T,S 



A corri.r. MAY n RED. 



the plain* o; B plane of the couple. M> 



the arm, and AH its new position ; the forc< u 



and act on the arm AB. At IB and A let the equal and 

 opposite forces P a /'.. /'</, each equal to P, or P s be applied, 

 acting at right angles t AB\ this will not affect the . 

 and P 8 . 



Let 2?P,, P'P 8 meet at C\ join ^L(7; ^1(7 manifestly bisects 

 tlie angle BAR. 



Now P, and P 3 are equivalent to some force in the direction 

 CA, and P l andP 4 are equivalent to an <////<// force in tin 

 tion AC. Therefore P,, P,, P 8 , P 4 are in equilibrium with 

 other; therefore the remaining forces P a , P e actii 



;>cctively produce the same effect as 2' ing at 



I respectively. Hence the proposition is true. 



We may now turn the arm of the couple through any angle 

 about B'\ and by proceeding in this way we may transfer the 

 couple to any position in its own plane. 



The effect of a couple is not altered if we transfer tic 

 couple to any plane parallel to its own, the arm rem<> 

 parallel to itself. 



Let AB be the arm, A I? its new position parallel to AB. 



A 



f 1 .. 



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