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Homework Help: Heat and temperature

  1. Feb 8, 2004 #1
    I'm stuck on a few problems that I was assigned for homework. Not sure if someone can help me with these...

    1) Blood can carry excess energy from the interior to the surface of the body, where the energy is dispersed in a number of ways. While a person is exercising, 0.645 kg of blood flows to the surface of the body and releases 1860 J of energy. The blood arriving at the surface has the temperature of the body interior, 37.3 °C. Assuming that blood has the same specific heat capacity as water, determine the temperature in degrees Celsius of the blood that leaves the surface and returns to the interior.

    2) If the price of electrical energy is 0.174 dollars per kilo-watt hour, what is the dollar cost of using electrical energy to heat the water in a swimming pool (13.3 m x 11.3 m x 1.93 m) from 11.3 to 26.9 °C?

    I know that the amount of heat needed to heat the water is 2.3x10^7 J and that one kilowatt per hour = 3.60x10^6 J. Which means that the number of kilowatthours of energy used to heat the water is 6.4 kwH. Just not sure what equation to use for the size of the swimming pool and the temp difference

    3) When resting, a person has a metabolic rate of about 2.34 x 105 joules per hour. The person is submerged neck-deep into a tub containing 1.81 x 103 kg of water at 26.8 °C. If the heat from the person goes only into the water, find the water temperature in degrees Celsius after half an hour.
  2. jcsd
  3. Feb 8, 2004 #2
    Ahhhh forget number 2...I think I know where I went wrong there. Copied down the wrong numbers.
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