Physics

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An 80 kg hiker climbs a 1000 m high hill at a constant speed. If the hiker's body is 25% efficient, how many kg of fat does the hiker burn in climbing the hill? Given: heat of reaction of body fat is 37000 kilo joules per kilogram.

I know that change in potential energy is 800,000. I just don't know what to do next.

  • Physics -

    m g h = increase of potential energy

    80 * 9.81 * 10^3 = 785*10^3 Joules

    785*10^3 = (1/4) total fuel energy burned
    so
    total fuel burned = 3.14 * 10^6 Joules

    3.14 * 10^6 J / 37*10^6 J/kg = .085 kg

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