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
2023-11-20
19
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 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. [br] 【C3】
选项
A、unless
B、until:
C、when
D、after
答案
A
解析
转载请注明原文地址:https://tihaiku.com/zcyy/3204560.html
相关试题推荐
Humanity’shighlydevelopedabilitytocommunicateverballyisouressence.
Humanity’shighlydevelopedabilitytocommunicateverballyisouressence.
Humanity’shighlydevelopedabilitytocommunicateverballyisouressence.
Humanity’shighlydevelopedabilitytocommunicateverballyisouressence.
Humanity’shighlydevelopedabilitytocommunicateverballyisouressence.
Humanity’shighlydevelopedabilitytocommunicateverballyisouressence.
Humanity’shighlydevelopedabilitytocommunicateverballyisouressence.
Allpeoplehavesomeabilitytomanagetheirhealthandthehealthofthose
Allpeoplehavesomeabilitytomanagetheirhealthandthehealthofthose
Allpeoplehavesomeabilitytomanagetheirhealthandthehealthofthose
随机试题
He_______inLondonformorethantenyears,buthehasneverregrettedhisfin
PASSAGETHREE[br]Whatisthemainideaofthispassage?Ittellsstoriesofsom
[audioFiles]audio_ehbm_j17001(20082)[/audioFiles]A、Thatwillbewonderful.B、It
期刊出版单位不得擅自转让( )。A.融资赞助权 B.封面设计权 C.编辑出
Haveyoueverhadtodecidewhethertog
砂的相对密度是表征砂紧密程度的指标。
关于卵磷脂小体,错误的是()。A.圆形或卵圆形 B.大小均匀 C.折光性强
Addison病常伴有A.皮肤色素沉着 B.高血糖 C.低血钾 D.低血钙
某基金经理持有30%国债、70%股票的投资组合。若预计股票市场将走强,则运用转移
政府公共部门与非公共部门合作过程中,让非公共部门所掌握的资源参与提供公共物品。这
最新回复
(
0
)