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
33
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
[originaltext]M:Next.Uh,yourpassport,please.W:Okay.M:[23]Uh,whatis
D
请简要回答现代儿童观的含义。
下列措施中可增加肠道氨的产生和吸收的是A.限制蛋白 B.新霉素口服 C.50
A.竹茹、茯苓B.人参、甘草C.竹叶、生姜D.竹茹、甘草E.半夏、竹茹温胆汤与橘
下列不属于对抗同贮养护技术的是A.泽泻、山药与牡丹皮同贮防虫保色 B.藏红
多式联运经营人可以分为( )和有船经营人。 A.有车经营人 B.无船
在解决问题的方法上,社会工作不但强调社会秩序的重要性,也强调不尽合理的()会造
统计指标一般包括()。A:相对指标B:总量指标C:绝对指标D:平均指标E
关于基金信息披露的表述,不正确的是()。A:基金信息披露是一种自愿性信息披露B
最新回复
(
0
)