MISCELLANEOUS PROBLEMS. 529 



Measuring the power or rate of doing work. 



The rate of doing work is measured by horse-power. One 

 horse-power is the power necessary to raise 550 Ibs., one foot in 

 one second. 



PROBLEMS. 



1. How many foot-pounds can be moved by one horse-power in one 

 minute? 



2. If an engine can raise or move 66,000 foot pounds in a minute, 

 how many horse power does it have? 



3. What is the horse-power of an engine that can move 132,000 

 foot pounds in half a minute? 



Draft is the force required to pull a given weight. 

 PROBLEMS. 



1. A horse draws a load of 300 Ibs. at the rate of 4 miles per 

 hour, what horse-power is exerted? 



Solution : 



4 X 5,280 21,120 feet per hour. 

 21,120 -f- 60 = 352 feet per minute. 

 352 X 300 = 105,600 foot pounds per min. 

 105,600 -r- 33,000 = 2.12 horse-power. 



Therefore the energy exerted by this horse is 2.12 horse- 

 power. 



2. What is the horse-power of an engine that will raise 8,250 pounds 

 176 ft. in 4 minutes ? 



3. A weight of 3 tons is lifted 50 feet, (a) How much work was 

 required to lift it? (b) If the work was done in 30 seconds, what was 

 the horse-power required to do the work? 



4. How long will it take a two horse-power engine to raise 10 tons 

 100 feet? 



4. The horse-power used by English and American engineers is 

 the amount of energy which can do 550 foot-pounds of work per second 

 or 33,000 foot-pounds per minute, which is equal to 16.5 foot-tons per 

 minute; what is the horse-power required to raise 16.5 tons per minute 

 to a height of 20 feet? 



5. The English and American heat unit is the amount of heat 

 energy required to raise the temperature of one pound of pure water 

 from 32 F. to 33 F., which is 778.3 foot-pounds. How many foot- 

 pounds would be required to raise 1 ton of water 82 above 32 F.? 



NOTE One form of energy may be converted into another. 



