. The elements of railroad engineering . pounds be applied at c(whose area is 1 squareinch), a pressure of 5 poundsper square inchwill be trans-mitted in all directions;and in order that thereshall be no movement, aforce of 6 X 5 = 30 pounds must be applied at d^ 40 poundsat e, 20 pounds at/, 100 pounds at a, and 35 pounds at b. If a force of 99 pounds were applied to a, instead of 100pounds, the piston a would rise, and the other pistonsb, c, d, e, and/ would move inwards; but, if the force appliedto a were 100 pounds, they would all be in equilibrium. Had101 pounds been applied at a, the pre
. The elements of railroad engineering . pounds be applied at c(whose area is 1 squareinch), a pressure of 5 poundsper square inchwill be trans-mitted in all directions;and in order that thereshall be no movement, aforce of 6 X 5 = 30 pounds must be applied at d^ 40 poundsat e, 20 pounds at/, 100 pounds at a, and 35 pounds at b. If a force of 99 pounds were applied to a, instead of 100pounds, the piston a would rise, and the other pistonsb, c, d, e, and/ would move inwards; but, if the force appliedto a were 100 pounds, they would all be in equilibrium. Had101 pounds been applied at a, the pressure per square inch would be -^:— = pounds, which would be transmitted20 ^ in all directions; and, since the pressure due to ^ is only 5pounds per square inch, it is now evident that the piston awill move downwards, and the pistons b, e, d, e, andywill beforced outwards. The whole may be summed up as follows: 9 7(). R u Ic.— T//e pressure per unit of area exerted any-where upon a mass of liquid is transmitted undiminished in. HYDROMECHANICS. 363 all directions, and acts with the same force tipon all S7irfacesin a direction at right angles to those siirfaccs. This law was first discovered by Pascal, and is the mostimportant in Hydromechanics. Its meaning should bethoroughly understood. Example.—If the area of the piston e in Fig. 158 were squareinches, and a force of 150 pounds were applied to it, what forces wouldhave to be applied to the other pistons to keep the water in equilibrium,assuming that their areas were the same as given before ? 150 Solution. -^-^ = lb. per sq. in., nearly. i- i J 20 X — lb. = force to balance a. 7 X = lb. = force to balance b. 1 X = lb. = force to balance c. \ Ans. 6 X = lb. = force to balance d. 4 X = lb. = force to balance /. 971. The pressure due to the weight of a liquid may bedownwards, upwards, or sideways. 972. Downward Pressure.—In Fi
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