60 



GENERAL SCIENCE 



times the circumference of the 

 axle, the force F will move four 

 times as far as the weight W, or 



Weight X distance through which it 

 moves 



= Force X distance through 

 which it moves. 



In the windlass, which is a 

 common form of the wheel and 

 axle, a crank takes the place of 

 the wheel (Figure 55). The 

 principle, however, is exactly the 

 same. Figure 56 shows how 

 two machines of the wheel-and-axle type may be com- 

 bined to lift enormous weights. 



EXERCISES 



1. Name three uses of the wheel and axle. 



2. The radius of a wheel is 2 feet and that of the axle 4 inches. 

 What force will be required to overcome a weight of 600 pounds? 



FIG. 54. Wheel and Axle. 



FIG. 55. Tiie Windlass. 



3. What kind of machine is a capstan? A coffee grinder? A 

 bicycle pedal? 



