Review Questions: Gases
Answers
A. their own natural kinetic energy.
B. the pressure caused by the weight of air.
C. atmospheric tides.
D. solar power.
2. 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.
3. 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%
4. 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.
5. 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.
Reasoning: This is the same concept as
the buoyant force inside the fluids. There is a buoyant force equal to the weight
of the displaced air which acts on the balloon.
6. 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.
Reasoning:At higher elevations, there is
less pressure on the balloon. Its volume becomes larger.
7. 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.
8. 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.
9. The air in this room has
A. mass.
B. weight.
C. energy.
D. all of these.
E. none of these.
10. 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
Reasoning: The pressure of a tube of water, 10.3 meters tall, is the same as the atmospheric pressure.
11. Airplane flight best illustrates
A. Archimedes' principle.
B. Pascal's principle.
C. Bernoulli's principle.
D. Boyle's law.
Reasoning: The lifting force is produced
via Bernoulli's principle.
12. The faster a fluid moves, the
A. greater its internal pressure.
B. Less its internal pressure.
13. 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.
14. On a windy day, atmospheric pressure
A. increases.
B. decreases.
C. remains unchanged.
15. 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. neither of these.
16. Consider two mercury barometers, one with twice the cross-sectional area of the other. Neglecting capillarity, mercury in the smaller tube will rise
A. he 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.
Reasoning: Pressure depends on the height
and not on the cross sectional area of the tube.
17. 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.
18. 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.
19. As a balloon rises higher and higher into the atmosphere, its
A. volume decreases.
B. density increases.
C. weight increases.
D. mass decreases.
E. none of these.
20. 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.
21. 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.
Reasoning: As the woman goes deeper, the volume of air is her lungs are compressed more and more. Thus the density of the swimmer increases.
22. 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.
Reasoning:This is the consequence of the
Bernoulli's principle.
23. 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.
24. 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.
25. 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.