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
The ability of falling cats to right themselves in midair and land on their feet has been a source of wonder for ages. Biologist
The ability of falling cats to right themselves in midair and land on their feet has been a source of wonder for ages. Biologist
admin
2010-04-28
54
问题
The ability of falling cats to right themselves in midair and land on their feet has been a source of wonder for ages. Biologists long regarded it as an example of adaptation by natural selection, but for physicists it bordered on the miraculous. Newton’ s laws of motion assume that the total amount of spin of a body can- not change unless an external torque speeds it up or slows it down. If a cat has no spin when it is released and experiences no external toque, it ought not to be able to twist around as it falls.
In the speed of its execution, the righting of a tumbling cat resembles a magician’ s trick. The gyrations of the cat in midair are too fast for the human eye to follow, so the process is obscured. Either the eye must be speeded up, or the cat’ s fail be slowed down for the phenomenon to be observed. A century ago the former was accomplished by means of high - speed photography using equipment now available in any pharmacy. But in the nineteenth century the capture on film of a falling cat constituted a scientific experiment.
The experiment was described in a paper presented to the Paris Academy in 1894. Two sequences of twenty photographs each, one from the side and one from behind, show a white cat in the act of righting it- .self. Grainy and quaint though they are, the photos show that the cat was dropped upside down, with no initial spin, and still landed on its feet. Careful analysis of the photos reveals the secret: As the cat rotates the front of its body clockwise, the rear and tall twist counterclockwise, so that the total spin remains zero, in perfect accord with Newton’s laws. Halfway down, the cat pulls in its legs before reversing its twist and then extends them again, with the desired end result. The explanation was that while no body can acquire spin without torque, a flexible one can readily change its orientation, or phase. Cats know this instinctively, but scientists could not be sure how it happened until they increased the speed of their perceptions a thousand fold.
How did scientists increase "the speed of their perceptions a thousand fold"?
选项
A、By analyzing photographs.
B、By observing a white cat in a dark room.
C、By dropping a cat from a greater height.
D、By studying Newton’ s Laws of motion.
答案
A
解析
最后一段中间提到:Careful analysis of the photos reveals the secret,最后提到:but scientists could not be sure how it happened until they increased the speed of their perceptions a thousand fold.前后呼应,说明科学家是通过快速摄影并分析照片的“实验”来得出结论的。故答案应为A。
转载请注明原文地址:https://kaotiyun.com/show/uMqO777K
0
专业英语八级
相关试题推荐
Walkingistheexerciseofchoiceformostdieters.Nowonder.Youdon’tneedagymmembership.Youcandoitvirtuallyeverywhe
Recentyearshavebroughtminority-ownedbusinessesintheUnitedStatesunprecedentedopportunitiesaswellasnewandsignific
A、Thefigureonthecheckexceedsthebalanceinthebankaccount,soit’sworthless.B、Ifyoucashthecheckintheamountof1
A、Becauseitisinexpensive.B、Becauseitwasrecommendedbyafriend.C、Becausetheyarecelebratingabirthday.D、Becausethey
ThecaseofJanetTraceywhodiedinAddenbrooke’shospitalafterfamilyclaimsthata"donotresuscitate"orderwasputinher
Theterm"Americandream"wasfirstusedin【B1】______inanovelwrittenbyHoratioAlger:RaggedDick.Themessagewas:Nomatte
CharlesDickensobservedofrevolutionaryFrancethatitwasthebestoftimesandtheworstoftimes,thespringofhopeandth
EmployeesintheUSarepaidfortheirtime.Thismeansthattheyaresupposedto
Mostoftheso-calledyogisintheWestseemtofocusonfigurecorrection,nottrueawareness.Theymakestatementsaboutyoga
WhichofthefollowingisNOTthefirm’srecruitmentrequirement?Wegettheimpressionfromthepassagethatinjobrecruitmen
随机试题
我国国防部的基本职能是___________。
A.本品有一定毒性,不宜持续和过量服用B.脾虚便溏者不宜服用C.大量服用能引起呃逆、眩晕、呕吐等反应D.与热茶同服可致呃逆、腹泻E.本品与乌头相反使用苦楝皮时应注意
以下说法错误的有( )。
以下对证券公司的作用说法正确的是()。Ⅰ.证券公司是证券市场投融资服务的提供者Ⅱ.证券公司是证券市场重要的机构投资者Ⅲ.证券公司为投资者提供证券及其他金融产品的投资管理服务Ⅳ.证券公司为证券发行人和投资者提供专业化的中介服务
()不以股票为媒介,适用于非股份制企业,是非股份制企业筹措权益资本的一种基本形式。
计算机指令的集合称为( )。
B
EnglishSynonymsEnglishhasthelargestvocabularyandthemostsynonymsofalllanguagesintheworld.Thisrichnessownstot
Morethanfiftyyearsago,theUnitedNationsdeclaredthatliteracyisabasichumanright.It’sveryimportantfor【B1】______th
A、Peopledeserveallthedisasters.B、Peopleshouldn’thavedeservedthedisasters.C、Peoplehavebeenreadyforthetornado.D、
最新回复
(
0
)