Solve: so and Reflect: For water, A small mass of steam melts a larger mass of ice and also raises the temperature of the water. 14.82. Set Up: Neglect the effect of the increase in thickness of the ice on the rate of heat conduction, so H remains constant. For water, Consider an area A of ice. Ice has density The thermal conductivity of ice is Solve: The mass of the 2.00 mm thickness of ice is The amount of heat conducted through the ice in time t is Therefore, and 14.83. Set Up: The emissivity of a human body is taken to be 1.0. In the equation for the radiation heat current the temperatures must be in kelvins. Solve: (a) (b) The person gains 87.1 J of heat each second by radiation. (c) The total excess heat per second is (d) In the runner must dispose of If this much heat goes to evap-orate water, the mass m of water that evaporates in one minute is given by so (e) In a half-hour, or 30 minutes, the runner loses The runner must drink 0.84 L, which is Reflect: The person gains heat by radiation since the air temperature is greater than his skin temperature. 14.84. Set Up:
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