# Answer Key Chapter 14 - University Physics Volume 1 _ OpenStax.pdf

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8/7/2020Answer Key Chapter 14 - University Physics Volume 1 | OpenStax1/5Check Your Understanding14.1The pressure found in part (a) of the example is completely independent of the width and length of thelake; it depends only on its average depth at the dam. Thus, the force depends only on the water’s averagedepth and the dimensions of the dam, not on the horizontal extent of the reservoir. In the diagram, note thatthe thickness of the dam increases with depth to balance the increasing force due to the increasingpressure.14.2The density of mercury is 13.6 times greater than the density of water. It takes approximately 76 cm(29.9 in.) of mercury to measure the pressure of the atmosphere, whereas it would take approximately 10 m(34 ft.) of water.14.3Yes, it would still work, but since a gas is compressible, it would not operate as efficiently. When theforce is applied, the gas would first compress and warm. Hence, the air in the brake lines must be bled outin order for the brakes to work properly.Conceptual Questions1. Mercury and water are liquid at room temperature and atmospheric pressure. Air is a gas at roomtemperature and atmospheric pressure. Glass is an amorphous solid (non-crystalline) material at roomtemperature and atmospheric pressure. At one time, it was thought that glass flowed, but flowed veryslowly. This theory came from the observation that old glass planes were thicker at the bottom. It is nowthought unlikely that this theory is accurate.3. The density of air decreases with altitude. For a column of air of a constant temperature, the densitydecreases exponentially with altitude. This is a fair approximation, but since the temperature does changewith altitude, it is only an approximation.5. Pressure is force divided by area. If a knife is sharp, the force applied to the cutting surface is dividedover a smaller area than the same force applied with a dull knife. This means that the pressure would begreater for the sharper knife, increasing its ability to cut.7. If the two chunks of ice had the same volume, they would produce the same volume of water. The glacierwould cause the greatest rise in the lake, however, because part of the floating chunk of ice is alreadysubmerged in the lake, and is thus already contributing to the lake’s level.9

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