Conceptual Physics Chapter 14

25 July 2022
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question
When a party balloon is compressed to one-third its volume, gas pressure in the balloon _______. a. is also one-third b. remains the same if temperature doesn't change c. doubles d. triples
answer
d. triples according to Boyle's law, pressure is inversely proportional to volume.
question
A column of mercury 76 cm tall has a weight that is equal to _______. a. that of a column of water 10.3 meters tall b. normal atmospheric pressure c. the weight of Earth's atmosphere d. 13.6 times the density of water
answer
a. that of a column of water 10.3 meters tall If water is used in barometer, the height of the barometer tube would be at least 10.3m. Because mercury is 13.6 times more dense than water (a column weight of only 760mmHg), the tube can be much shorter.
question
A 1-kg balloon at equilibrium in the air is buoyed up with a force of _______. a. 1 kilogram b. 12 newtons c. 10 newtons d. 1 newton
answer
c. 10 newtons 1kg is equal to about 10 newtons According to archimedes principle an object surrounded by air is buoyed up by a force equal to the weight of the air displaced
question
A helium-filled balloon will reach its maximum altitude when _______. a. its weight equals the weight of displaced air b. it can no longer displace its own weight of air c. its density exceeds that of the surrounding air d. it displaces a greater weight of air than its own weight
answer
a. its weight equals the weight of displaced air Unlike the water, the atmosphere has no surface. Gas filled balloon will rise only so long as it displaces a weight of air greater than its own weight. Because air becomes less dense with altitude, the balloon eventually finds equilibrium.
question
When the speed of a fluid increases, internal pressure in the fluid _______. a. remains constant b. increases c. decreases d. increases as the square of the increase
answer
c. decreases according to Bernoulli's principle, when the speed of a fluid increases, internal pressure of the fluid decreases. This is a consequence of the conservation of energy. More speed and KE mean less pressure
question
Air pressure over the surface of a bird's wings decreases when _______. a. turning motion is executed b. the wing is tilted downward c. air speed decreases there d. air speed increases there
answer
d. air speed increases there according to Bernoulli's principle, when the speed of a fluid increases, internal pressure in the fluid decreases. in the case of the bird wing, the decreased pressure of the upper part of the wing and the increased pressure of the lower part causes lift.
question
The energy source responsible for the motion of molecules that make up the atmosphere is a. solar power. b. the pressure caused by the weight of air. c. their own natural kinetic energy. d. atmospheric tides.
answer
a. solar power.
question
A plasma differs from a gas in that a. it is electrically conducting. b. its molecules are farther apart. c. its atoms are boosted to higher atomic numbers. d. it is hotter than a gas. e. all of these
answer
a. it is electrically conducting plasma is an electrified gas
question
Atmospheric molecules do not fly off into outer space because of a. cohesive forces. b. their relatively high speeds. c. earth gravitation. d. their relatively low densities.
answer
d. earth gravitation. Atmosphere is compromise between energetic molecules that tend to fly away and the the gravity that hold them back.
question
Atmospheric pressure is caused by the a. temperature of the atmosphere. b. effect of the sun's energy on the atmosphere. c. weight of the atmosphere. d. density of the atmosphere.
answer
c. weight of the atmosphere
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A balloon is buoyed up with a force equal to the a. density of surrounding air. b. weight of the balloon and contents. c. weight of air it displaces. d. atmospheric pressure. e. all of these
answer
c. weight of air it displaces. Archimedes principle can be applied to gas just like liquid. An object surrounded by air is buoyed up by a force equal to the weight of the air it displaces
question
As a helium-filled balloon rises in the air, it becomes a. bigger. b. heavier. c. more dense. d. all of these e. none of these
answer
a. bigger When the helium balloon starts gaining height, the pressure decreases and as the gas molecules are very freely movable (higher than the normal). They move apart from each other in the meanwhile they make the balloon to expand.
question
The air in this room has a. mass. b. weight. c. energy. d. all of these e. none of these
answer
d. all of these Air is made from molecules, which means they have mass, and weight. They have KE, because they're in a gas form and are in constant motion
question
The faster a fluid moves, the a. less its internal pressure. b. greater its internal pressure. c. internal pressure is unaffected.
answer
a.less its internal pressure according to bernoulli's principle where the speed of a fluid increases, internal pressure in the fluid decreases.
question
About how high can water be theoretically lifted by a vacuum pump at sea level? a. 10.3 m b. more than 10.3 m c. less than 10.3 m
answer
a. 10.3 m
question
Gas pressure inside an inflated stretched balloon is actually a. equal to air pressure outside the balloon. b. less than air pressure outside the balloon. c. greater than air pressure outside the balloon. d. impossible to determine without knowing the type of gas.
answer
c. greater than air pressure outside the balloon.
question
A helium-filled balloon released in the atmosphere will rise until a. atmospheric pressure on the bottom of the balloon equals atmospheric pressure on the top of the balloon. b. the pressure inside the balloon equals atmospheric pressure. c. the balloon and surrounding air have equal densities. d. all of these e. none of these
answer
c. the balloon and surrounding air have equal densities. the balloon will only rise as long as it displaces a greater weight of air than it's own weight.
question
When gas in a container is squeezed to half its volume, its density a. quadruples. b. halves. c. remains the same. d. doubles.
answer
d. doubles according to Boyle's law, pressure is inversely proportional to volume.
question
A swimmer cannot use a long hose to snorkel more than a meter deep because air a. tends to liquefy in the snorkel tube. b. in the lungs cannot easily be expelled. c. at the surface will not freely enter the higher-pressure region in the compressed lungs. d. is buoyed up leaving the swimmer breathless. e. all of these
answer
c. at the surface will not freely enter the higher-pressure region in the compressed lungs.
question
In a vacuum, an object has no a. buoyant force. b. temperature. c. mass. d. weight. e. all of these
answer
a. buoyant force. In a vacuum, an object is not surrounded by anything, so it is not displacing anything such as water or air. which is needed to produce an upward buoyant force.
question
In a vacuum a marshmallow becomes a. smaller. b. larger. c. a hollow shell. d. flat. e. none of the above choices
answer
b. larger the molecules of the marshmallow are able to expand as opposed to being moved closer together by the atmospheric forces.
question
Which of the following bodies is comprised mostly of plasma? a. Sun b. Moon c. Earth d. all of these e. none of these
answer
a. Sun
question
If you release a ball inside a freely falling elevator, it stays in front of you instead of "falling to the floor" because you, the ball, the elevator, and the air in the elevator are all in free fall. If you similarly release a helium-filled balloon, the balloon will a. slowly fall. b. press against the floor. c. slowly rise. d. press against the ceiling. e. also stay in front of you.
answer
e. also stay in front of you. Like the falling ball, the balloon will also stay in front of you because it loses its buoyancy.
question
Suppose you are standing on a weighing scale and all of a sudden the atmosphere vanished. The reading on the scale would a. quickly reduce to zero. b. remain the same. c. increase. d. decrease.
answer
c. increase Because the buoyancy of the of the atmosphere disappear.
question
An umbrella tends to move upwards on a windy day principally because a. air gets trapped under the umbrella, warms, and rises. b. buoyancy increases with increasing wind speed. c. air pressure is reduced over the curved top surface. d. all of these
answer
c. air pressure is reduced over the curved top surface. The difference in air pressured above and below the umbrella causes it to lift.
question
If you made a barometer with water instead of mercury, you would have to use a tube that is 13.6 times taller. Why?
answer
Because water is not as dense as mercury, and can to expand farther
question
What pressure is exerted against bodies immersed in the atmosphere.
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Atmospheric pressure
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It results from the weight of air pressing down from above.
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Atmospheric pressure
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At sea level, atmospheric pressure is about
answer
101 kPa.
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Any device that measures atmospheric pressure.
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Barometer
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The product of pressure and volume is a constant for a given mass of confined gas, as long as temperature remains unchanged: P₁V₁ = Pβ‚‚Vβ‚‚
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Boyle's law
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An object in the air is buoyed up with a force equal to the weight of displaced air.
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Archimedes' principle (for air)
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When the speed of a fluid increases, internal pressure in the fluid decreases.
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Bernoulli's principle
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An electrified gas containing ions and free electrons.
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Plasma Most of the matter in the universe is in the plasma phase.