PASCAL’S LAWPascal was a noted French physicist who discoveredthat a closed container of fluid could be used to transferforce from one place to another or to multiply forces byits transmission through a fluid. Pascal’s law may bestated as follows: PRESSURE APPLIED ANY-WHERE ON A CONFINED FLUID IS TRANS-MITTED UNDIMINISHED IN EVERY DIRECTION.THE FORCE THUS EXERTED BY THE CONFINEDFLUID ACTS AT RIGHT ANGLES TO EVERYPORTION OF THE SURFACE OF THE CONTAINERAND IS EQUAL UPON EQUAL AREAS. It should benoted that Pascal’s law applies to fluids-both gas andliquid. It is the use of Pascal’s law that makes possibletoday’s hydraulic and pneumatic systems.According to Pascal’s law, any force applied to aconfined fluid is transmitted in all directions throughoutthe fluid regardless of the shape of the container.Consider the effect of this in the systems shown in viewsA and B of figure 10-1. If there is a resistance on theoutput piston (view A, piston 2) and the input piston ispushed downward, a pressure is created through thefluid, which acts equally at right angles to surfaces in allparts of the container.If the force 1 is 100 pounds and the area of inputpiston 1 is 10 square inches, then the pressure in the fluidis 10 psi ( 100 ÷ 10). It must be emphasized that this fluidpressure cannot be created without resistance to flow,which, in this case, is provided by the 100 pound forceacting against the top of the output piston 2. Thispressure acts on piston 2 so that for each square inch ofits area it is pushed upward with a force of 10 pounds.In this case, a fluid column of uniform cross section isconsidered so that the area of the output piston 2 is thesame as the input piston 1, or 10 square inches;therefore, the upward force on the output piston 2 is 100pounds-the same as was applied to the input piston 1.All that has been accomplished in this system was totransmit the 100-pound force around a bend; however,this principle underlies practically all mechanicalapplications of fluid power.At this point, it should be noted that since Pascal’slaw is independent of the shape of the container, it is notnecessary that the tube connecting the two pistonsshould be the full area of the pistons. A connection ofany size, shape, or length will do so long as anunobstructed passage is provided. Therefore, the systemshown in view B of figure 10-1 (a relatively small, bentpipe connects two cylinders) will act exactly the sameas that shown in view A.Multiplication of ForcesIn figure 10-1, views A and B, the systems containpistons of equal area wherein the output force is equalto the input force. Consider the situation in figure 10-2where the input piston is much smaller than the outputpiston. Assume that the area of the input piston 1 is 2Figure 10-1.-Force transmitted from piston to piston.Figure 10-2.-Multiplication of force.10-2

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