首页
登录
职称英语
The prefix Mach is used to describe supersonic speed. It was named for Erns
The prefix Mach is used to describe supersonic speed. It was named for Erns
游客
2023-11-06
47
管理
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. [br] Which of the following can serve as the best title of this passage?
选项
A、The Prefix Mach
B、The Speed of Sound
C、The Frequency of Sound
D、The Intensity of Sound
答案
B
解析
根据以上题的题解,不难看出本文的关键词是声音的速度,故答案为B 。C 和D 只涉及了其中一方面而已,A 文中并未提到。
转载请注明原文地址:https://tihaiku.com/zcyy/3164741.html
相关试题推荐
TheprefixMachisusedtodescribesupersonicspeed.ItwasnamedforErns
TheprefixMachisusedtodescribesupersonicspeed.ItwasnamedforErns
TheprefixMachisusedtodescribesupersonicspeed.ItwasnamedforErns
TheprefixMachisusedtodescribesupersonicspeed.ItwasnamedforErns
Howlonghasthemansufferedfromthesymptomshedescribed?[originaltext]M:G
Whenthetragicaccidenthappened,thetrainwasgoingatits______speed.A、ful
TheprefixMachisusedtodescribesupersonicspeed.ItwasnamedforErnst
TheprefixMachisusedtodescribesupersonicspeed.ItwasnamedforErnst
TheprefixMachisusedtodescribesupersonicspeed.ItwasnamedforErnst
TheprefixMachisusedtodescribesupersonicspeed.ItwasnamedforErnst
随机试题
In2004,theAuburnHousingAuthoritybecamethefirstauthorityinMainean
[originaltext]Whydowecry?Canyouimaginelifewithouttears?Notonlyd
InLondon,overhalfofthehomesbuiltbetween1919and1980hadonegarage
[originaltext]Youshouldnotfearspidersbecauseoftheirpoison.Ofallt
建筑屋面雨水排水工程的溢流设施,下述哪项是错误的?( )A.溢流口 B.溢流
游客在长途交通工具运输途中突患重病,全陪应该()A.向患者亲属了解患病旅游者的病
患者,女,45岁,诊断为特发性血小板减少性紫癜,正规泼尼松治疗1年后,血小板20
比较《防洪标准》和《城市防洪工程设计规范》,判断下列说法中错误的是()。A.
X光设备应接地,接地电阻不应大于()。 A.30ΩB.20ΩC.15Ω
关于现金流量图绘制规则说法,错误的是()。A.横轴为时间轴,整个横轴表示经济系
最新回复
(
0
)