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GO Evaporative cooling of beverages. A cold beverage can be kept cold even on a warm day if it is slipped into a porous ceramic container that has been soaked in water. Assume that energy lost to evaporation matches the net energy gained via the
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Fundamentals of 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_forwardAn aluminum rod 0.500 m in length and with a cross sectional area of 2.50 cm2 is inserted into a thermally insulated vessel containing liquid helium at 4.20 K. The rod is initially at 3(H) K. (a) If one-halt of the rod is inserted into the helium, how many liters of helium boil off by the time the inserted half cools to 4.20 K? Assume the upper half does not yet cool, (b) If the circular surface of the upper end of the rod is maintained at 300 K. what is the approximate boil-off rate of liquid helium in liters per second after the lower half has reached 4.20 K? (Aluminum has thermal conductivity of 3 100 YV/m K at 4.20 K; ignore its temperature variation. The density of liquid helium is 125 kg/m3.)arrow_forward(a) At what temperature do the Fahrenheit and Celsius scales have the same numerical value? (b) At what temperature do me Fahrenheit and Kelvin scales have the same numerical value?arrow_forward
- A sample of a solid substance has a mass m and a density 0 at a temperature T0. (a) Find the density of the substance if its temperature is increased by an amount T in terms of the coefficient of volume expansion b. (b) What is the mass of the sample if the temperature is raised by an amount T?arrow_forward(a) An exterior wall of a house is 3 m tall and 10 m wide. It consists of a layer of drywall with an R factor of 0.56, a layer 3.5 inches thick filled with fiberglass batts, and a layer of insulated siding with an R factor of 2.6. The wall is built so well that there are no leaks of air through it. When the inside of the wall is at 22 and the outside is at 2 , what is the rate of heat flow through the wall? (b) More realistically, the 3.5-inch space also contains 2-by-4 studs—wooden boards 1.5 inches by 3.5 inches oriented so that 3.5-inch dimension extends from the drywall to the siding. They are "on 16-inch centers," that is, the centers of the studs ale 16 inches apart. What is the heat current in this situation? Don't worry about one stud mole or less.arrow_forward(a) If the partial pressure of water vapor is 8.05 torr, what is the dew point? (760 torr = I atm 101, 325 Pa) (b) On a warn day when the air temperature is 35 and the dew point is 25 , what are the partial of the water in the air and the relative humidity?arrow_forward
- In 1993, the U.S. government instituted a requirement that all room air conditioners sold in the United States must have an energy efficiency ratio (EER) of 10 or higher. The EER is defined as the ratio of the cooling capacity of the air conditioner, measured in British thermal units per hour, or Btu/h, to its electrical power requirement in watts. (a) Convert the EER of 10.0 to dimensionless form, using the conversion 1 Btu = 1 055 J. (b) What is the appropriate name for this dimensionless quantity? (c) In the 1970s, it was common to find room air conditioners with EERs of 5 or lower. State how the operating costs compare for 10 000-Btu/h air conditioners with EERs of 5.00 and 10.0. Assume each air conditioner operates for 1 500 h during the summer in a city where electricity costs 17.0 per kWh.arrow_forwardA spherical shell has inner radius 3.00 cm and outer radius 7.00 cm. It is made of material with thermal conductivity k = 0.800 W/m C. The interior is maintained at temperature 5C and the exterior at 40C. After an interval of time, the shell reaches a steady state with the temperature at each point within it remaining constant in time. (a) Explain why the rate of energy transfer P must be the same through each spherical surface, of radius r, within the shell and must satisfy dTdr=P4kr2 (b) Next, prove that 5dT=P4k0.030.07r2dr where T is in degrees Celsius and r is in meters. (c) Find the rate of energy transfer through the shell. (d) Prove that 5TdT=1.840.03rr2dr where T is in degrees Celsius and r is in meters. (e) Find the temperature within the shell as a function of radius. (f) Find the temperature at r = 5.00 cm, halfway through the shell.arrow_forwardAn aluminum rod 0.500 m in length and with a cross-sectional area of 2.50 cm2 is inserted into a thermally insulated vessel containing liquid helium at 4.20 K. The rod is initially at 300 K. (a) If one-half of the rod is inserted into the helium, how many liters of helium boil off by the time the inserted half cools to 4.20 K? Assume the upper half does not yet cool. (b) If the circular surface of the upper end of the rod is maintained at 300 K, what is the approximate boil-off rate of liquid helium in liters per second after the lower half has reached 4.20 K? (Aluminum has thermal conductivity of 3 100 W/m K at 4.20 K; ignore its temperature variation. The density of liquid helium is 125 kg/m3.)arrow_forward
- In 1986, a gargantuan iceberg broke away from the Ross Ice Shelf in Antarctica. It was approximately a rectangle 160 km long, 40.0 km wide, and 250 m thick. (a) What is the mass of this iceberg, given that the density of ice is 917kg/m3 ? (b) How much heat transfer (in joules) is needed to melt it? (c) How many years would it take sunlight alone to melt ice this thick, if the ice absorbs an average of 100W/m2, 12.00 h per day?arrow_forward(a) Find the density in SI units of air at a pressure of 1.00 atm and a temperature of 20 , assuming that air is 78% N2, 21% O2, and 1% Ar, (b) Find the density of the atmosphere on Venus, assuming that it's 96% CO2 and 4% N2, with a temperature of 737 K and a pressure of 92.0 atm.arrow_forward(a) Calculate the rate of heat conduction through a double-paned window that has a 150-m2 area and is made of two panes of 0.800 cm-thick glass separated by a 1.00 cm air gap. The inside surface temperature is 15.0 C, while that on the outside is 10.0 OC. (Hint: There are identical temperature drops across the two glass panes. First find these and then the temperature drop across the air gap. This problem ignores the increased heat transfer in the air gap due to convection.) (b) Calculate the rate of heat conduction through a 1.60-cm-thick window of the same area and with the same temperatures. Compare your answer with that for part (a).arrow_forward
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