sm_pdf_chapter9 - Chapter 9 Solids and Fluids Quick Quizzes...

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Chapter 9 Solids and Fluids Quick Quizzes 1. (c). The mass that you have of each element is: ( )( ) 33 3 3 19.3 10 kg/m 1 m 19.3 10 kg gold gold gold mV ρ == × = × ( )( ) 3 10.5 2 m 21.0 10 k silver silver silver × = × ( 3 g 3 2.70 6 m 16. aluminum aluminum aluminum × 3 = × 2 2. (a). At a fixed depth, the pressure in a fluid is directly proportional to the density of the fluid. Since ethyl alcohol is less dense than water, the pressure is smaller than P when the glass is filled with alcohol. 3. (c). For a fixed pressure, the height of the fluid in a barometer is inversely proportional to the density of the fluid. Of the fluids listed in the selection, ethyl alcohol is the least dense. 4. (b). The blood pressure measured at the calf would be larger than that measured at the arm. If we imagine the vascular system of the body to be a vessel containing a liquid (blood), the pressure in the liquid will increase with depth. The blood at the calf is deeper in the liquid than that at the arm and is at a higher pressure. Blood pressures are normally taken at the arm because that is approximately the same height as the heart. If blood pressures at the calf were used as a standard, adjustments would need to be made for the height of the person, and the blood pressure would be different if the person were lying down. 5. (c). The level of floating of a ship is unaffected by the atmospheric pressure. The buoyant force results from the pressure differential in the fluid. On a high-pressure day, the pressure at all points in the water is higher than on a low-pressure day. Because water is almost incompressible, however, the rate of change of pressure with depth is the same, resulting in no change in the buoyant force. 6. (b). Since both lead and iron are denser than water, both objects will be fully submerged and (since they have the same dimensions) will displace equal volumes of water. Hence, the buoyant forces acting on the two objects will be equal. 7. (a). When there is a moving air stream in the region between the balloons, the pressure in this region will be less than on the opposite sides of the balloons where the air is not moving. The pressure differential will cause the balloons to move toward each other. This is demonstration of Bernoulli’s principle in action. 331
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332 CHA P T E R 9 Answers to Even Numbered Conceptual Questions 2. We approximate the thickness of the atmosphere by using 0 PP g h ρ = + with P at the top of the atmosphere and P at sea level. This gives an approximation of 0 0 = 1 atm = () 5 4 0 10 Pa 0 1 kg m 1 h g 31 2 0 ~1 0 m s == m h or Because both the density of the air, 0 km , and the acceleration of gravity, g , decrease with altitude, the actual thickness of the atmosphere will be greater than our estimate. 4. Both must have the same strength. The force on the back of each dam is the average pressure of the water times the area of the dam. If both reservoirs are equally deep, the force is the same.
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sm_pdf_chapter9 - Chapter 9 Solids and Fluids Quick Quizzes...

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