Chapter 14: Gases And Plasmas
- 1.
The energy source responsible for the motion of molecules that make up the atmosphere is
- A.
Their own natural kinetic energy.
- B.
The pressure caused by the weight of air.
- C.
Atmospheric tides.
- D.
Solar power.
Correct Answer
D. Solar power.Explanation
The correct answer is solar power. The motion of molecules in the atmosphere is primarily driven by the energy from the sun. Solar radiation heats the Earth's surface, causing the air to warm up and rise, creating convection currents. These currents then drive the movement of molecules in the atmosphere, resulting in wind and other atmospheric phenomena. The energy from the sun is therefore the main source of motion for the molecules in the atmosphere.Rate this question:
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- 2.
A plasma differs from a gas in that
- A.
A plasma differs from a gas in that
- B.
It is hotter than a gas.
- C.
It is electrically conducting.
- D.
Its atoms are boosted to higher atomic numbers.
- E.
All of these
Correct Answer
C. It is electrically conducting.Explanation
A plasma differs from a gas in that it is electrically conducting. Unlike a gas, which consists of neutral atoms or molecules, a plasma is made up of charged particles, such as ions and free electrons. These charged particles allow a plasma to conduct electricity and respond to electric and magnetic fields. This property of being electrically conducting is a fundamental characteristic that distinguishes a plasma from a gas.Rate this question:
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- 3.
Atmospheric molecules do not fly off into outer space because of
- A.
Their relatively high speeds.
- B.
Their relatively low densities.
- C.
Earth gravitation.
- D.
Cohesive forces.
Correct Answer
C. Earth gravitation.Explanation
The reason atmospheric molecules do not fly off into outer space is due to Earth's gravitation. Gravity pulls the molecules towards the Earth's surface, preventing them from escaping into outer space. The other options, such as their speeds, low densities, and cohesive forces, do not play a significant role in keeping the molecules within the atmosphere.Rate this question:
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- 4.
About what percentage of the molecules that make up the atmosphere are below an aircraft that flies at an altitude of 6 kilometers?
- A.
20%
- B.
30%
- C.
40%
- D.
50%
- E.
More than 50%
Correct Answer
E. More than 50%Explanation
At an altitude of 6 kilometers, the majority of the Earth's atmosphere is below the aircraft. Since the atmosphere gradually becomes less dense as altitude increases, it can be inferred that more than 50% of the molecules that make up the atmosphere are below the aircraft at this height.Rate this question:
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- 5.
Atmospheric pressure is caused by the
- A.
Density of the atmosphere.
- B.
Weight of the atmosphere.
- C.
Temperature of the atmosphere.
- D.
Effect of the sun's energy on the atmosphere.
Correct Answer
B. Weight of the atmospHere.Explanation
Atmospheric pressure is caused by the weight of the atmosphere. The air molecules in the atmosphere have mass and are pulled towards the Earth's surface due to gravity. As a result, the weight of the atmosphere exerts pressure on the Earth's surface and all objects within it. This pressure decreases with increasing altitude since there is less atmosphere above. Therefore, the weight of the atmosphere is responsible for the atmospheric pressure experienced at any given location.Rate this question:
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- 6.
What is the approximate mass of a 1-square-centimeter column of air that extends from sea level to the top of the atmosphere?
- A.
1 gram
- B.
1 kilogram
- C.
10 kilograms
- D.
100 kilograms
Correct Answer
B. 1 kilogramExplanation
The approximate mass of a 1-square-centimeter column of air that extends from sea level to the top of the atmosphere is 1 kilogram. This is because air has a density of about 1.2 kilograms per cubic meter, and a 1-square-centimeter column of air would have a height of approximately 10,000 meters (the height of the atmosphere). Therefore, the mass of the column can be calculated by multiplying the density by the volume, which is 1.2 kilograms per cubic meter multiplied by 0.0001 cubic meters, resulting in 0.00012 kilograms or 1 kilogram when rounded to the nearest gram.Rate this question:
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- 7.
The weight of a 1-square-meter column of air that extends from sea level to the top of the atmosphere is
- A.
101 N.
- B.
10,100 N.
- C.
101,000 N.
- D.
101,000,000 N.
Correct Answer
C. 101,000 N.Explanation
The weight of a column of air is determined by its density and height. As we move higher in the atmosphere, the density of air decreases. However, the height of the column also increases. In this question, the weight of the column is given as 101,000 N, which is the correct answer. This suggests that the density of air decreases enough with height to compensate for the increase in height, resulting in a constant weight for the column of air from sea level to the top of the atmosphere.Rate this question:
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- 8.
A balloon is buoyed up with a force equal to the
- A.
Weight of air it displaces.
- B.
Density of surrounding air.
- C.
Atmospheric pressure.
- D.
Weight of the balloon and contents.
- E.
All of these
Correct Answer
A. Weight of air it displaces.Explanation
The correct answer is "weight of air it displaces." When a balloon is filled with air or gas, it displaces an amount of air equal to its volume. According to Archimedes' principle, an object immersed in a fluid experiences an upward buoyant force equal to the weight of the fluid it displaces. In this case, the balloon experiences a buoyant force equal to the weight of the air it displaces, which allows it to float in the surrounding air. The other options, such as density of surrounding air, atmospheric pressure, and weight of the balloon and contents, are not accurate explanations for why a balloon is buoyed up.Rate this question:
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- 9.
As a helium-filled balloon rises in the air, it becomes
- A.
Bigger.
- B.
More dense.
- C.
Heavier.
- D.
All of these
- E.
None of these
Correct Answer
A. Bigger.Explanation
As a helium-filled balloon rises in the air, it becomes bigger. This is because the atmospheric pressure decreases as we go higher in the atmosphere. The helium inside the balloon expands in response to the decrease in pressure, causing the balloon to increase in size.Rate this question:
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- 10.
A bubble of air released from the bottom of a lake
- A.
Rises to the top at constant volume.
- B.
Becomes smaller as it rises.
- C.
Becomes larger as it rises.
- D.
Alternately expands and contracts as it rises.
- E.
None of these
Correct Answer
C. Becomes larger as it rises.Explanation
As the bubble of air rises from the bottom of the lake, the pressure surrounding the bubble decreases. According to Boyle's law, the volume of a gas is inversely proportional to its pressure. Therefore, as the pressure decreases, the volume of the bubble increases, causing it to become larger as it rises.Rate this question:
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- 11.
A one-ton blimp hovers in the air. The buoyant force acting on it is
- A.
Zero.
- B.
One ton.
- C.
Less than one ton.
- D.
More than one ton.
Correct Answer
B. One ton.Explanation
The buoyant force acting on the one-ton blimp is equal to its weight, which is one ton. According to Archimedes' principle, the buoyant force exerted on an object immersed in a fluid is equal to the weight of the fluid displaced by the object. Since the blimp is hovering in the air, it displaces an amount of air equal to its own weight, resulting in a buoyant force of one ton.Rate this question:
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- 12.
A common 5-liter metal can will float in air if it is
- A.
Evacuated of air.
- B.
Filled with a very large amount of helium.
- C.
Thrown high enough.
- D.
A can will not float in air unless the displaced air weighs more than the can and its contents.
Correct Answer
D. A can will not float in air unless the displaced air weighs more than the can and its contents.Explanation
The given answer explains that a can will not float in air unless the displaced air weighs more than the can and its contents. This is because the principle of buoyancy states that an object will float in a fluid if the weight of the fluid displaced by the object is greater than the weight of the object itself. In this case, the can will only float if the weight of the air it displaces is greater than the weight of the can and its contents combined.Rate this question:
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- 13.
In drinking soda or water through a straw, we make use of
- A.
Capillary action.
- B.
Surface tension.
- C.
Atmospheric pressure.
- D.
Bernoulli's principle.
- E.
None of these
Correct Answer
C. AtmospHeric pressure.Explanation
When we drink soda or water through a straw, we make use of atmospheric pressure. When we suck on the straw, we create a lower pressure inside the straw than the atmospheric pressure outside. This pressure difference causes the liquid to rise up the straw and into our mouths. Capillary action refers to the ability of a liquid to flow against gravity in a narrow tube, which is not applicable in this scenario. Surface tension is the force that causes the surface of a liquid to behave like a stretched elastic sheet, but it is not directly involved in drinking through a straw. Bernoulli's principle relates to the relationship between the speed and pressure of a fluid, but it is not relevant in this context.Rate this question:
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- 14.
The air in this room has
- A.
Mass.
- B.
Weight.
- C.
Energy.
- D.
All of these
- E.
None of these
Correct Answer
D. All of theseExplanation
The air in a room possesses mass because it is made up of molecules that have mass. It also has weight because weight is the force exerted by gravity on an object, and air is affected by gravity. Additionally, air molecules possess kinetic energy due to their constant motion, so the air in the room also has energy. Therefore, the correct answer is "all of these."Rate this question:
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- 15.
About how high can water be theoretically lifted by a vacuum pump at sea level?
- A.
Less than 10.3 m
- B.
More than 10.3 m
- C.
10.3 m
Correct Answer
C. 10.3 mExplanation
A vacuum pump works by creating a partial vacuum, which decreases the pressure in a closed system. At sea level, the maximum height that water can be lifted by a vacuum pump is 10.3 meters. This is because the atmospheric pressure at sea level can support a column of water approximately 10.3 meters high. If the water column is higher than this, the atmospheric pressure will not be sufficient to lift it, and the water will not be able to be lifted any higher.Rate this question:
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- 16.
The flight of a blimp best illustrates
- A.
The principle of Archimedes.
- B.
Pascal's principle.
- C.
Bernoulli's principle.
- D.
Boyle's law.
Correct Answer
A. The principle of Archimedes.Explanation
The flight of a blimp best illustrates the principle of Archimedes because blimps rely on the principle of buoyancy, which is a direct application of Archimedes' principle. According to Archimedes' principle, an object immersed in a fluid experiences an upward buoyant force equal to the weight of the fluid displaced by the object. In the case of a blimp, the gas inside the blimp is less dense than the surrounding air, causing the blimp to float in the air. This principle allows blimps to stay afloat and be able to navigate through the atmosphere.Rate this question:
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- 17.
Airplane flight best illustrates
- A.
Archimedes' principle.
- B.
Pascal's principle.
- C.
Bernoulli's principle.
- D.
Boyle's law.
Correct Answer
C. Bernoulli's principle.Explanation
Airplane flight best illustrates Bernoulli's principle. According to Bernoulli's principle, as the speed of a fluid (or air) increases, its pressure decreases. In the case of an airplane, the curved shape of the wings causes the air to move faster over the top surface compared to the bottom surface. This creates a pressure difference, with lower pressure on top and higher pressure on the bottom, resulting in lift. This lift force allows the airplane to overcome gravity and stay in the air. Therefore, airplane flight is a prime example of Bernoulli's principle in action.Rate this question:
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- 18.
The faster a fluid moves, the
- A.
Greater its internal pressure.
- B.
Less its internal pressure.
- C.
Internal pressure is unaffected.
Correct Answer
B. Less its internal pressure.Explanation
This is because as a fluid moves faster, its kinetic energy increases. According to Bernoulli's principle, an increase in kinetic energy results in a decrease in pressure. Therefore, the faster a fluid moves, the less its internal pressure.Rate this question:
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- 19.
When water is turned on in a shower, the shower curtain moves towards the water. This has to do with
- A.
Capillary action.
- B.
Surface tension.
- C.
Heat capacity.
- D.
Pressure of a moving fluid.
- E.
None of these
Correct Answer
D. Pressure of a moving fluid.Explanation
When water is turned on in a shower, the shower curtain moves towards the water because of the pressure of the moving fluid. As water flows out of the showerhead, it creates a high-pressure zone that pushes against the curtain, causing it to move. This phenomenon is similar to how wind can push objects in its path. Capillary action, surface tension, and heat capacity do not directly explain the movement of the shower curtain in this scenario.Rate this question:
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- 20.
If a strong wind from the west breaks a window in the north wall of a house, most of the glass will fall
- A.
Upward.
- B.
Inside the house.
- C.
Outside the house.
Correct Answer
C. Outside the house.Explanation
When a strong wind from the west breaks a window in the north wall of a house, the majority of the glass will fall outside the house. This is because the force of the wind will push the shattered glass fragments away from the house, causing them to fall in the direction of the wind. Additionally, the force of gravity will also contribute to the glass falling outside rather than inside the house.Rate this question:
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- 21.
A suction cup sticks to a wall. It is
- A.
Pulled to the wall by the vacuum.
- B.
Pushed to the wall by the atmosphere.
- C.
Both of these
- D.
Both of these
Correct Answer
B. Pushed to the wall by the atmospHere.Explanation
The suction cup sticks to the wall because it is pushed to the wall by the atmosphere. The atmosphere exerts pressure on the surface of the suction cup, creating a force that pushes it against the wall. This atmospheric pressure is greater than the pressure inside the suction cup, causing it to stick to the wall.Rate this question:
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- 22.
A column that extends from sea level to the top of the atmosphere contains a certain mass of air. If the same column instead had the same mass of mercury in it, the height of the mercury column would be
- A.
1/13.6 times the height of the atmosphere.
- B.
About 3/4 meter.
- C.
10.3 meters.
- D.
About 5.6 kilometers.
Correct Answer
B. About 3/4 meter.Explanation
If a column of air extends from sea level to the top of the atmosphere, and it contains a certain mass of air, then if the same column had the same mass of mercury instead, the height of the mercury column would be about 3/4 meter. This is because mercury is much denser than air, so a smaller height is needed to contain the same mass.Rate this question:
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- 23.
A column that extends from sea level to the top of the atmosphere contains a certain mass of air. If the same column instead had the same mass of water in it, the height of the water column would be
- A.
1/13.6 times the height of the atmosphere.
- B.
About 3/4 meter.
- C.
10.3 meters.
- D.
About 5.6 kilometers.
Correct Answer
C. 10.3 meters.Explanation
The density of water is about 13.6 times greater than the density of air. Since the mass of the column remains the same, if the same mass of water is used instead of air, the height of the water column would be 1/13.6 times the height of the air column. Therefore, the height of the water column would be approximately 10.3 meters.Rate this question:
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- 24.
Consider two mercury barometers, one with twice the cross-sectional area of the other. Neglecting capillarity, mercury in the smaller tube will rise
- A.
The same height as in the larger tube.
- B.
Twice as high as mercury in the larger tube.
- C.
Four times as high as mercury in the larger tube.
- D.
More than four times as high as in the larger tube.
- E.
None of these
Correct Answer
A. The same height as in the larger tube.Explanation
The height of mercury in a barometer is determined by the atmospheric pressure pushing down on the mercury in the dish. The pressure is the same regardless of the cross-sectional area of the tube. Therefore, the height of the mercury in the smaller tube will be the same as in the larger tube.Rate this question:
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- 25.
Gas pressure inside an inflated stretched balloon is actually
- A.
Less than air pressure outside the balloon.
- B.
Equal to air pressure outside the balloon.
- C.
Greater than air pressure outside the balloon.
- D.
Impossible to determine without knowing the type of gas.
Correct Answer
C. Greater than air pressure outside the balloon.Explanation
The gas pressure inside an inflated stretched balloon is greater than the air pressure outside the balloon. This is because when the balloon is inflated, the gas molecules inside the balloon collide with the inner surface of the balloon, creating a force that pushes outward. This force, combined with the elasticity of the balloon, causes the gas pressure inside to be greater than the air pressure outside.Rate this question:
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- 26.
As a high-altitude balloon sinks lower and lower into the atmosphere, it undergoes a decrease in
- A.
Volume.
- B.
Density.
- C.
Weight.
- D.
Mass.
- E.
None of these
Correct Answer
A. Volume.Explanation
As a high-altitude balloon sinks lower into the atmosphere, the air pressure surrounding the balloon increases. This increased pressure compresses the gas inside the balloon, causing its volume to decrease. The density, weight, and mass of the balloon remain the same, as these properties are determined by the amount of gas and material present in the balloon, which does not change as it descends. Therefore, the correct answer is volume.Rate this question:
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- 27.
As a balloon rises higher and higher into the atmosphere, its
- A.
Volume decreases.
- B.
Density increases.
- C.
Weight increases.
- D.
Mass decreases.
Explanation
As a balloon rises higher and higher into the atmosphere, its volume decreases. This is because as the balloon ascends, the air pressure surrounding it decreases. The decrease in air pressure causes the gas inside the balloon to expand, which leads to an increase in volume. Conversely, as the balloon descends, the air pressure increases, causing the gas inside the balloon to compress and the volume to decrease. Therefore, the correct answer is that the volume of the balloon decreases as it rises higher into the atmosphere.Rate this question:
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- 28.
A helium-filled balloon released in the atmosphere will rise until
- A.
The pressure inside the balloon equals atmospheric pressure.
- B.
Atmospheric pressure on the bottom of the balloon equals atmospheric pressure on the top of the balloon.
- C.
The balloon and surrounding air have equal densities.
- D.
All of these
- E.
None of these
Correct Answer
C. The balloon and surrounding air have equal densities.Explanation
When a helium-filled balloon is released in the atmosphere, it will rise until the balloon and the surrounding air have equal densities. This is because helium is lighter than the surrounding air, so it creates buoyancy that causes the balloon to float upwards. As the balloon rises, it will continue to ascend until it reaches a point where the density of the helium inside the balloon matches the density of the surrounding air. At this point, the buoyant force acting on the balloon will be equal to the gravitational force pulling it downwards, resulting in a state of equilibrium and causing the balloon to stop rising. Therefore, the correct answer is that the balloon and surrounding air have equal densities.Rate this question:
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- 29.
Two vertical tubes of equal cross-sectional areas are filled with water and mercury. If water is filled to a depth of 10.3 m and mercury to a depth of 0.76 m, both liquids have equal
- A.
Volumes.
- B.
Densities.
- C.
Weights.
- D.
Viscosity.
- E.
None of these
Correct Answer
C. Weights.Explanation
The weight of a liquid is directly proportional to its depth and density. In this case, the water and mercury are filled to different depths, but since the cross-sectional areas of the tubes are equal, the weight of the water will be equal to the weight of the mercury. Therefore, the correct answer is weights.Rate this question:
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- 30.
Alcohol is less dense than water. If alcohol is used to make a barometer on a day when atmospheric pressure is normal, the height of the alcohol column would be
- A.
Less than 10.3 m.
- B.
More than 10.3 m.
- C.
10.3 m.
Correct Answer
B. More than 10.3 m.Explanation
Alcohol is less dense than water, so if it is used to make a barometer, the height of the alcohol column would be more than 10.3 m. This is because the height of the column in a barometer is directly proportional to the density of the liquid used. Since alcohol is less dense than water, the column would need to be taller to balance the atmospheric pressure.Rate this question:
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- 31.
Compared to the buoyant force of the atmosphere on a 1-liter helium-filled balloon, the buoyant force of the atmosphere on a nearby 1-liter solid iron block is
- A.
Considerably less.
- B.
Considerably more.
- C.
The same.
Correct Answer
C. The same.Explanation
The buoyant force on an object is determined by the weight of the fluid it displaces. Both the helium-filled balloon and the solid iron block displace the same volume of air, which means they experience the same buoyant force from the atmosphere. The buoyant force is not affected by the material or density of the object, only by the volume of fluid it displaces. Therefore, the buoyant force on the helium-filled balloon and the solid iron block is the same.Rate this question:
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- 32.
Compared to the buoyant force of the atmosphere on a 1-kilogram helium-filled balloon, the buoyant force of the atmosphere on a nearby 1-kilogram solid iron block is
- A.
Considerably less.
- B.
Considerably more.
- C.
The same.
Correct Answer
A. Considerably less.Explanation
The buoyant force on an object is equal to the weight of the fluid it displaces. Since the helium-filled balloon is less dense than the atmosphere, it displaces a larger volume of air and experiences a greater buoyant force. On the other hand, the solid iron block is denser than the atmosphere and displaces a smaller volume of air, resulting in a smaller buoyant force. Therefore, the buoyant force on the helium-filled balloon is considerably less than the buoyant force on the solid iron block.Rate this question:
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- 33.
As a woman holding her breath swims deeper and deeper beneath the water's surface, her density
- A.
Increases.
- B.
Decreases.
- C.
Remains the same.
Correct Answer
A. Increases.Explanation
As a woman holds her breath and swims deeper beneath the water's surface, the pressure increases. This increased pressure compresses the air in her lungs, reducing its volume and increasing her density. As density is mass divided by volume, and mass remains constant, the decrease in volume causes an increase in density. Therefore, her density increases as she swims deeper.Rate this question:
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- 34.
When gas in a container is squeezed to half its volume, its density
- A.
Halves.
- B.
Doubles.
- C.
Quadruples.
- D.
Remains the same.
Correct Answer
B. Doubles.Explanation
When gas in a container is squeezed to half its volume, the same amount of gas particles are now occupying a smaller space. This means that the gas particles are now closer together, resulting in an increase in density. Therefore, the density of the gas doubles when it is squeezed to half its volume.Rate this question:
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- 35.
When gas in a container is squeezed to half its volume and the temperature remains the same, the gas pressure
- A.
Halves.
- B.
Doubles.
- C.
Quadruples.
- D.
Remains the same.
Correct Answer
B. Doubles.Explanation
When gas in a container is squeezed to half its volume and the temperature remains the same, the gas pressure doubles. This is because according to Boyle's Law, the pressure of a gas is inversely proportional to its volume when the temperature is constant. Therefore, when the volume is halved, the pressure must double to maintain the same temperature.Rate this question:
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- 36.
The depth to which an inverted drinking glass must be pushed beneath the surface of water so that the volume of enclosed air is squeezed to half is
- A.
76 cm.
- B.
10.3 m.
- C.
14.7 m.
- D.
20.6 m.
- E.
29.4 m.
Correct Answer
B. 10.3 m. -
- 37.
A swimmer cannot use a long hose to snorkel more than a meter deep because air
- A.
In the lungs cannot easily be expelled.
- B.
Tends to liquify in the snorkel tube.
- C.
Is buoyed up leaving the swimmer breathless.
- D.
At the surface will not freely enter the higher-pressure region in the compressed lungs.
- E.
All of these
Correct Answer
D. At the surface will not freely enter the higher-pressure region in the compressed lungs.Explanation
When a swimmer uses a long hose to snorkel more than a meter deep, the air at the surface will not freely enter the higher-pressure region in the compressed lungs. This is because the pressure increases as the swimmer goes deeper, making it difficult for the air to enter the lungs against the higher pressure. As a result, the swimmer will not be able to breathe properly and may feel breathless.Rate this question:
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- 38.
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
Correct Answer
C. Air pressure is reduced over the curved top surface.Explanation
On a windy day, an umbrella tends to move upwards because air pressure is reduced over the curved top surface. As the wind blows, it creates a pressure difference between the upper and lower surfaces of the umbrella. The curved shape of the umbrella causes the air to move faster over the top surface, creating a lower pressure compared to the bottom surface. This pressure difference results in a net upward force on the umbrella, causing it to move upwards. The other options do not fully explain this phenomenon.Rate this question:
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- 39.
Wind blowing over the top of a hill
- A.
Increases atmospheric pressure there.
- B.
Decreases atmospheric pressure there.
- C.
Does not affect atmospheric pressure there.
Correct Answer
B. Decreases atmospHeric pressure there.Explanation
When wind blows over the top of a hill, it creates a phenomenon known as Bernoulli's principle. According to this principle, as the wind moves faster over the hill, the air pressure decreases. This is because the faster-moving air creates a lower pressure zone. As a result, the atmospheric pressure over the top of the hill decreases. Therefore, the correct answer is that wind blowing over the top of a hill decreases atmospheric pressure there.Rate this question:
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- 40.
The Bernoulli effect causes passing ships to be drawn together when the ships are close and moving in
- A.
The same direction.
- B.
Opposite directions.
- C.
Either the same or opposite directions.
Correct Answer
C. Either the same or opposite directions.Explanation
The Bernoulli effect is the phenomenon where an increase in the speed of a fluid (in this case, water) results in a decrease in pressure. When two ships are close to each other and moving in the same direction, the faster-moving ship creates an area of low pressure between the ships, causing them to be drawn together. Similarly, when the ships are moving in opposite directions, the difference in pressure on either side of the ships causes them to be drawn towards each other. Therefore, the Bernoulli effect can cause passing ships to be drawn together either when they are moving in the same direction or in opposite directions.Rate this question:
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- 41.
It would be easier to pull evacuated Magdeburg hemispheres apart when they are
- A.
Held upside down.
- B.
At sea level.
- C.
20 km beneath the ocean surface.
- D.
20 km above the ocean surface.
- E.
None of these
Correct Answer
D. 20 km above the ocean surface.Explanation
When the evacuated Magdeburg hemispheres are held upside down, the pressure inside the hemispheres is equal to the atmospheric pressure, making it difficult to pull them apart. However, when they are 20 km above the ocean surface, the atmospheric pressure decreases significantly, reducing the pressure inside the hemispheres. This lower pressure inside the hemispheres makes it easier to pull them apart.Rate this question:
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- 42.
In a vacuum, an object has no
- A.
Buoyant force.
- B.
Mass.
- C.
Weight.
- D.
Temperature.
- E.
All of these
Correct Answer
A. Buoyant force.Explanation
In a vacuum, there is no medium or fluid to exert a buoyant force on an object. Buoyant force is the upward force exerted by a fluid on a submerged or immersed object, which counteracts the weight of the object. In the absence of a fluid, there is no buoyant force acting on the object. Therefore, the correct answer is buoyant force.Rate this question:
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- 43.
Estimate the mass of air inside an average automobile.
- A.
2 grams
- B.
2 kilograms
- C.
20 kilograms
- D.
200 kilograms
- E.
2000 kilograms
Correct Answer
B. 2 kilogramsExplanation
The correct answer is 2 kilograms because an average automobile contains a significant amount of air in its tires, engine, and other parts. While the exact mass may vary depending on the size and type of vehicle, 2 kilograms is a reasonable estimate for the mass of air inside an average automobile.Rate this question:
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- 44.
Suspend a pair of Ping-Pong balls from two strings so there is a small space between them. If you blow air between the balls, they will swing
- A.
Toward each other.
- B.
Apart from each other.
- C.
Away from the air stream, but not necessarily toward or apart from each other.
Correct Answer
A. Toward each other.Explanation
When air is blown between the Ping-Pong balls, it creates a region of low pressure. This low pressure area causes the balls to move towards each other. This is because the higher pressure outside the low pressure region pushes the balls towards the area of lower pressure, causing them to swing towards each other.Rate this question:
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- 45.
Suppose you are standing on a weighing scale and all of a sudden the atmosphere vanished. The reading on the scale would
- A.
Increase.
- B.
Decrease.
- C.
Remain the same.
- D.
Quickly reduce to zero.
Correct Answer
A. Increase.Explanation
When the atmosphere vanishes, the air pressure surrounding the weighing scale decreases significantly. As a result, the upward force exerted by the air on the scale decreases, while the downward force exerted by the person standing on the scale remains the same. This causes an imbalance in forces, resulting in an increase in the reading on the scale. Therefore, the correct answer is increase.Rate this question:
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- 46.
Assuming no change in temperature, as a freely expanding helium-filled balloon rises in the atmosphere, the buoyant force that acts on it
- A.
Increases.
- B.
Decreases.
- C.
Remains nearly the same for a long way.
Correct Answer
C. Remains nearly the same for a long way.Explanation
As a helium-filled balloon rises in the atmosphere, the buoyant force acting on it remains nearly the same for a long way. This is because the buoyant force is determined by the difference in density between the helium inside the balloon and the surrounding air. As the balloon rises, the density of the air decreases, but the density of the helium remains constant. Therefore, the difference in density and thus the buoyant force remain nearly constant.Rate this question:
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- 47.
The weight of air in a bathtub (about 1/3 cubic meter) is about the same as the weight of
- A.
A pea.
- B.
An egg.
- C.
A small apple.
- D.
A pound of butter.
- E.
A 10-pound sack of potatoes.
Correct Answer
D. A pound of butter.Explanation
The weight of air in a bathtub is very light, similar to the weight of a pound of butter. The other options, such as a pea, an egg, a small apple, and a 10-pound sack of potatoes, are either too light or too heavy to be comparable to the weight of air in a bathtub.Rate this question:
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- 48.
A large block of wood and a smaller block of iron on weighing scales both register the same weight – 1 ton. Taking buoyancy of air into account, which has the greater mass?
- A.
Wood
- B.
Iron
- C.
Both have the same mass.
- D.
More information is needed.
Correct Answer
A. WoodExplanation
The large block of wood has a greater mass than the smaller block of iron. The buoyancy of air affects the weight measurement on the weighing scales, but it does not change the mass of the objects. Therefore, despite registering the same weight on the scales, the wood block has a greater mass than the iron block.Rate this question:
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- 49.
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.
Also stay in front of you.
- B.
Press against the ceiling.
- C.
Press against the floor.
- D.
Slowly rise.
- E.
Slowly fall.
Correct Answer
A. Also stay in front of you.Explanation
When a ball is released inside a freely falling elevator, it stays in front of you because all the objects inside the elevator, including you, the ball, and the air, are in free fall together. This means that they are all experiencing the same acceleration due to gravity and are falling at the same rate. Similarly, when a helium-filled balloon is released, it will also stay in front of you because it is buoyant in air. The buoyant force acting on the balloon is greater than the force of gravity pulling it down, causing it to rise slowly. Therefore, the correct answer is that the balloon will also stay in front of you.Rate this question:
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- 50.
A car with closed windows makes a left hand turn. A helium-filled balloon in the car will
- A.
Move to the right.
- B.
Move to the left.
- C.
Move to the front.
- D.
Move to the back.
- E.
Not move.
Correct Answer
B. Move to the left.Explanation
When a car makes a left-hand turn, there is a centrifugal force acting towards the right, pushing objects in the car towards the left. Since the helium-filled balloon is lighter than air, it will be affected by this force and move towards the left side of the car. Therefore, the balloon will move to the left.Rate this question:
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Mar 19, 2023Quiz Edited by
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