

141 





Let / which by revolving round 



./ generates a surface, Suppose a she!. 

 this surf] 



Of 



whi surface ia 



iMUiidnry, ai 

 . 



face of r- 

 



near to tho f 



Required the centre of gravity 

 of n 



off by plane* perpendicular to 

 " axis 



lie adjacent |>oint* in the exterior generating 

 pnoae /> "=*, ana 



PQ be the co-ordinates of 7'; A- the thickness of 



Contained between 



two planes jwrpendirulnr to the axis of x through P and Q 

 tcly ihryX-A*, and the abscissa of the 

 centre of graN ultimately x\ hence 







constant. 









distances from the origin of the bound - 



. 



ic centre of gravity required in on the axis of a?, we 

 need only the valu Tiler to determine its pas;' 



