Hot Air in a Physics Lecture. (a) A typical student listening attentively to a physics lecture has a heat output of 100 W. How much heat energy does a class of 140 physics students release into a lecture hall over the course of a 50-min lecture? (b) Assume that all the heat energy in part (a) is transferred to the 3200 m 3 of air in the room. The air has specific heat 1020J/kg·K and density 1.20 kg/m 3 . If none of the heat escapes and the air conditioning system is off, how much will the temperature of the air in the room rise during the 50-min lecture? (c) If the class is taking an exam, the heat output per student rises to 280 W. What is the temperature rise during 50 min in this case?
Hot Air in a Physics Lecture. (a) A typical student listening attentively to a physics lecture has a heat output of 100 W. How much heat energy does a class of 140 physics students release into a lecture hall over the course of a 50-min lecture? (b) Assume that all the heat energy in part (a) is transferred to the 3200 m 3 of air in the room. The air has specific heat 1020J/kg·K and density 1.20 kg/m 3 . If none of the heat escapes and the air conditioning system is off, how much will the temperature of the air in the room rise during the 50-min lecture? (c) If the class is taking an exam, the heat output per student rises to 280 W. What is the temperature rise during 50 min in this case?
Hot Air in a Physics Lecture. (a) A typical student listening attentively to a physics lecture has a heat output of 100 W. How much heat energy does a class of 140 physics students release into a lecture hall over the course of a 50-min lecture? (b) Assume that all the heat energy in part (a) is transferred to the 3200 m3 of air in the room. The air has specific heat 1020J/kg·K and density 1.20 kg/m3. If none of the heat escapes and the air conditioning system is off, how much will the temperature of the air in the room rise during the 50-min lecture? (c) If the class is taking an exam, the heat output per student rises to 280 W. What is the temperature rise during 50 min in this case?
A cubical piece of heat-shield-tile from the space shuttle measures 0.13 m on a side and has a thermal conductivity of 0.065 J/(s·m·C°). The outer surface of the tile is heated to a temperature of 1070°C, while the inner surface is maintained at a temperature of 24°C. (a) How much heat flows from the outer to the inner surface of the tile in 4.0 minutes? (b) If this amount of heat were transferred to 2.6 liters (2.6 kg) of liquid water, by how many Celsius degrees would the temperature of the water rise?
Consider a flat-plate solar collector placed on the roof of a house. The temperatures at the inner and outer surfaces of the glass cover are measured to be 33°C and 31°C, respectively. The glass cover has a surface area of 2.5 m2, a thickness of 0.6 cm, and a thermal conductivity of 0.7 W/m·K. Heat is lost from the outer surface of the cover by convection and radiation with a convection heat transfer coefficient of 10 W/m2·K and an ambient temperature of 15°C. Determine the fraction of heat lost from the glass cover by radiation.
A silver kettle weighs 1.07 kg. (The specific heat of silver is 0.235 J/g·°C)
(a) What is the heat capacity (in J/°C) of the kettle?
_____ J/°C
(b) How much heat (in J) is required to increase the temperature of this kettle from 20.5°C to 98.7°C?
_____ J
(c) How much heat (in J) is required to heat this kettle from 20.5°C to 98.7°C if it contains 1.03 L of water (density of 0.997 g/mL and a specific heat of 4.18 J/g·°C across the temperature range)?
_____ J
Chapter 17 Solutions
University Physics with Modern Physics (14th Edition)
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