

EMBANKMENT WHEN ONE FACE IS VERTICAL. 27 



4. Find the centre of pressure of the triangle in Ex. 2, 

 when it is inverted so that the base is in the surface of the 

 fluid. 



Ans. At a distance of \a below the surface of the fluid. 



5. An immersed rectangle has two sides horizontal, the 

 inclination of the plane of the rectangle to the horizon is 

 0, the depth of its upper side below the surface of the fluid 

 is c, the sides of the rectangle are a and 5, the latter hori- 

 zontal. Find its centre of pressure. 



[Take the upper side for the axis of y, and its middle 

 point for the origin.] 



a 3c + 2a sin 6 . _ 

 Ans. x = =- and y = 0. 

 3 Zc + a sin 6 



17. Embankments. An embankment generally con- 

 sists of a large mass of earth and other material. When 

 used for the side of a reservoir or canal, to bank up a river,* 

 to keep out the sea,f or in general to dam back water, they 

 are constructed on certain principles, and are opposed to the 

 effort made by the water to spread itself. The effort to 

 overthrow the embankment arises from the force which the 

 water exerts horizontally ; and the stability is caused by the 

 weight of the embankment. When therefore there is an 

 equilibrium, the former of these forces must be equivalent 

 to the latter. 



An embankment is generally made wider than is abso- 

 lutely necessary, to give strength and stability sufficient to 

 insure it against all risks. Frequently they slant only on 

 the side that is away from the water. In every case the 

 embankment should be built much stronger at the bottom 

 than at the top, for the pressure of water increases as the 

 depth. 



18. Embankment when the Face on the Water 

 Side is Vertical. Find the stability of an embankment 



* Called dykes. t Called eea-walle. 



