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Homework Help: Need help with a problem involving work and calories!

  1. Dec 14, 2012 #1
    1. The problem statement, all variables and given/known data
    A person whose mass is 70 kg runs up a flight of stairs through a vertical height of 6 m. If she uses her food with an efficiency of 10%, how many food calories does she have to consume to do this work?

    2. Relevant equations


    (Output/input)*100 = Efficiency
    3. The attempt at a solution

    I assumed that mgh=w because there is not kinetic energy at the top, so I just solved for mgh and got 4116J. I converted that into calories and found the input using the formula above, an I got ~9830 cals. When I looked at the answer key it said 9.9 cals( not Kcals)
  2. jcsd
  3. Dec 15, 2012 #2


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    Staff Emeritus
    Science Advisor
    Homework Helper

    A food calorie is a Kcal. (You can look it up.)
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