首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
Today’s lecture is about two powerful natural forces, one destructive, yet the other productive. Tornado (龙卷风) is a typical exam
Today’s lecture is about two powerful natural forces, one destructive, yet the other productive. Tornado (龙卷风) is a typical exam
admin
2009-09-12
1.4K+
问题
Today’s lecture is about two powerful natural forces, one destructive, yet the other productive.
Tornado (龙卷风) is a typical example of destructive forces in nature. Forces other than damaging winds are also at work inside tornadoes. Sometimes as twisting, screaming wind passes over house, the walls and the ceiling burst apart as if a bomb had gone off inside. This explosion is caused by the low air pressure at the center of a tornado.
The pressure at the center of a tornado is usually 13 pounds per square inch. However, inside the house the air pressure is normal, about 15 pounds per square inch. The difference of 2 pounds per square inch between the inside and outside pressure may not seem like much. But suppose a tornado passes over a small building that measures 20 by 10 feet. On each square inch of the building, there is 2 pounds of pressure from the inside that is not balanced by air pressure outside the building. On the ceiling, that adds up to an unbalanced pressure of 57,600 pounds. The pressure on the four walls adds up to 172,800 pounds.
If windows are open in the building, some of the inside air will rush out through them. This will balance the pressure inside and outside the building. But ff the windows are shut tightly, the enormous inside pressure may cause the building to burst. Unfortunately, heavy rain and hail often occur in thunderstorms that later produce tornadoes. So people frequently shut all windows to protect their property, which may cause far worse damage later. For the same reason, tornado cellars must have an air opening. Otherwise, the cellar door might be blown out when a tornado passes over it.
Even more amazing is the strong force of plants in water evaporation (蒸发). The task of carrying 40 gallons of water up almost 60 feet -- to an apartment on the sixth floor, for instance -- is an undeniably heavy task. And yet it is no more than a full-grown tree does on any warm day. For 400 trees 75 to 90 feet high, the leaves evaporate an average of 20 tons of water on a single day -- equivalent to the capacity of a larger tanker truck. Before this water evaporates it is lifted an average of 80 feet through trunks and branches. Anyone thinks this a trifle would do well to work out how many bucks it would mean, to which floor. Quite an achievement. The surprising thing is that the plants themselves need supply no energy to do this. Everything happens automatically. The evaporation from the leaf surface causes a constant compensatory suction (吸) of water. This suction communicates itself through branch and trunk down into roots. The suction force caused by evaporation from the tiny openings of the leaves is tremendously strong. When, on a dry summer’s day, the surrounding atmosphere has a relative humidity (湿度) of 45 percent, the evaporation suction corresponds to the pull exerted on a rope 3 mm in diameter by a 154-pound man suspended from it! Thus evaporation actually draws the water from the leaves by force, and pulls more water up to replace it. The driving force is the sun and plants make direct use of its energy for water transport. Once again, we see the powerful, unlimited energy in nature.
选项
A、force of tornado increases the air pressure in a building
B、air pressure at the center of a tornado is as strong as over 172,000, pounds
C、weight of a tornado can crush a building’s roof when it passes overhead
D、air pressure inside a tornado is less than air pressure inside a building
答案
D
解析
细节推断题。本文第三段提到,由于室内正常气压与龙卷风中心低气压的差异,平均每平方英寸有两磅的向外压力不能被向内的压力抵消。参见第四段第三句:But if the windows are shut tightly,the enormous inside pressure may cause the building to burst.可推知,紧闭的窗户使室内外空气不流通,室内压力积聚,最后巨大的室内压力导致房屋爆裂。
转载请注明原文地址:https://kaotiyun.com/show/MT37777K
0
大学英语四级
相关试题推荐
ShouldMedicalSchoolBeShortenedtoThreeYears?A)ForTravisHill,itwasanoffertoogoodtorefuse.Lastyearwhenth
Springisarrivingearlierincities.Whyisthis?Arecentstudyproposedaculprit(元凶):lightpollution,akey【C1】________be
TooMuchHealthcareA)ForpeoplewhohadbeenawaitingtherolloutoftheAffordableCareActinordertoobtainhealthins
Fearresponsescanonlybeerasedwhenpeoplelearnsomethingnewwhileretrievingthefearmemory.Thisistheconclusionofa
TheAmazonMysteryA)Ifthere’sasentencethatsumsupAmazon,theweirdestmajortechnologycompanyinAmerica,it’sone
TheAmazonMysteryA)Ifthere’sasentencethatsumsupAmazon,theweirdestmajortechnologycompanyinAmerica,it’sone
A、Throughinternationaltrade.B、ThroughancientRomans’invasion.C、Throughthedevelopmentofnewtechnology.D、Throughthepo
HowtheShutdownHammeredtheU.S.EconomyA)Howmuchhavethegovernmentshutdownandthedefaultthreatcostus?Before
HowtheShutdownHammeredtheU.S.EconomyA)Howmuchhavethegovernmentshutdownandthedefaultthreatcostus?Before
Antarctica’svast,frozen,barrenlandscapehasbeckonedscholarsand【C1】________alikeformorethanacentury.Indeed,thehist
随机试题
患者,男,28岁。自幼好发扁桃体炎,8年前于劳动时出现呼吸困难,后咳粉红色泡沫痰及双下肢水肿,诊断为慢性风湿性心脏病,二尖瓣狭窄及主动脉瓣关闭不全。患者出现水冲脉,毛细血管搏动的原因是
患儿,4岁。高热8小时、呕吐4次、惊厥2次,于8月中旬入院。查体:体温40℃,血压65/40mmHg,昏睡,皮肤呈花纹状,四肢厥冷,面色苍白,腮腺不大,心肺腹检查未见异常,腱反射亢进,为明确诊断,最有意义的检查是
某房地产开发商在其新建项目的开盘仪式上,承诺对前80名购房者给予209/6的价格优惠,这种价格折扣技巧属于()。
某路基发生斜坡上的岩体或土体在自然或人为因素的影响下沿带或面滑动的地质现象,该路基属于()。
下列各账簿中,必须逐日逐笔登记的是()。
先贤苏格拉底有句名言“美德即知识”,后人对此提出质疑。请以“道德是否可教”为话题进行写作。文体不限,诗歌除外。
西周的官学已有较完备的制度,主要分两类两级:一类是国学,一类是()。
(2014年真题)下列关于宋代“翻异别推”制度的表述,正确的是()。
科学社会主义的核心内容是
TheUniversityLibraryisoneofthelargest【B1】______librariesinthecountry,witha【B2】______ofsometwomillionvolumes.T
最新回复
(
0
)