9, 2009 #3

    LowlyPion

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    Re: Energy

    Well ... it's not up hill ... there goes potential energy as a possibility.
    There is no change in velocity ... so there goes any change in kinetic energy.
     
  5. Apr 9, 2009 #4
    Re: Energy

    That is a bad question. There are various forms of energy in that given situation. Both A and C are correct.

    There's heat transfer going on between the body and the ambient environment. However, there's electrical energy, kinetic energy, and chemical energy involved, as well.

    Muscular movement is a combination of electrical signals and chemical motion (Through Fickian diffusion and biological motors).

    Muscular movement results in kinetic energy.


    EDIT: But Lowly, it doesn't say if there's change in KE. It just says what is the energy being transformed to. The change in KE could be 0, but there's KE.
     
  6. Apr 9, 2009 #5
    Re: Energy

    Thank you all!
     
  7. Apr 9, 2009 #6

    LowlyPion

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    Re: Energy

    For this kind of question I don't think it matters. Whatever the internal energies of the system, the pumping of the arms and pounding of the legs, the impact of the shoes, muscles pulling tendons and bones about, the kinetic energy converts to thermal energy readily enough. For the kind of introductory question it is, I'm sure there is no intent to get esoteric about chemical/biological processes.

    Besides, I suspect when viewed over a complete stride it is mostly thermal after accounting for the energy state changes.
     
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