MACHINES 



59 



The best way to measure the force is to take the mean 

 of the force which will just cause the weight to ascend 



A. B. Block and tackle. 



FIG. 53. A Common Way of Arranging Pulleys for Lifting Heavy Weights. 



slowly and that which will just cause it to move down 

 slowly. 



EXERCISES 



1. Draw a diagram of pulleys arranged so that 50 pounds will 

 support 100 pounds. 



2. Hay is sometimes carried from the wagon to the mow. Can 

 you arrange a set of four pulleys to do this? 



Wheel and Axle. Figure 54 shows a diagram of a 

 simple form of the wheel and axle. If the radius OA of 

 the wheel is four times the radius OC of the axle, then 

 one pound of force will support four pounds of weight 

 on the axle. Of course if the radius of the wheel is four 



