1. If coal costs $4.00 a ton, and gas, $0.80 per 1000 cu. ft. what amounts of heat can be secured from 1 cent's worth of each? 2. What will it cost to heat 30 gallons of water (1 gal. of water weighs about 8-1/3 lbs.) from 40°F. to 190°F. with coal costing $4.00 per ton and yielding 12,000 B.T.U. per lb. if the heater has an efficiency of 50 per cent. 3. What will it cost to heat 30 gallons of water from 40°F. to 190°F. with gas at $0.80 per 1000 cu. ft. if the heating device has an efficiency of 75 per cent. 4. Construct a cardboard working-model showing the action of the gas engine and be prepared to explain the action of the various parts. 5. If 500 lbs. of iron should fall 2000 ft. and all of the resulting mechanical kinetic energy should be transformed into heat, what would be the amount of heat produced? 6. What are the special advantages of (a) the gasoline engine? (b) the turbine? (c) the reciprocating steam engine? 7. Do you burn coal or gas in your kitchen stove at home? Which is for you the more economical? Why? 8. What are the advantages of using a fireless cooker? 9. What is the efficiency of a locomotive that burns 3.2 lbs. of coal per horse-power-hour? 10. A gas engine developed in a test 0.34 horse-power for 1 minute. and 50 seconds, 0.5 cu. ft. of gas being used. The heat of combustion of the gas was 600 B.T.U. per cu. ft. Find the efficiency of the engine. 11. Find the horse-power of an engine, the diameter of the piston being 19 in., stroke 26 in.; it uses steam at an average pressure of 200 lbs. per square. inch and makes 100 strokes a minute. 12. What is the efficiency of an engine and boiler that develops 200 horse-power, while burning 390 lbs. of soft coal per hour? 13. If a locomotive has an efficiency of 6 per cent. and develops 1700 horse-power how much coal is burned in an hour? 14. If an automobile engine burns 1 gallon of gasoline in an hour and develops 10 horse-power, what is its efficiency? 15. The A.L.A.M.[J] formula for horse-power is (_N_ _B_²)/2.5 when the piston speed is 1000 ft. per minute, _N_ being the number of cylinders and _B_, their diameter. Find the horse-power of a 4-cylinder engine, the cylinders having a diameter of 4 in. [J] American League of Automobile Manufacturers. 16. Find the horse-power of a 6-cylinder automobile engine, if the cylinder diameter is 4.5 in. 17. A 4-cylinder automobile having 4-in. cylinders, uses 1 gallon of gasoline in 1 hour. Find its efficiency, if its average horse-power developed is 6. 18. The motor boat Disturber III, has 24 cylinders each with diameter 3.5 in. If the piston speed is 1000 ft. per minute, what is the horse-power? (See problem 15.) Review Outline: Heat Heat; sources (4), effects (5), units (2). Temperature; thermometer scales (3), absolute temperature, 9C°/5 + 32° = F°. Expansion; gases, Law of Charles (V_{1}/V_{2} = T_{1}/T_{2}), liquids, peculiarity of water, solids, coefficient of expansion, uses, results.