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Burning Calories by radiation (Stefan-Boltzman law)

  1. Oct 4, 2012 #1
    1. The problem statement, all variables and given/known data
    An ice cream cone has 290 Calories. Assuming the temperature of your skin is 32.7 C and the temperature of the air is 19.9 C, how long (hours) will it take to radiate away the energy of the ice cream cone. The emissivity of the average body is 0.915 and the average surface area of your skin is 1.25 m2.


    2. Relevant equations
    Stefan's law to get Watts
    P=(J/Δt)
    Q=mCΔT


    3. The attempt at a solution
    I'm all set with just plugging in the numbers into Stefan's Law to get watts, I'm having trouble trying to figure out how to get from watts to time though. All I can think of is

    P=(J/Δt)=(Q/Δt) and Q=mCΔT, but I don't have enough information to solve for Q. Any help on this?

    Thanks.
     
  2. jcsd
  3. Oct 4, 2012 #2
    You need Stefan-Boltzman law.
    What you wrote is just the definition of power (P=Energy/time) and not Stefan's law.
     
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