pressure and physics question?

In a car lift, compressed air exerts a force on a piston with a radius of 5.00 cm. This pressure is transmitted to a second piston with a radius of 15.0 cm.

a. How large a force must the compressed air exert to lift a 1.33 * 10^4 N car?

b. what pressure produces this force? Neglect the weight of pistons.

1 Answer

  • In a hydraulic lift, the pressure in equals the pressure out.

    P1 = P2

    Pressure is force over area

    P = F/A


    F2, the force out is 1.33e4 N

    F1/A1 = F2/A2

    F1 = (A1/A2)F2

    A = (pi)r^2

    (A1/A2) = 5^2 / 15^2 = 1/9

    F1 = (1/9)F2 = (1.33e4)/9 = 1.48e3 N


    P1 = F1/A1 = 1.48e8 / ((pi)(0.05^2)) = 1.88e5 N/m^2 = 1.88e5 Pa

    This pressure is approximately twice atmospheric pressure.

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