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Heating by Shaking

  1. Dec 7, 2006 #1
    A physicist, upon awaking one morning to find his stove out of order, decides to boil the water for his wife's coffee by shaking it in a thermos flask. Suppose that he uses 380 cm3 of tap water at 58°F, that the water falls 1.15 ft each shake, and that the physicist completes 32 shakes each minute. Neglecting any loss of thermal energy by the flask, how long must he shake the flask before the water boils?

    Could anyone give me alittle help as to what equation to
    use for this problem?
     
  2. jcsd
  3. Dec 7, 2006 #2
    okay, assuming no thermal or mechanical losses, all of the the energy transferred from this process should be transferred into heat for the water.
    Assume a constant density, find the mass, you know c , you know a specified delta T. Remember your units here. Your usual Heat capacity that you find will be in J/(g*K). for water we know this to be 4.186. Find Q. This will be how much energy will have to be converted right? You can calculate how much energy is generated/shake. The rest should be pretty easy.
     
  4. Feb 1, 2011 #3
    I'm working on this problem too. I just was given different numbers. I have the heat required to reach the boiling point in the water as well as how much heat per shake is happening (J/shake), but I'm stuck here.
     
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