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
2010-02-17
76
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 【C1】______ by natural selection, but for physicists it bordered on the miraculous. Newton’s laws of motion 【C2】______ that the total amount of spin of a body cannot change 【C3】______ an external torque speeds it up or slows it down. If a cat has no spin when it is released and experiences no external torque, it ought not to be able to 【C4】______ as it falls.
In the speed of its execution, the 【C5】______ of a tumbling cat resembles a magician’s trick. The gyrations of the cat in midair are 【C6】______ fast for the human eye to follow, so the process is obscured.【C7】______ the eye must be speeded up, or the cat’s fall slowed down for the phenomenon to be observed. A century ago the former was accomplished 【C8】______ high-speed photography using equipment now 【C9】______ in any pharmacy. But in the nineteenth century the 【C10】______ 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【C11】______ one from the side and one from behind, 【C12】______ a white cat in the act of righting itself. Grainy and quaint 【C13】______ 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 【C14】______ , the rear and tail twist counterclockwise, 【C15】______ the total spin remains zero, 【C16】______ Newton’s laws. Halfway down, the cat pulls in its legs before reversing its twist and then extends them again, 【C17】______ the desired end result. The explanation was that while no body can acquire spin without torque, a flexible one can readily change its 【C18】______ . Cats know this instinctively, but scientists could not be sure how it happened 【C19】______ they increased the speed of their 【C20】______ a thousandfold.
【C14】
选项
A、counterclockwise
B、upside down
C、clockwise
D、anticlockwise
答案
C
解析
转载请注明原文地址:https://kaotiyun.com/show/iOnK777K
0
专业英语四级
相关试题推荐
Theroleofteachersineducationextendspastresponsibilityofpassingalonginformation.Asthenamesuggests,theprimaryf
Thesedays,sciencemayhavedissectedalmosteveryelementofourdiet,butmanyofusstillfeelatthesea.Evenwhensticki
Thelandofapplepieandbaseball—theUnitedStatesofAmerica.OfcourseweallknowthereismoretoAmericathanapplepie
Itisreportedthatthirtypeoplewerekilledina______ontherailwayyesterday.
Generallyspeaking,theyhadawonderfulholidayattheseaside,butthelastthreedayswere___________bytheunexpectedstor
Inatelephonesurveyofmorethan2,000adults,21%saidtheybelievedthesunrevolved(旋转)aroundtheearth.An【C1】______7%d
Generallyspeaking,aBritishiswidelyregardedasaquiet,shyandconservativepersonwhois【C1】______onlyamongthosewith
PleaseRecycleThatBobsledRun(大学橇滑道) Forthe1992WinterGames,Frenchorganizersconstructedanewmotorway,pa
Lichenscanbespectacularforanyonewhocarestolook,butfewpeopletakethetrouble.Oftenmodestlycolored,andseemingly
SomecallittheSmartShooter,anewrifleforAmericaninfantrytroopsthatistwoweaponsinone,isaccurateupto1,000yar
随机试题
Thesheetsaredampwithsweat.You’recold,butyourheartisracingasifakillerjustchasedyoudownadarkstreet.Itwas
如何理解科教兴国战略和人才强国战略?
患者,女性,52岁。1个月前出现进食后腹胀,伴腰酸、乏力、无发热、反酸、嗳气,无腹痛,自发病以来体重下降7kg。查体:腹部可及直径约15cm质硬肿物,边界不清,活动度差,无压痛。术后病理证实为腹膜后脂肪肉瘤,其来源为
下列哪项不是阳陵泉的主治病证
“利小便即所以实大便”的理论依据是()
肺结核的活动程度是如何进行分期的?
环境影响评价的工作要求是()。
人造地球卫星所受的向心力与轨道半径r的关系,下列说法中正确的是()
美国心理学家格塞尔认为对人的发展起决定作用的因素是_______。
Youaregoingtoreadanextractfromanovel.Forquestions7-13,choosetheanswer(A,B,CorD)whichyouthinkfitsbestac
最新回复
(
0
)