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
An airplane flies because its wings push down on the air flowing past them, and in reaction, the air pushes up on the wings. Whe
An airplane flies because its wings push down on the air flowing past them, and in reaction, the air pushes up on the wings. Whe
admin
2010-02-05
28
问题
An airplane flies because its wings push down on the air flowing past them, and in reaction, the air pushes up on the wings. When an airplane is level or rising, the front edges of its wings ride higher than the rear edges. The angle the wings make with the horizontal is called the angle of attack. As the wings move through the air, this angle causes them to push air flowing under them downward. A sleeper angle of attack will cause the wings to push more air downward. The third law of motion voiced by English physicist Isaac Newton states that every action produces an equal and opposite reaction. In this case, the wings pushing air downward is the action, and the air pushing the wings upward is the reaction. This causes lift, the upward force on the plane, Lift is often explained using Bernoulli’s principle, which states that, in some circumstances, a faster moving fluid(流体) (such as air)will have a lower pressure than a slower moving fluid. The air on the top of an airplane wing is at a lower pressure than the air underneath the wing, but this is an effect of lift, not its cause.
Lift is one of the four primary forces acting upon an airplane. The others are weight, thrust, and drag. Weight is the force that offsets lilt. because it acts in the opposite direction. The weight of the airplane must be overcome by the lift produced by the wings, if an airplane weighs 4.5 metric tons, then the lift produced by its wings must be greater than 4.5 metric tons in order for the airplane to leave the ground. Designing a wing that is powerful enough to lift an airplane off the ground, and yet efficient enough to fly at high speeds over extremely long distances, is one of the marvels of aircraft technology.
选项
答案
Why does an airplane fly?
解析
根据第一句话“An airplane flies because its wings push down on the air flowing past them,and in reaction,the air pushes up on the wings.”和全篇文章的意思得出。
转载请注明原文地址:https://kaotiyun.com/show/xOqK777K
本试题收录于:
大学英语三级A级题库大学英语三级分类
0
大学英语三级A级
大学英语三级
相关试题推荐
Ineedtochecktheinformation,________Marysaysitiscorrect.
Colorsaresometimescalledhot,cold,orneutral(中性的).Redandyellowaresaidtobehotcolorsbecausetheymakearoomwarme
PartyA:ShanghaiInternationalTradeCorporationPartyB:BritishAARBankGroupJVCompany:AARTradeCompanyNotes:APar
Thefollowingisanadvertisement.Afterreadingit,youarerequiredtocompletetheoutlinebelowit(numbered46throughnumb
Theproceduresforopeningacheckingaccount______.Whatisthispassagemainlyabout?
Inthefirstparagraph,thewritertriestotellusthatpeopleTheword"shaky"(Line1,Para3)mostprobablymeans"______"
I’mthe(little)______experiencedofallthedoctorshere.
Inordertoimproveourspeaking,whatshouldwedo?Weshould______toourclassmatesandEnglishteachersdaily.Whatshou
Theauthorpointsoutthatthefatherdiaperinghisfirstbornsonwaswrongbecause______.Whatdoesthesentence"Heisaglu
Theword"surplus"inthelastsentenceofPara.2meansWhichofthefollowingisNOTtrueaccordingtothepassage?
随机试题
[2008年,第120题]价值工程的价值是()。
背景A公司参与远离所在地炼钢厂的机电安装工程总承包的投标,投标前做了如下工作:1.分析了招标文件工程范围,本工程含机械设备安装、电气及自动化系统安装、钢结构及非标准件制作安装、工业给水排水施工、防腐及保温工程、筑炉工程。并分析本公司施工技术力量
“包装物”的借方登记()。
现金在商业银行资产负债中属于()。
2017年8月,一家新开业的小型微利商业企业,为了拓展市场,从开业之日起至12月31日销售商品一律实行买一赠一活动,开业5个月销售商品共计取得不含税销售收入225万元,赠送商品的不含税市场价格为15万元,全部销售商品和赠送商品的成本为180万元,应扣除的税
在对债务重组进行账务处理时,债权人对债务重组的应收账款是否冲销其已计提的坏账准备,并不影响债务重组年度净损益的数额。 ( )
旅游安全事故主要包括()
已知数据表A中每个元素距其最终位置不远,为节省时间,应采用的算法是______。
Itwaslateintheafternoon,andIwasputtingthefinaltouchonapieceofwritingthatIwasfeelingprettygoodabout.Iwa
ImaginethatanIrishmarketingfirmisdoingresearchinyourcountry.Youhaveagreedtoparticipateinatelephoneinterview
最新回复
(
0
)