问题 填空题

住宅小区里有小石子铺的路,如图,穿着软底鞋或光着脚走在上面可以健身,它的原理是:脚底对石子压力______________(均选填“增大”、“不变”或“减小”),脚底与石子的接触面积________________,压强_____________,从而对脚底的刺激增强。

答案

不变  减小  增大

题目分析:人在路面行走时,人对地面的压力不变,当穿着软底鞋或光着脚走到有小石子铺成的路面上时,脚底对石子压力没有改变(压力等于人的自身重力),脚与路面的接触面积变小,从而压强增大,能起到按摩保健的作用

点评:(1)压强大小的影响因素:压力大小和受力面积的大小.

(2)增大压强的方法:在压力一定时,减小受力面积增大压强;在受力面积一定时,增大压力增大压强.

阅读理解

An earthquake happens when two plates rub (碰撞) together. The earth plates travel in different directions and at different speeds. If one plate is slowly forced underneath the other,  pressure builds up until the plates break apart. This process causes the ground to move. It is an earthquake. In other words, earth-quakes are the shaking of the earth’s surface caused by the earth’s rocky outer layer as a result of the energy stored within the earth. The strain within the rocks is suddenly released (释放).

The damage an earthquake causes depends on where it is and the time it is happening. If an unpopulated region is struck, there will be low loss of life or property. If it hits a large city, there may be many in-juries and much destruction. Many of the areas at risk are largely populated now. Major earthquakes hitting those areas today could produce terrible damage.

Actually, there are several million small earth-quakes every year.  Large earthquakes such as the 1964 Alaskan quake that measured 9.2 on the Richter scale, cause millions of dollars in damage. In the last 500 years, millions of people have been killed by earth-quakes around the world — including 240,000 in the 1976 Tangshan earthquake in China.

A 60-second or less earthquake can cause devastation that continues for years after the first tremor (小震). In 1972, a series of severe earthquakes struck Managua, Nicaragua. Fifteen years later, the city still looked the way it had a week after the earthquake hit, because the country did not have the necessary money to rebuild it.

The shaking of the earth is sometimes not the greatest disaster. It is in the ensuing fires and floods that often the greatest damage occurs. In the 1906 earthquake, it was the fires caused after it that did the majority of the damage. An earthquake can also destroy dams high above a city or valleys, causing floods to sweep down and sweep away everything in their path.

小题1:Which of the following is the main idea of the first paragraph?

A.An earthquake comes from inside the earth.

B.The earth has great energy in storage.

C.How the earth plates move.

D.How an earthquake happens.小题2:How many examples are used in the passage to show the damage and destruction earthquakes cause?

A.Three.

B.Four.

C.Five.

D.Six.小题3:Which of the following is mentioned to show that an earthquake can kill too many people?

A.The 1964 Alaskan quake.

B.The 1976 Tangshan earthquake.

C.The 1972 Managua earthquake.

D.The 1906 earthquake.小题4:The underlined word “ensuing” in the last paragraph probably means ______.

A.causing too much heat and great damage

B.causing many injuries and much destruction

C.happening as a result of another event

D.happening suddenly and unexpectedly小题5:By giving the example in Paragraph 4, the author wants to show that ______.

A.an earthquake doesn’t last long

B.the damage can last long

C.people in Managua suffered too much

D.Nicaragua is still a poor country

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