首页
登录
职称英语
The prefix Mach is used to describe supersonic speed. It was named for Ernst
The prefix Mach is used to describe supersonic speed. It was named for Ernst
游客
2024-09-28
10
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 0. 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 1, 088 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 is true?
选项
A、Sound travels fastest through the hardest things.
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“声音在不同温度和不同介质中的速度各不相同”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://tihaiku.com/zcyy/3777292.html
相关试题推荐
Whenthetragicaccidenthappened,thetrainwasgoingatits______speed.A、ful
TheprefixMachisusedtodescribesupersonicspeed.ItwasnamedforErnst
TheprefixMachisusedtodescribesupersonicspeed.ItwasnamedforErnst
Howlonghasthemansufferedfromthesymptomshedescribed?[br][originaltex
Howlonghasthemansufferedfromthesymptomshedescribed?[br][originaltex
Howlonghasthemansufferedfromthesymptomshedescribed?[originaltext]M:G
WhichofthefollowingworddescribestherelationshipbetweentheIndiansandt
Whichwordmaybestdescribethetwospeakers’positionsonintermarriage?[br]
She_____toseveralnewspaperstokeeptrackofcurrentevents.A、describesB、pres
Whatisthepurposeoftheprogramthedeandescribes?A、Tofindjobsforgraduat
随机试题
Wechildrenarenotfondof______(watch)adultfilms.watching
NBCmanagersarelongingtoseehow.theshowfaresinthe______.A、mobB、moanC、
Forthispart,youareallowed30minutestowriteashortessaybasedonth
施工现场暂时停止施工的,施工单位应当做好现场防护,所需费用有施工方承担。()
资料:甲公司目前有两个投资项目A和B,两个项目的折现率均为10%,所得税税率为2
《中国居民膳食指南》的核心思想包括( )。A.平衡膳食 B.制定营养素参
下列腧穴中,不属于督脉的腧穴是()A.腰阳关 B.哑门 C.承浆 D
《中小学教师专业标准》提出的基本理念是()。A.师德为先,学生为本,能力为重,
某地铁地上车站,建筑高度为18m,站台层与站厅层之间设有建筑面积为100㎡的商场
汽车轮胎上的沟纹的主要作用是( )。A.增加与地面的摩擦 B.排除雨水和泥水
最新回复
(
0
)