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One winter day, the climate control system of a large university classroom building malfunctions. As a result,
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College Physics
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- At 25.0 m below the surface of the sea, where the temperature is 5.00C, a diver exhales an air bubble having a volume of 1.00 cm3. If the surface temperature of the sea is 20.0C, what is the volume of the bubble just before it breaks the surface?arrow_forward(a) What is the rate of heat conduction through the 3.00-cm-thick fur of a large animal having a I .40-m surface area? Assume that the animal's skin temperature is 32.0 , that the air temperature is 5.00 , and that has the same thermal conductivity as air. (b) What food intake will the animal need in one day to replace this heat transfer?arrow_forwardDuring heavy exercise, the body pumps 2.00 L of blood per minute to the surface, where it is cooled by 2.00C. What is the rate of heat transfer from this forced convection alone, assuming blood has the same specific heat as water and its density is 1050kg/m3 ?arrow_forward
- The thermal conductivities of human tissues vary greatly. Fat and skin have conductivities of about 0.20 W/m K and 0.020 W/m K, respectively, while other tissues inside the body have conductivities of about 0.50 W/m K. Assume that between the core region of the body and the skin sin face lies a skin layer of 1.0 mm, fat layer of 0.50 cm, and 3.2 cm of other tissues. (a) Find the R-factor for each of these layers, and the equivalent R-factor for all layers taken together, retaining two digits. (b) Find the rate of energy loss when the core temperature is 37C and the exterior temperature is 0C. Assume that both a protective layer of clothing and an insulating layer of unmoving air a absent, and a body area of 2.0 m2.arrow_forwardA refrigerator door is opened and room-temperature air (20°C) fills the 1.50 m 3 compartment. A 10.0 kgm turkey, also at room temperature, is placed in the refrigerator and the door is closed. The density of air is 1.20 kgm/m3 and its specific heat is 1020 J / kgm °C. Assume the specific heat of a turkey, like that of a human, is 3480 J / kgm °C. How much heat must the refrigerator remove from its compartment to bring the air and the turkey to thermal equilibrium at a temperature of 5°C? Assume no heat exchange with the surrounding environment.arrow_forwardA Thermopane window of area 5 m² is con- structed of two layers of glass, each 4.4 mm thick separated by an air space of 3 mm. If the inside is at 11°C and the outside is at -24°C, what is the heat loss through the window? The thermal conductivity of glass is 0.8 W/m .° C and of air is 0.0234 W/m .° C. Answer in units of kW.arrow_forward
- In very cold weather, a significant mechanism for heat loss by the human body is the energy expended in warming the air taken into the lungs with each breath. (a) On a cold winter day when the temperature is - 20 ℃, what amount of heat is needed to warm body temperature (37 ℃) the 0.60 L of air exchanged with each breath? Assume that the specific heat of air is 1020 J/kg.K and that 1.0 L of air has a mass of 1.3 x 10-3 kg. (b) How much heat is lost per hour if the respiration rate is 20 breaths per minute?arrow_forwardA parcel of air with a volume of 9.3 x 10 km that contains 4.8 x 10 kg of water vapor rises to an altitude where all the water in the parcel condenses and then freezes. What is the change in temperature of the parcel of air due to freezing? Assume the density of air at the condensation altitude is 7.2 x 10 g/m. The specific heat of air is 0.17 cal/g Co, the latent heat of vaporization of water is 540 cal/g, and the latent heat of fusion of water is 80 cal/g.) Express the answer in standard seientific nötation. AT= x 10arrow_forwardAccording to the USDA, an average, \moderately active" college student needs to eat 2500 calories per day. These \calories" are actually kilocalories, or kcal; and, we prefer to use Joules (J) in geophysics. The conversion is 1 kcal = 4187 J. The average geothermal heat ux is 60 mW/m2. How large an area on Earth's surface releases the same amount of energy in one day as used by the average college student in a day?arrow_forward
- The world's most active volcanoes, such as the Kilauea volcano in Hawaii, can disgorge about 5 ✕ 105 m3 of 1025°C lava per day. What is the rate of heat transfer out of the earth by convection if this lava has a density of 2523 kg/m3 and eventually cools to 32°C? Assume that the specific heat of lava is the same as that of granite (840 J/(kg · °C)).arrow_forwardA glass coffee pot has a circular bottom with a 9.00-cm diameter in contact with a heating element that keeps the coffee warm with a continuous heat transfer rate of 50.0 W(a) What is the temperature of the bottom of the pot, if it is 3.00 mm thick and the inside temperature is 60.0ºC ?(b) If the temperature of the coffee remains constant and all of the heat transfer is removed by evaporation, how many grams per minute evaporate? Take the heat of vaporization to be 2340 kJ/kg.arrow_forwardA homeowner is unhappy with her heating costs. One wall of her house is 4 meters tall and 8 meters wide and has no windows, and it is made of brick and mortar with a thermal conductivity of 1.0 W m K . It is 40 cm thick. The house is heated to a temperature of 20 ◦C inside. (a) What is the rate of heat loss through the wall on a day when it is 0◦C outside? (b) A layer of rock mineral wool, which has a thermal conductivity of 0.032 W m K is to be installed on the interior surface of the brick wall. How thick should the layer be to lower the rate of heat transfer through this wall to half its original value? (c) If the rock mineral wool is instead installed on the outer surface, is the thickness required the same?arrow_forward
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