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
44
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] 【C12】
选项
A、showed
B、shows
C、show
D、had shown
答案
C
解析
照片虽然摄于1894年,但现在仍存在,因此用现在时,而且主语是复数,所以选C。
转载请注明原文地址:http://tihaiku.com/zcyy/3185009.html
相关试题推荐
ThereareseveralpossibleexplanationsforthegreaterjobstabilityinJapan__
Morethanonehundredguestsattendedthewedding______andenjoyedthemselves.A、
Whatistheprobabilityofthisevent______?A、tooccurB、occursC、occurringD、oc
Lightningbugscanblinkthemselvesbecauseofachemicalsubstance[br][origi
Lightningbugscanblinkthemselvesbecauseofachemicalsubstance[originaltex
Theability______isveryimportantforanyspeaker.A、tohearclearlyB、tobecle
Employeesshould______themselvesoftheopportunitytobuycheapsharesinthec
Highgradesaresupposedto______academicability,buthisactualperformance
Humanbeingshave______themselvestoverydiverseenvironmentswiththehelpof
Thenewstadiumhastheseating______of3,000people.A、powerB、capabilityC、ca
随机试题
[audioFiles]audio_eufm_j84_001(20082)[/audioFiles]A、Shedislikedskating,sosh
Fewhumanrecordssurviveforlong,the16000-year-oldPaleolithiccavepai
电力系统的接线图包括()。A.电气接线图 B.架空线接线图 C.变电站接线
某高速公路工程交工验收,检测人员需要对路面进行现场检测。该工程的路面为沥青混凝土
数字65代表()。A.小于67的值均符合要求 B.大于67的值均符合要求
A.简化口腔卫生指数(OHI-S) B.龈指数(GI) C.龈沟出血指数(S
下列不属于证券产品选择的基本原则的是()。A.效益与风险最佳组合原则 B
罗杰斯对“经验”的概念来源于现象学中的“现象场”,“现象场”是指( )。A.人的
A.在成牙本质细胞和矿化牙本质之间是一层未钙化的牙本质 B.胶原纤维较多,矿化
中央银行制度的建立,大致出于以下需要()。A.集中货币发行权的需要 B.代
最新回复
(
0
)