首页
登录
职称英语
The ability of falling cats to right themselves in midair and land on their
The ability of falling cats to right themselves in midair and land on their
游客
2023-11-14
35
管理
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. [br] 【C3】
选项
A、unless
B、until
C、when
D、after
答案
A
解析
根据句型结构和逻辑关系的分析,答案是A。
转载请注明原文地址:http://tihaiku.com/zcyy/3185000.html
相关试题推荐
Humanbeingshave______themselvestoverydiverseenvironmentswiththehelpof
Thenewstadiumhastheseating______of3,000people.A、powerB、capabilityC、ca
Humansareuniqueintheextenttowhichtheycanreflectonthemselvesand
Humansareuniqueintheextenttowhichtheycanreflectonthemselvesand
Humansareuniqueintheextenttowhichtheycanreflectonthemselvesand
Humansareuniqueintheextenttowhichtheycanreflectonthemselvesand
Humansareuniqueintheextenttowhichtheycanreflectonthemselvesand
Humansareuniqueintheextenttowhichtheycanreflectonthemselvesand
Humansareuniqueintheextenttowhichtheycanreflectonthemselvesand
Humansareuniqueintheextenttowhichtheycanreflectonthemselvesand
随机试题
Readthearticleaboutthecashbasicofaccounting.Choosethebestwordtofil
[originaltext]W:Sir,whatareyougoingtoorder?M:Justacupofcoffeeand
What’sthethemeofeachcontinentbasedontheroomsoftheclubhouse?ChooseS
[originaltext]TheUnitedNationsjustwrappedupaneventfocusedongender
技术部给采购部提供了一份采购产品的技术标准和要求,这份文件可被称作( )。A.
面神经颅外段的分支哪一个不正确() A.下颌支 B.颊支 C.
关于交易对手的国别风险识别,商业银行应当( )。A.对涉及敏感国家或地区的业务
属于头孢菌素类的抗生素是
下列关于基金登记的说法,错误的是()。A.基金份额登记具有确定和变更基金份额持
现代社会中,人们是在相对统一的时间里交往活动,这有利于节约社会成本,提高社会效率
最新回复
(
0
)