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"Now if the plate were shaped as shown, so that the direction of the jet were completely reversed turned through 180 degrees, there would be an additional pressure on the plate, due to the reaction of the jet leaving it. This, neglecting friction, would be equal to the original impulse, thus making the total force on plate 2 F instead of F. It is quite evident that if the force is twice as great, the work must be double." —Derr, 1911

Force Measurement by Deflecting Water Jet 180 Degrees

"Now if the plate were shaped as shown, so that the direction of the jet were completely reversed turned…