THE VIRTUAL M< VMIfiHEft. 



Nxly, - Mp will be the virtual 



10 second Ixxi .<*, by t. 



moments fur the two bodies, the mutual 



holds if the bodies be in contact at more 



(3) Suppose a body in contact with a smooth fixed plane 



i>ody be displaced by 



BA C be a section of the body made by a plane through 



tint of contact A contain i common normal t 



res, and suppose this section a circle. Let l>.\ /-.' lie the 



n of tins plane 1 1 smooth plane, 



pose B'A'C' the position of the body after di#p!acemei 

 oeing the new point of contact, ai. the point in the 



bod}* M-t with the fixed smooth 



(in IHTJ 'IK- normal -1 



virtual . point of contact 



with iv- to normal force. Now An is equ 



prod lift <>f tin* chord A' a and the sine of the angle between 



le in ultimately ii. 

 nit.-ly sn; inpared with the 



also compared with tne arc A A'. 



\ve neglect powers of A A' higher than the tir>- 

 e along the normal acting a 

 point of contact is z- 



A similar result be any cures instead 



;v displac i made uj) of two, on 



second case, and one like that isc, the fixed 



;ig smooth, the virtual moment of the force exerted 

 .me will van. 



n i 



