28 GRAPHIC STATICS 



rays in the force polygon (a), will make good intersections with the 

 forces which they replace or equilibrate. 



In the force polygon (a), P x is equilibrated by the imaginary forces 

 represented by the rays o a and b o acting as indicated by the arrows 

 within the triangle; P 2 is equilibrated by the imaginary forces repre- 



> 



(b) 



FIG. 14. 



sented by the rays o b and c o acting as indicated by the arrows within 

 the triangle ; P 3 is equilibrated by the imaginary forces represented by 

 the rays o c and d o acting as indicated by the arrows within the tri- 

 angle ; and P 4 is equilibrated by the imaginary forces o d and e o acting 

 as indicated by the arrows within the triangle. The imaginary forces 

 are all neutralized except a o and o e, which are seen to be components 

 of the resultant R. 



To construct the equilibrium polygon, take any point on the line 

 of action of P^ and draw strings o a and o b parallel to rays o a and o b, 

 b o is the equilibrant of o a and P ; through the intersection of string 

 o b and P 2 draw string c o parallel to ray c o, c o is the equilibrant of 

 o b and P 2 ; through the intersection of string c o and P 3 draw string 

 d o parallel to ray d o, d o is the equilibrant of c o and P 3 ; and through 

 the intersection of string d o and P 4 draw string e o parallel to ray e o, 

 e o is the equilibrant of d o and P 4 . Strings o a and e o acting as shown 

 are components of the resultant R, which will be parallel to R in the 

 force polygon and acts through the intersections of strings o a and e o. 



