FARM MECHANICS. 151 



is 150 pounds to develop 1 horsepower? Two-thirds of 1 

 horsepower ? 



511. What power is necessary, assuming no loss, to 

 raise grain in an elevator to a height of 40 feet at the rate 

 of one-half ton a minute? Five thousand bushels an 

 liour ? 



512. A farmer desires to fill a water tank 60 feet higli. 

 W hat horsepower engine will be necessar}' if the water In 

 raised at the rate of 210 gallons a minute? (One gallon 

 of water weighs 85^ pounds.) 



HORSE .3% 



MAN 3.5" 



Relative Cost of Power When Supplied by Horse and by Man. 



513. In the above problem what power will be re- 

 quired if 50 per cent is lost in friction? 



To keep a weight of one ton moving vertically upward 

 at a given speed requires 2,000 pounds of force. 



To keep a ton moving horizontally at a given speed on 

 an absolutely smooth or frictionless horizontal surface 

 requires no force at all. 



To keep a ton moving horizontally on a rough horizon- 

 tal surface at a given speed, requires just enough force 

 to overcome friction. 



To move a ton up a sloping surface requires more force 

 and down a sloping surface less force than along a hori- 

 zontal surface. By the use of wheels, lubricants, and im- 

 proved roadbeds, friction may be greatly reduced. On 

 the best level macadam road the total force of friction 

 or traction per ton may be as low as 30 to 50 pounds. 

 The average draft on hard level earth road with an ordi- 

 nary wagon, carrying a load of one ton, is about 150 



