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 prefix Mach is used to describe supersonic speed. It was named for Ernst Mach (1838-1916), a Czech-born Austrian physicist,
The prefix Mach is used to describe supersonic speed. It was named for Ernst Mach (1838-1916), a Czech-born Austrian physicist,
admin
2014-07-20
8
问题
The prefix Mach is used to describe supersonic speed. It was named for Ernst Mach (1838-1916), a Czech-born Austrian physicist, who contributed to the study of sound. When twice the speed of sound, it is Mach 2. When it is near but below the speed of sound, its speed can be designated at less than Mach 1. for example, Mach 90. Mach is defined as "the ratio of the velocity of a rocket or a jet to the velocity of sound in the medium being considered."
When a plane passes the sound barrier-flying faster than sound travels’ listeners in the area hear thunderclaps, but the pilot of the plane does not hear them.
Sound is produced by vibrations of an object and is transmitted by alternate increase and decrease in pressure that radiate outward through a material media of molecules--somewhat like waves spreading out on a pond after a rock has been tossed into it.
The frequency of sound is determined by the number of times the vibrating waves undulate per second and is measured in cycles per second. The slower the cycle of waves, the lower the frequency. As frequencies increase, the sound is higher in pitch.
Sound is audible to human beings only if the frequency falls within a certain range. The human ear is usually not sensitive to frequencies of fewer than 20 vibrations per second, or more than about 20,000 vibrations per second--although this range varies among individuals. Anything at a pitch higher than the human ear can hear is termed ultrasonic.
Intensity, or loudness, is the strength of the pressure of these radiating waves and is measured in decibels. The human ear responds to intensity in a range from zero to 120 decibels. Any sound with pressure over 120 decibels is painful to the human ear.
The speed of sound is generally placed at 1088 feet per second at sea level at 32 degrees Fahrenheit. It varies in other temperatures and in different media. Sound travels faster in water than in air, and even faster in iron and steel. It travels a mile in 5 seconds in air, it does a mile under water in 1 second, and it travels through iron in 1/3 second. It travels through ice cold vapor at approximately 4,708 feet per second; ice-cold water, 4,938; granite, 12,960; hardwood, 12,620; brick, 11,960, glass. 16,410 to 19,690; silver, 8,658; gold, 5,717.
Which of the following is a TRUE statement?
选项
A、Sound travels fastest through the hardest thing.
B、Sound travels at different speed in different temperatures and in different media.
C、Sound travels fastest in hottest temperature.
D、Sound travels fastest in coldest temperature.
答案
B
解析
根据最后一段第二句“音速在其他温度和在不同的介质中各不相同”,由此可知答案为B 。其他三个选项文中并没有提到,故排除。
转载请注明原文地址:https://jikaoti.com/ti/NSxMFFFM
0
专业英语四级
相关试题推荐
OnJanuary1stmanypeoplemakeaNewYear______.
Thesetwoareasaresimilar______theybothhaveahighrainfallduringthisseason.
______,heisnotcapableofteachingallsubjects.Afterall,nobodycouldbeanexpertonevery-thing.
Whileradiobroadcastingwasstill【C1】_____________itsearlystagethewonderoftelevisionwas【C2】_____________beingdevelope
IwasborninTuckahoe,TalbotCountry,Maryland.Ihavenoaccurateknowledgeofmyage,neverhavingseenanyauthenticreco
______canhelpbutadmitthatdrasticchangeshavetakenplaceinChinasincetheeconomicreform20yearsago.
At2P.M.onDec.5,1945,fiveNavybomberstookoffinperfectflyingweatherfromtheNavalAirStationatFortLauderdale,Fl
SputnikIwasthefirstartificialsatellite.Itcanbedescribedasanaluminum(1)______withadiameterof58centimetersand
Theheatinsummerisnoless_______hereinthismountainregion.
Johnmade______keysforthehouse:oneforhiswifeandoneforhimself.
随机试题
A.DDD型B.VVI型C.AAI型D.VOO型E.ICD型(2006年)反复发作性室性心动过速伴短阵意识丧失者,应首选的起搏器型号是
A.信念B.态度C.行为D.信息E.知识健康教育“知-信-行”模式中,基础是
头颈部放疗患者放疗前应进行的口腔治疗不包括
强心苷的药理作用的描述,正确的是( )
关于招标控制价及其编制的说法,正确的是()。【2011年真题】
根据《中华人民共和国民事诉讼法》的规定,下列关于督促程序的表述中,正确的是()。
当Excel中图表的数据源发生变化时,下列关于图表变化的描述,正确的是()。
阅读下面材料,回答问题。今天语文课的学习内容是一篇文言文课文。上课伊始,老师说:“这篇课文比较长,我们将用两节课学完。"说完,便转过身去板书。他刚写完课文题目,便听到有同学喊:“报告!”“什么事?”老师问。“老师,我不同意用两
罪犯在入狱前,我们会对其进行心理辅导,以便他们可以适应监狱的生活;在服刑期间,会通过劳动对他们进行改造,以便他们更好地赎罪:在出狱之前.也会对他们进行心理的疏导,以便他们能够更好地回归社会。因此有人说:“罪犯是监狱的作品”。对此你怎么看?
简述我国法律责任的归责原则。(2012年一法综一第31题)
最新回复
(
0
)