MACHINES 



61 



4. If a bicycle pedal is 7 inches long and the radius of the 

 sprocket wheel is 3^ inches, what pull will be exerted on the sprocket 

 wheel by a force of 50 pounds on the pedal ? 



The Inclined Plane. Arrange a board as shown in 

 Figure 57, so that it makes an angle of 20 or 30 degrees 



with the table. In the absence 

 of a carriage, a roller skate may 

 be used. Find the mean of the 

 force at F that will just cause 

 the carriage to move up the in- 

 cline slowly, and that will just 

 cause it to move down the in- 

 cline slowly. Then 



F X length of incline (I) 

 = W X height of plane (h) 



FIG. 56. -A Combination of Tn e inclined plane is used in 

 wheels and Axles to Lift Heavy loading all sorts of heavy mate- 



Weights - -i j j. i An- 



nals on cars and trucks. When 



the objects to be loaded are round, such as barrels, they 

 are simply rolled on the plane. Such objects as pianos 



FIG. 57. Inclined Plane and Truck. 



