Page 237 - Schaum's Outline of Theory and Problems of Applied Physics

222 HEAT [CHAP. 18

18.19. Ten kilograms of ice at 0 C is mixed with 2 kg of steam at 100 C. Find the temperature of the resulting water.
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18.20. Three thousand Btu of heat is added to 3 lb of water at 100 F. How much steam is produced? What is the temperature
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of the steam?
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18.21. River water at 10 C is used to condense spent steam at 120 C to water at 50 C in an electric generating plant. If the
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cooling water leaves the condenser at 30 C, how many kilograms of river water are needed per kilogram of spent
steam?
18.22. (a) How many kilocalories per hour are given off by a 100-W light bulb? (b) How many Btu per hour?
18.23. A typical gumdrop contains 35 kcal of energy. If this energy were used to raise an 80-kg person above the ground,
how high would that person go?

18.24. A lead bullet traveling at 200 m/s strikes a tree and comes to a stop. If half the heat produced is retained by the bullet,
by how much does its temperature increase [c lead = 0.13 kJ/(kg· C)]?
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18.25. Some 1.5 kg of water at 10 C in a 300-g aluminum kettle is placed on a 2-kW electric hot plate. What is the
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temperature of the water after 3 min [c aluminum = 0.92 kJ/(kg· C)]?

Answers to Multiple-Choice Questions

18.1. (d) 18.9. (c)

18.2. (c) 18.10. (b)

18.3. (b) 18.11. (b)
18.4. (c) 18.12. (b)

18.5. (b) 18.13. (b)

18.6. (a) 18.14. (d)

18.7. (b) 18.15. (d)

18.8. (c) 18.16. (b)

Answers to Supplementary Problems

18.1. The kinetic energy of the moving water becomes dissipated into internal energy, and the water therefore has a higher
temperature than before it was stirred.

18.2. The ice absorbs heat from the drink in order to melt to water at 0 C.
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18.3. −173 F; 172 F 18.5. 600 Btu
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18.4. −7 C; 60 C 18.6. 586 kJ
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