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Homework Help: Average power consumption in watts

  1. Mar 8, 2009 #1
    1. The problem statement, all variables and given/known data

    (a) If you follow a diet of 2140 food calories per day (2140 kilocalories), what is your average power consumption in watts? (A food or "large" calorie is a unit of energy equal to 4.2*10^3 J; a regular or "small" calorie is equal to 4.2 J.) Note for comparison that the power consumption in a table lamp is typically about 100 watts.
    ___ watts
    (b) How many days of a diet of 2140 large calories are equivalent to the gravitational energy change from sea level to the top of Mount Everest, 8848 m above sea level? Assume your weight is 61 kg. (The body is not anywhere near 100% efficient in converting chemical energy into change in altitude. Also note that this is in addition to your basal metabolism.)
    ____ days

    2. Relevant equations

    Power = F * v
    Power = W / delta t

    I know that 1 watt = 1 J/s

    3. The attempt at a solution

    I converted 2140 calories to Joules, which is 2140 * (4.2*10^3) = 8988000 J
    I'm not sure what I need to do from there because I can't figure out the work.

    Any help would be appreciated!
  2. jcsd
  3. Mar 8, 2009 #2


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    Homework Helper

    What is the definition of a watt?

    If you have Joules in a day, and you can figure out how many seconds are in a day ...

    As to Everest what is the potential energy increase required? m*g*h ?
  4. Mar 8, 2009 #3
    I figured it out:)

    a) (2140 cals *2400 J) / (24 days * 60 minutes * 60 seconds)

    b) (61 kg * 8848 m * 9.8 m/s) / (2140 cals *2400 J)
  5. Mar 8, 2009 #4


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    Weren't you using 4.2*10^3 J ?
  6. Mar 8, 2009 #5
    Good catch! That was a typo...I meant 4.2 * 10^3 J.

    Thanks LowlyPion:)
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