### What additional air pressure is needed to overcome

Assignment Help Civil Engineering
##### Reference no: EM13315875

A two post in ground car lift uses compressed air to force water under two aluminum pistons that move in unison (both pistons at same elevation) to raise and lower the vehicles.

The lift has a total capacity of 8,000 lbs. Each piston has a diameter of 10.5 inches.

a) Neglecting the weight of the pistons, what air pressure, in psig, is needed to raise the maximum capacity?

b) Assume that each aluminum piston is 60 inches long, and is lubricated with a 0.06 inch thick layer of water between the piston and the stationary piston encasement. Also assume the dynamic viscosity of water is 2.7X10E-5 lbf-s/ft^2. What additional air pressure, in psig, is needed to overcome the shear force that is produced when raising the vehicle at 0.1 ft/s?

c) Assume the lubricating fluid is changed to oil with a dynamic viscosity of 1.4X10E-3 lbf-s/ft^2. Now what air pressure, in psig, is required to overcome shear force ? Use the same lift rate of 0.1 ft/sec.

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