CENTRE OF PRESSURE 



29 



where A is the area and k its radius of gyration about the axis Y in 

 the surface, x now being the distance of the centroid of the area from the 

 surface, measured in the plane of the area. 1 



In the case of a rectangle, having its side b in the surface, and its side 

 d inclined at an angle to the vertical, 



FIG. 13. 



i.e., whatever the inclination, the C. P. is on the median line at a point 

 distant the length of the rectangle from the surface. 



Where the upper edge of the rectangle is horizontal and at a depth h 

 below the surface (Fig. 13 a) 





S = h sec & + ^ 



a 



h sec 6 + 



1 If Aj is the radius of gyration of the figure about an axis in its plane parallel to the surface 

 and passing through its C. Gr. we have A 2 = k^ + 2, so that the distance of the C. P. below 



the C. G. is X - 5 = ^ - $ = K- 



