236 



APPLIED SCIENCE 



one end and the distance between the supports. It makes a 

 difference which support we consider to be the fulcrum. 



If the weight were hung 

 from the center of the beam, 

 it is plain that each support 

 would carry one-half of the 

 load. But if, as shown in 

 the figure, the weight is 

 hung a distance equal to 

 one-fourth the length of the 

 beam from A , the support A 



A 



WE/GHT 



24 Ft 



FIG. 100. 



will bear three-fourths of the 

 weight and the support J5 

 will bear one-fourth. 





EXAMPLE. Suppose instead of one weight, we had two weights 

 hanging on a 1000-lb. steel beam as shown in Fig. 101. What will 

 be the pressure or weight on supports A and B f Consider one end 

 of the beam, A, as the fulcrum. Then the moment of the 6-ton 

 weight will be: 6 X 6 or 36, 

 and the moment of the 9-ton 

 weight will be: 9 X 12 or 

 "108. The moment of W, 

 the weight supported at B, 

 will be 18 X W. Then 

 since the sum of the mo- 

 ments of the weights will be 

 equal to the moment of the 

 weight supported at B, we 

 will have: 36 + 108 = 18 

 X W, or W = 8 tons, for 



the weight supported at B. But the beam itself weighs 1000 Ibs., 

 one-half of which is supported at A and the other half at B. Adding 

 this to W makes 8 tons plus % ton, or 8^ tons for the total weight 

 supported at B. The weight supported at A will, of course, be the 

 amount left after subtracting the weight at B from the total weight: 



6 tons + 9 tons + ^ ton = 15% tons, total weight 

 and 15^ tons 8J4 tons = 7% tons, the weight supported at A 



FIG. 101. 



