(II) Refrigeration units can be rated in “tons.” A 1-ton air conditioning system can remove sufficient energy to freeze 1 British ton (2000 pounds = 909 kg) of 0°C water into 0°C ice in one 24-h day. If, on a 35°C day, the interior of a house is maintained at 22°С by the continuous operation of a 5-ton air conditioning system, how much does this cooling cost the homeowner per hour? Assume the work done by the refrigeration unit is powered by electricity that costs $0.10 per kWh and that the unit’s coefficient of performance is 15% that of an ideal refrigerator. 1 kWh = 3.60 × 10 6 J.
(II) Refrigeration units can be rated in “tons.” A 1-ton air conditioning system can remove sufficient energy to freeze 1 British ton (2000 pounds = 909 kg) of 0°C water into 0°C ice in one 24-h day. If, on a 35°C day, the interior of a house is maintained at 22°С by the continuous operation of a 5-ton air conditioning system, how much does this cooling cost the homeowner per hour? Assume the work done by the refrigeration unit is powered by electricity that costs $0.10 per kWh and that the unit’s coefficient of performance is 15% that of an ideal refrigerator. 1 kWh = 3.60 × 10 6 J.
(II) Refrigeration units can be rated in “tons.” A 1-ton air conditioning system can remove sufficient energy to freeze 1 British ton (2000 pounds = 909 kg) of 0°C water into 0°C ice in one 24-h day. If, on a 35°C day, the interior of a house is maintained at 22°С by the continuous operation of a 5-ton air conditioning system, how much does this cooling cost the homeowner per hour? Assume the work done by the refrigeration unit is powered by electricity that costs $0.10 per kWh and that the unit’s coefficient of performance is 15% that of an ideal refrigerator. 1 kWh = 3.60 × 106 J.
(g) A 2 kW kettle containing 1.5 kg of water at 15°C is switched on for 5 minutes.
i. How much heat energy is transferred?
ii. What will be the temperature rise of the water? (Cwater = 4.2k] kg-1 K-')
iii.
What is the final temperature of the water?
(a) Suppose you start a workout on a Stairmaster, producing power at the same rate as climbing 116 stairs per minute. Assuming your mass is 76.0 kg and your efficiency is 20.0 how long will it take for your body temperature to rise 1.00ºC if all other forms of heat transfer in and out of your body are balanced? (b) Is this consistent with your experience in getting warm while exercising?
(II) The heat capacity, C, of an object is defined as the amount
of heat needed to raise its temperature by 1 C°. Thus, to
raise the temperature by AT requires heat Q given by
Q = CAT.
(a) Write the heat capacity C in terms of the specific heat, c,
of the material. (b) What is the heat capacity of 1.0 kg of
water? (c) Of 45 kg of water?
Chapter 20 Solutions
Physics for Scientists and Engineers with Modern Physics
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The Laws of Thermodynamics, Entropy, and Gibbs Free Energy; Author: Professor Dave Explains;https://www.youtube.com/watch?v=8N1BxHgsoOw;License: Standard YouTube License, CC-BY