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Question :
26. A 15 000-N car a hydraulic lift rests a : 2102188

26. A 15 000-N car on a hydraulic lift rests on a cylinder with a piston of radius 0.20 m. If a connecting cylinder with a piston of 0.040-m radius is driven by compressed air, what force must be applied to this smaller piston in order to lift the car?

A. 600 N

B. 1 500 N

C. 3 000 N

D. 15 000 N

27. By what factor is the total pressure greater at a depth of 850 m in water than at the surface where pressure is one atmosphere? (water density = 1.0 ´ 10^{3} kg/m^{3}, 1 atmosphere pressure = 1.01 ´ 10^{5} N/m^{2}, and *g* = 9.8 m/s^{2})

A. 100

B. 83

C. 74

D. 19

28. If the column of mercury in a barometer stands at 72.6 cm, what is the atmospheric pressure? (The density of mercury is 13.6 ´ 10^{3} kg/m^{3} and *g* = 9.80 m/s^{2})

A. 0.968 ´ 10^{5} N/m^{2}

B. 1.03 ´ 10^{5} N/m^{2}

C. 0.925 ´ 10^{5 }N/m^{2}

D. 1.07 ´ 10^{5} N/m^{2}

29. Dams at two different locations are needed to form a lake. When the lake is filled, the water level will be at the top of both dams. The Dam #2 is twice as high and twice as wide as Dam #1. How much greater is the force of the water on Dam #2 than the force on Dam #1? (Ignore atmospheric pressure; it is pushing on both sides of the dams.)

A. 2

B. 4

C. 8

D. 16

30. Atmospheric pressure is 1.0 ´ 10^{5} N/m^{2}, and the density of air is 1.29 kg/m^{3}. If the density of air is constant as you get higher and higher, calculate the height of the atmosphere needed to produce this pressure.

A. 7 900 m

B. 77 000 m

C. 1 260 m

D. 10 300 m