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The hydraulic oil in a car lift has a density of 8.29 x 10 2 kg/m 3 . The weight

ID: 2012950 • Letter: T

Question

The hydraulic oil in a car lift has a density of 8.29 x 102 kg/m3. The weight of the input piston is negligible. The radii of the input piston and output plunger are 5.38 x 10-3 m and 0.136 m, respectively. What input force F is needed to support the 24800-N combined weight of a car and the output plunger, when (a) the bottom surfaces of the piston and plunger are at the same level, and (b) the bottom surface of the output plunger is 1.40 m above that of the input plunger?

(a) Number 38.8 Units N

Explanation / Answer

weight Fout = 24800 N
radii of the output piston rout = 0.136 m
radii of the input piston rin = 5.38 x 10-3 m we know that , force F = pressure*area therefore , F A from this equation ,      F1/F2 = A1/A2

a) from above relation ,        Fin / Fout = Ain / Aout
                Fin = [Fout](rin / rout)2
                     = [24800 N]( 5.38 x 10-3 m / 0.136 m)2
                     = 38.80 N
b) the bottom surface of the output plunger rout = 1.4 m
               Fin / Fout = Ain / Aout
                       Fin = [Fout](rin / rout)2
                              = [24800 N]( 5.38 x 10-3 m / 1.4 m)2
                             = 0.366 N