首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
The ability of falling cats to right themselves in midair and land on their feet has been a source of wonder for ages. Biolo
The ability of falling cats to right themselves in midair and land on their feet has been a source of wonder for ages. Biolo
admin
2009-01-05
35
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 speeded up, or the cat’s fall slowed down for the phenomenon to be 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 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 thousand fold.
【C12】
选项
A、showed
B、shows
C、show
D、had shown
答案
C
解析
转载请注明原文地址:https://www.kaotiyun.com/show/ycBK777K
0
专业英语四级
相关试题推荐
PositiveforYouthaimstoplaceteenagersandyoungpeopleatitsheart.Thereistheaccurateexpectationteenagersthemselves
PositiveforYouthaimstoplaceteenagersandyoungpeopleatitsheart.Thereistheaccurateexpectationteenagersthemselves
PositiveforYouthaimstoplaceteenagersandyoungpeopleatitsheart.Thereistheaccurateexpectationteenagersthemselves
PositiveforYouthaimstoplaceteenagersandyoungpeopleatitsheart.Thereistheaccurateexpectationteenagersthemselves
PositiveforYouthaimstoplaceteenagersandyoungpeopleatitsheart.Thereistheaccurateexpectationteenagersthemselves
Formany,thepursuitofhappinessisalsothepursuitofprosperity.PartoftheAmericandreamistheabilitytoprovide【M1】__
Formany,thepursuitofhappinessisalsothepursuitofprosperity.PartoftheAmericandreamistheabilitytoprovide【M1】__
Formany,thepursuitofhappinessisalsothepursuitofprosperity.PartoftheAmericandreamistheabilitytoprovide【M1】__
随机试题
下面对牺牲阳极材料性能要求表述不正确的是()。
根据污染物在水环境中输移、衰减特点以及它们的预测模式,将污染物分为()。
基金份额持有人大会应当由代办()以上基金份额的持有人参加。
下列各还款方式中,各定期还款额逐次递减的有()。
中国人民银行对()有权进行检查监督。
某企业2014年度利润总额80万元,通过公益性社会团体向某灾区捐赠2万元,直接向某学校捐款5万元。根据企业所得税法律制度的规定,该企业在计算企业所得税应纳税所得额时,可以扣除捐赠支出()万元。
有专家指出,社交媒体是一把双刃剑,既有利于各国政府及时调整政策、改善服务和塑造形象,又可能被当作一种传播谣言、引发动乱、助长恐怖主义和仇恨犯罪的工具。因此,微博、推特等社交媒体正在全国范围内迅速普及和壮大,已成为影响世界政治的新变量。下列选项如果为真。最能
社会和谐是中国特色社会主义的()
Abeginnerinthestockmarketshouldstayclearofvolatileinvestmentsofallkinds.
A、Hehasalreadygottheresult.B、Hetookittwoweeksago.C、Theresultisstillunknown.D、Thetestwillbeavailable.C
最新回复
(
0
)