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更多“Particles move from concentrated area to less concentrated area under a thermodynamics force. The wo…”相关的问题
A、The particle of larger mass has more kinetic energy.
B、The particle of smaller mass has more kinetic energy.
C、The particles have equal kinetic energies.
D、Either particle might have more kinetic energy.
If the water is heated, the particles move more quickly, ______ with what I have said.
A．which agree
B．that agrees
C．which agrees
D．what agrees
Every geologist is familiar with the erosion cycle. No sooner has an area of land been raised alive sea-level than it becomes subject to the erosive forces of nature. The rain beats down on the ground and washed【51】the finer particles, sweeping them into rivulets and then into rivers and out to sea. The frost freezes the rain water in cracks of the rocks and breaks【52】even the hardest of the constituents of the earth's crust. Blocks of rock dislodged at high levels are brought down by the force of gravity. Alternate heating and【53】of bare rock surfaces causes their disintegration. In the dry regions of the world the wind is a powerful force in removing material from one area to another. All this is natural. But nature has also provided certain defensive forces. Bare rock surfaces are in【54】course protected by soil itself dependent initially on the weathering of the rocks. Slowly【55】surely, different types of soil with differing "profiles" evolve the main types depending primarily on the climate. The protective soil covering, once it is formed, is held together by the growth of vegetation. Grass and herbaceous plants,【56】long, branching tenuous roots, hold firmly together the surface particles. The【57】is true with the forest cover. The heaviest tropical down- pours beating on the leave of the giant trees reach the ground only【58】spray, gently watering the surface layers and penetrating along the long passages provided by the roots to the lower levels of the soil. The soil, thus protected by grass, herb, or trees, furnishes a quiet habitat for a myriad varied organisms-earth-worms that importantly modify the soil, bacteria, active in their work of converting【59】leaves and decaying vegetation into humus and food for the growing plants. Chemical action is constantly taking【60】. Soil acids attack mineral particles and salts in solution move from one layer in the soil to another.
(51)
One of the Price's findings (Paragraph 2) about the particles of the air is that ______.
A．they contain more pollutants than normal particles
B．they move much faster in high altitudes than in low altitudes
C．they are finer and lighter than normal particles
D．their ability to reflect light is much than stronger
SECTION B PASSAGES
Directions: In this section, you will hear several passages. Listen to the passages carefully and then answer the questions that follow.
听力原文： What makes it rain.9 Rain falls from clouds for the same reason anything falls to Earth. The Earth's gravity pulls it. But every cloud is made of water droplets or ice crystals. Why doesn't rain or snow fall constantly from all clouds？ The droplets or ice crystals in clouds are exceedingly small. The effect of gravity on them is minute. Air currents move and lift droplets so that the net downward displacement is zero, even though the droplets are in constant motion.
Droplets and ice crystals behave somewhat like dust in the air made visible in a shaft of sunlight. To the casual observer, dust seems to act in a totally random fashion, moving about chaotically without fixed direction. But in fact dust particles are much larger than water droplets and they finally fall. The cloud droplet of average size is only 1/2500 inch in diameter. It is so small that it would take sixteen hours to fall a mile in perfectly still air, and it does not fall out of moving air at all. Only when the droplet grows to a diameter of 1/125 inch or larger can it fall from the cloud. The average raindrop contains a million times as much water as a tiny cloud droplet. The growth of a cloud droplet to a size large enough to fall out is the cause of rain and other forms of precipitation. This important growth process is called "coalescence".
What is the main topic of the passage？
A．The mechanics of rain.
B．The climate of North America.
C．How gravity affects air current.
D．Types of clouds.
Many things in nature, such as sunshine, temperature, and precipitation, affect climate. Nearness to mountain, oceans, and large lakes affects it loo. Another factor is altitude, or height above sea level. Air cools as altitude increases. So a city at a higher altitude may be colder than one at a lower altitude. Finally, winds affect climate. They move heat and moisture between the oceans and continents. Winds keep the tropics from overheating. They keep the polar regions from getting overly cold.
Climate changes over long periods of time. Some scientists think, for example, that the earth' s climate changed at the time of the dinosaurs. They think the dinosaurs died because of the change. What causes a climate to change？ One possible cause may be changes in the sun. Sunspots, for example, are cool, dark spots that form. on the sun. Sunspots may decrease precipitation on the earth and cause unusually dry periods. Changes in the atmosphere may change climate too. Volcanic eruptions, for instance, release solid particles into the air. These particles may form. a cloud that blocks out the sun ' s heat. Human activity is another cause of climate change. Air pollution and the reduction of forest cover may have long-term effects on climate.
This passage is concerned with things that affect______.
A．precipitation
B．climate
C．altitude
D．sunspots
Droplets and ice crystals behave somewhat like dust in the air made visible in a shaft(束) of sunlight. To the casual observer, dust seems to act in a totally random fashion, moving about wildly without fixed direction. But in fact dust particles are much larger than water droplets and they finally fall. The cloud droplet of average size is only 1/2,500 inch in diameter. (78)It is so small that it would take sixteen hours to fall half a mile in perfectly still air, and it does not fall out of moving air at all. Only when the droplet grows to a diameter of 1/125 inch or larger can it fall form. the cloud. The average raindrop contains a million times as much water as a tiny cloud droplet. The growth of a cloud droplet to a size large enough to fall out is the cause of rain.
What is the main topic of the passage？
A．The mechanics of rain.
B．The climate of North America.
C．How gravity affects air current.
D．Types of clouds.
SECTION B PASSAGES
Directions: In this section, you will hear several passages. Listen to the passages carefully and then answer the questions that follow.
听力原文： What makes it rain？ Rain falls from clouds for the same reason anything falls to Earth. The Earth's gravity pulls it. But every cloud is made of water droplets or ice crystals. Why doesn't rain or snow fall constantly from all clouds？ The droplets or ice crystals in clouds are exceedingly small. The effect of gravity on them is minute. Air currents move and lift droplets so that the net downward displacement is zero, even though the droplets are in constant motion.
Droplets and ice crystals behave somewhat like dust in the air made visible in a shaft of sunlight. To the casual observer, dust seems to act in a totally random fashion, moving about chaotically without fixed direction. But in fact dust particles are much larger than water droplets and they finally fall. The cloud droplet of average size is only 1/2, 500 inch in diameter. It is so small that it would take sixteen hours to fall a mile in perfectly still air, and it does not fall out of moving air at all. Only when the droplet grows to a diameter of 1/125 inch or larger can it fall from the cloud. The average raindrop contains a million times as much water as a tiny cloud droplet. The growth of a cloud droplet to a size large enough to fall out is the cause of rain and other forms of precipitation. This important growth process is called "coalescence".
What is the main topic of the passage？
A．The mechanics of rain.
B．The climate of North America.
C．How gravity affects air current.
D．Types of clouds.
Strainers are commonly used in hydraulic systems to _____.
A.protect the pump from fine soluble contaminants
B.prevent solid particles from entering the pump
C.prevent solid particles from entering the filter
D.protect the directional control valves
The passage describes the magnetosphere as a barrier because ______.
A．it is strongest in the polar regions and the magnetic lines bunch together
B．it increases the speed of the particles from the solar wind
C．it prevents particles from the solar wind from easily entering the Earth's atmosphere
D．its position makes it difficult to be observed from the Earth
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