首页
登录
职称英语
An Interesting Phenomenon The ability of falling cats to right t
An Interesting Phenomenon The ability of falling cats to right t
游客
2023-12-14
8
管理
问题
An Interesting Phenomenon
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 adaptation by natural selection, but for physicists it bordered on the miraculous. Newton’s laws of motion assume that the total amount of spin of a body cannot change unless an external torque speeds it up or slows it down. If a cat has no spin when it is released and experiences no external toque, it ought not to be able to twist around as it falls.
In the speed of its execution, the righting of a tumbling cat resembles a magician’s trick. The gyrations of the cat in midair are too fast for the human eye to follow, so the process is obscured. Either the eye must be speeded up, or the cat’s fall be slowed down for the phenomenon to be observed. A century ago the former was accomplished by means of high -speed photography using equipment now available in any pharmacy. But in the nineteenth century the capture 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 each, one from the side and one from behind, show a white cat in the act of righting itself. Grainy and quaint though 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 clockwise, the rear and tail-twist counterclockwise, so that the total spin remains zero, in perfect accord with Newton’s laws. Halfway down, the cat pulls in its legs before reversing its twist and then extends them again, with the desired end result. The explanation was that while no body can acquire spin without torque, a flexible one can readily change its orientation, or phase. Cats know this instinctively, but scientists could not be sure how it happened until they increased the speed of their perceptions a thousand fold. [br] Why are the photographs mentioned referred to as an "experiment"?
选项
A、The photographs were not very clear.
B、The purpose of the photographs was to explain the process.
C、The photographer used inferior equipment.
D、The photographer thought the cat might be injure
答案
B
解析
第二段最后一句以及后面详细的摄影过程说明十九世纪人们通过高速的摄影技术和设备来做“科学实验”以便观察并解释这个有趣的想象,因为只有摄影才能记录下如此快的动作,故正确答案为B。
转载请注明原文地址:https://tihaiku.com/zcyy/3272562.html
相关试题推荐
Beforeconsideringthisquestionitisinterestingtoreviewbrieflytheevolu
Beforeconsideringthisquestionitisinterestingtoreviewbrieflytheevolu
Beforeconsideringthisquestionitisinterestingtoreviewbrieflytheevolu
Beforeconsideringthisquestionitisinterestingtoreviewbrieflytheevolu
Beforeconsideringthisquestionitisinterestingtoreviewbrieflytheevolu
Beforeconsideringthisquestionitisinterestingtoreviewbrieflytheevoluti
Beforeconsideringthisquestionitisinterestingtoreviewbrieflytheevoluti
Beforeconsideringthisquestionitisinterestingtoreviewbrieflytheevoluti
Beforeconsideringthisquestionitisinterestingtoreviewbrieflytheevoluti
Beforeconsideringthisquestionitisinterestingtoreviewbrieflytheevoluti
随机试题
Animalperformmanyusefulandentertainingjobs.Dogsareparticularvaluab
Accordingtothepassage,ifadriverfallsasleepinoneofthetestcars,____
Itseemsindividualcancercellssendoutthesamedistresssignalsaswo
急性巴比妥类药物中毒,重度中毒时一般服用量为催眠剂量的A.1~2倍 B.2~5
网络集群行为,指一定数量的相对无组织的网民,在网络环境中或在网络传播影响下,针对
政府发行债券所筹集的资金可用于()。 ①.协调财政资金短期周转 ②.弥
位于乳突前下方与下颌角之间的凹陷中的腧穴是A.角孙 B.翳风 C.翳明 D
《国家中长期教育改革与发展规划纲要《2010—2020》提出,均衡发展是义务教育
单项薪酬制度包括()。A.工资制度 B.奖励制度 C.福利制度 D.津贴
理学重道德的修养固然不错,其对于中国社会日后发展贡献,也不容忽视,但不能都认,理
最新回复
(
0
)