Page 214 - Schaum's Outline of Theory and Problems of Applied Physics

CHAP. 16] FLUIDS AT REST 199

16.16. What pressure is experienced by a skin diver 20 ft below the surface of a freshwater lake?

16.17. (a) How much force is required to raise a 1000-kg block of concrete to the surface of a freshwater lake?
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(b) How much force is needed to lift it out of the water? The density of concrete is 2.3 × 10 kg/m .
16.18. An aluminum bar weighs 17 lb in air. How much force is required to support the bar when it is immersed in gasoline?
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The weight density of aluminum is 170 lb/ft and that of gasoline is 42 lb/ft .
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16.19. A raft 8 ft wide, 12 ft long, and 2 ft high is made from solid balsa wood (dg = 8 lb/ft ). How much weight can it
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support in seawater (dg = 64 lb/ft )?
16.20. People have roughly the same density as freshwater. Find the buoyant force exerted by the atmosphere on a 50-kg
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woman at sea level where the density of air is 1.3 kg/m .
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16.21. A balloon weighing 100 kg has a capacity of 1000 m . If it is filled with hydrogen, how great a payload in kilograms
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can it support? At sea level the density of hydrogen is 0.09 kg/m and that of air is 1.3 kg/m .
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16.22. A force of 50 N is applied to the input piston of a hydraulic system. The input piston has an area of 60 cm and
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the output piston has an area of 15 cm . (a) Find the force the output piston exerts. (b) Find the distance the output
piston moves when the input piston moves 2 cm.
16.23. A force of 120 N is applied to a lever with an AMA of 5 that operates the input piston of a hydraulic press. The
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input piston has an area of 10 cm and the output piston has an area of 125 cm . (a) Find the force the output piston
exerts. (b) Each stroke of the lever moves the input piston 3 cm. How many strokes are needed to move the output
piston 30 cm?
16.24. A lever with a mechanical advantage of 10 is used to apply force to the input piston of a hydraulic jack whose input
piston is 1 in. in diameter and whose output piston is 4 in. in diameter. (a) If the jack is 90 percent efficient, how
much weight can it lift when a force of 50 lb is applied to the lever? (b) If each stroke of the lever moves the input
piston 3 in., how many strokes are needed to raise the output piston 1 ft?

Answers to Multiple-Choice Questions

16.1. (b) 16.10. (d)
16.2. (c) 16.11. (c)

16.3. (c), (d) 16.12. (b)

16.4. (c) 16.13. (b)

16.5. (b) 16.14. (b)

16.6. (a) 16.15. (d)
16.7. (b) 16.16. (d)

16.8. (c) 16.17. (a)

16.9. (d)