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
39
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.
【C9】
选项
A、believable
B、useable
C、practical
D、available
答案
D
解析
转载请注明原文地址:https://kaotiyun.com/show/dOnK777K
0
专业英语四级
相关试题推荐
ThehistoryofindigenouseducationprovisionthroughoutAustralia’sremoteareasisrepletewithinstancesofneglect,infras
Culturesaredifferentbecausethelocationstheyexistinaredifferent.Somepeoplelivinginthedesertaregoingto
Overthepasttwodecades,countriesintheworldhavebecomemoreandmoreinterdependent,andnewtechnologieshaveerasedman
Theabilitytostoreknowledgemakescomputersdifferentfromeveryothermachine______invented.
Aneweraisuponus.Callitwhatyouwill:theserviceeconomy,theinformationage,theknowledgesociety.Italltranslates
ACubandiplomatwasdeportedfromtheUnitedStateslastweekendfor______.
FromachildIwasfondofreading,andallthelittlemoneythatcameintomyhandswaseverlaidoutinbooks.Pleasedwithth
WouldyoupleasecomeandhelpmewiththisformbecauseIdon’tknowhowto_________it.
TheflighttoShanghaiwillleavefromthis______attheairport.
There’samanatthereceptiondeskwhoseemsveryangryandIthinkhemeans______.trouble.
随机试题
天车与钢丝绳、游动滑车构成游动系统。()
试述保密措施设计应考虑的安全措施。
投资业务会计制度设计的首要目标是()
A.肺炎链球菌B.难辨梭状芽胞杆菌C.铜绿假单胞菌D.龟分枝杆菌E.厌氧球菌革兰染色阳性的细菌是
关于免疫细胞,错误的叙述是
患者,男,44岁。因误服大量巴比妥类药物入院。住院期间,患者呼吸呈周期性变化:呼吸由浅慢逐渐变为深快,然后转为浅慢,经过一段时间呼吸暂停,又重复上述变化,其形态如潮水起伏。该呼吸节律中呼吸变为深快的主要机制是
皮下注射部位错误的是
阅读一本《论语》,甚至是厚厚的《史记》,为什么有人能一目十行,不到几分钟就可讲出书中的内容?2014年10月,中科院上海生命科学研究院某课题组采用先进的光遗传方法,证实了“瞬间记忆”的幕后“操控者”为大脑内侧的前额叶——额头后面的一片大脑区域。当“瞬间记忆
被誉为“法条明审,科条简要”的封建成文法典是()。
在窗体中添加一个名称为Command1的命令按钮,然后编写如下事件代码:PrivateSubCommand1_Click()s=“ABBACDDCBA”ForI=6To2Step-2x=Mid(s,I,I
最新回复
(
0
)