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
2013-04-22
79
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 ascientific 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 them 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 thousand fold.
【C7】
选项
A、Neither
B、Never
C、Either
D、Whether
答案
C
解析
本句的意思是:要观察到这一现象,要么使眼睛看事物的速度加快,要么使猫的下降速度放慢,根据either...or... 的意思,排除A、B和D。
转载请注明原文地址:https://kaotiyun.com/show/CEQK777K
0
专业英语四级
相关试题推荐
Signhasbecomeascientifichot【C1】______.【C2】______inthepast20yearshavespecialistsinlanguagestudyrealizedthatsigne
Seventy-four-year-oldsarethemost【C1】______peopleinthepopulation,accordingtoanewresearch.Fewerresponsibilities,fina
Onceuponatime,youbelievedinthetoothfairy.Youcountedonthestabilityofhousingpricesanddependedonbankerstobe,
Thursdaynight’sprogrammeonITV1,TheCostofGoingGreen,providedareasonablybalanceddebateontheimpactsofrenewablee
Decidewhichofthechoicesgivenbelowwouldbestcompletethepassageifinsertedinthecorrespondingblanks.Mostworthw
Openupmostfashionmagazinesandyouwillseeincrediblythinmodelswithimpossiblehairandwearingunreasonablyexpensive,
Pricesreachequilibriumatthelevelatwhichquantitydemanded______quantitysupplied.
Thedesegregationwasachievedthroughanumberofstruggles,_____havebeenmentionedinpreviouschapters.
随机试题
下列哪个药物属于单环β-内酰胺类抗生素()
患者,女,42岁。近2个月来右上后牙遇冷水及吃甜酸食痛,咬硬物酸软无力,无自发痛史。检查:釉质磨损,浅黄牙本质外露,硬而光滑,探针探划时有一点酸痛难忍。该患者的主诉问题是
A.面、额部B.头侧部C.肩胛部D.腹部E.胸部
某单位的汽车喷漆车间采用二氧化碳灭火系统保护。下列关于二氧化碳灭火系统灭火机理的说法中,正确的是()。
()是工艺过程最基本的组成单位。
嘉业股份公司,在上海证券交易所上市,股本总额8亿元,净资产6亿元,2014年3月5日董事会对以下几种融资方案进行讨论:(1)发行优先股方案。具体内容如下:a.公开发行优先股3亿股,筹资4亿元;b.股息率暂定为6%,以后每年根据市场情况确定股息率;c.若每
党政机关的行文关系有()。
企业内部研究开发项目开发阶段的支出,能确认为无形资产的条件有()
PASSAGETHREEWhat’stheauthor’sattitudetowardsGDPinPara.5?
A、Byfillinginsomeonlineformsaboutlocalcrashhistory.B、Byidentifyingsomeblackspotsofthelocalcommittees.C、Byrec
最新回复
(
0
)