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1. [-/1 Points] DETAILS WAUNIPHYSAV1 17.P.044. MY NOTES ASK YOUR TEACHER PRACTICE ANOTHER How many joules of heat transfer are required to thaw a 0.457-kg package of frozen vegetable juice originally at OC if its latent heat of fusion is the same as that of water (334 k]/kg)? J 2. [-/1 Points] DETAILS WAUNIPHYSAV1 17.P.046. MY NOTES ASK YOUR TEACHER PRACTICE ANOTHER A 2.63-g lead bullet traveling at 468 m/s strikes a target, converting its kinetic energy into thermal energy. Its initial temperature is 40.0C. The specific heat is 128 3/(kg . .C), latent heat of fusion is 24.5 kJ/kg, and the melting point of lead is 327.C. (a) Find the available kinetic energy of the bullet. (b) Find the heat required to melt the bullet. 3. [-/1 Points] DETAILS WAUNIPHYSAV1 17.P.048. MY NOTES ASK YOUR TEACHER PRACTICE ANOTHER Burns produced by steam at 100C are much more severe than those produced by the same mass of 100 C water. To verify this, answer the questions below. Specific heat of water = 1.00 kcal/(kg . .C); heat of vaporization = 539 kcal/kg; specific heat of human flesh = 0.83 kcal/(kg . C). (a) Calculate the quantity of heat that must be removed from 3.40 g of 100C water to lower its temperature to 42.5.C. kcal (b) Calculate the quantity of heat that must be removed from 3.40 g of 100C steam to condense it and lower its temperature to 42.5.C. kcal (c) Calculate the mass of human flesh that the quantity of heat produced in each case can raise from the normal 37.0 C to 42.5C. (Flesh is badly damaged at 50.0.C.) water kg steam kgWAUNIPHYSAV1 17.P.053. MY NOTES ASK YOUR TEACHER PRACTICE ANOTHER In some countries, liquid nitrogen is used on dairy trucks instead of mechanical refrigerators. A 100-h delivery trip requires 360 L of liquid nitrogen, which has a density of 308 kg/m3. (a) Calculate the heat needed to evaporate this amount of liquid nitrogen and raise its temperature to 458C. This is the amount of cooling the liquid nitrogen supplies. The boiling point of nitrogen is 195.8C, its specic heat CD at constant 4. [-11 Points] pressure is 0.248 kcal/(kg - C), and its latent heat of vaporization is 48.0 kcal/kg. (You must use cu, and you can assume it is constant over the temperature range.) (b) What is this in kilowatt-hours? S w - h (c) How much cooling would be obtained from melting an Identical mass of 0C Ice? The latent heat of fusion for ice ls 79.8 kcal/kg. I: kcal 5. [-11 Points] WAUNIPHYSAV1 17.P.055. ASK YOURTEACHER PRACTICE ANOTHER A large power plant heats 1377 kg of water per second to high-temperature steam to run ii: electrical generators. (a) How much heat transfer is needed each second to raise the water temperature from 650C to 100C, boil it, and then raise the resulting steam from 100C to 450C? Specic heat of water is 4184 J/(kg - C), the latent heat of vaporization of water is 2256 kJ/kg, and the specic heat of steam is 2010 J/(kg ~ C). |:l J (b) How much power is needed in megawatts? (Note: In real power plants, this process occurs under high pressure, which alters the boiling point' The results of this problem are only approximate.) MW WAUNIPHYSAV1 17.P.058. MY NOTES ASK YOUR TEACHER PRACTICE ANOTHER A glass coffee pot has a 9.00 cm diameter circular bottom in contact with a heating element that keeps the coffee warm with a continuous 50.0-W heat input' 6. [-11 Points] (a) What is the temperature of the bottom of the pot, if it is 150 mm thick and the inside tempelature is 503C? The thermal conductivity of the pot is 0.841/(5 - m ' C). |:l \"'6 (b) If the temperature of the coffee remains constant and all of the heat input is removed by evaporation, how many grams per minute evaporate? Take the latent heat of vaporization to be 560 cal/g. 9 WAUNIPHVSAV1 17.P.065. ASK YOUR TEACHER PRACTICE ANOTHER The rate of heat conduction out ofa window on a winter day Is rapid enough to chill the air next to It. To see just how rapidly windows conduct heat, calculate the rate of conduction In watts through a 2.62 m2 window that is 0.695 cm thick if the temperatures of the inner and outer surfaces are 500C and 10.0C, respectively. This rapid rate will not be maintained - the Inner surface will cool, and frost may even form. The thermal conductivity of glass ls 0.84 J/(s ~ rn ~ C). 1:]W 1. [-/1 Points] ASK YOUR TEACHER PRACTICE ANOTHER A one-story house is heated with natural gas, which gives off 3.890 X 107] of energy for every cubic meter of gas burned. Take the average temperature difference between the inside and outside for the 120-day heating season to be 12C. In the diagram below h; = 5.00 m, W = 8.00 rn, L = 10.0 m and h; = 3.00 m. 8. [-I1 Points] WAUNIPHVSAV1 17.P.070.TUTORIAL. (a) If the walls, windows, and roof have an average thickness of 22.0 cm and the thermal conductivity (including the windows) is 0.48 W/(m ~ C), determine how many cubic meters of gas is used up during the 120-day winter season? Assume air inltration and heat loss through the ground is negligible. 2 "'3 (b) Many decisions are made on the basis of the payback period: the time it will take through savings to equal the capital cost of an investment. Acceptable payback times depend upon the business or philosophy one has. (For some industries, a payback period is as small as two years.) Suppose you wish to install an extra 8 cm ofberglass to the roof. If energy costs $0.90 per one hundred million joules and the insulation was $4.00 per square meter, then calculate the simple payback time taking the 120day heating season to be equivalent to one yean |:ivr @ Tnlorlll WAUNIPHYSAV1 17.P.071 . ASK YOUR TEACHER PRACTICE ANOTHER In the diagram below, metal 1 is made of copper and metal 2 is aluminum. Both bars have the same length and area of cross-section but their thermal conductivities are different. The temperature Th is maintained at a constant 900C at the end A while 9. [-l1 Polnts] the temperature Tc at the end B is maintained at 343C. (a) What is the temperature T,- at the junction of the two bars? The thermal conductivity of copper is 3901/(5 - m . C) and that for aluminum is 220 J/(s - m - C). 2 C (b) If metals 1 and 2 are now interchanged, but the values of Th and Tc are the same as in part (a), what will be the temperature of the junction? E\" ASK YOUR TEACHER 10. [-I1 Points] WAUNIPHYSAV1 17.P.075.TUTORIAL. The Sun radiates like a perfect blackbody with an emissivity of exactly 1. (a) Calculate the surface temperature of the Sun, given it is a sphere with a 7.00 x 103 m radius that radiates 3.80 x 1026 w into 3 K space. E K (b) How much power does the Sun radiate per square meter of its surface? :l W (c) How much power In watts per square meter is this at the dlstance of the Earth, 1.5!) x 1011 m away? (This number is called the solar constant.) me 93 \"Mel