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
30
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] According to this passage, "Mach" refers to
选项
A、the ratio of the air speed of an aircraft to the speed of sound.
B、a machine.
C、a Czech-born Australian physicist.
D、the pilot of the plane.
答案
A
解析
第一段最后一句提到,马赫(Mach)是火箭或飞机在空中的速度与声速的比率,由此可知答案为A 。
转载请注明原文地址:https://tihaiku.com/zcyy/3164736.html
相关试题推荐
TheprefixMachisusedtodescribesupersonicspeed.ItwasnamedforErns
TheprefixMachisusedtodescribesupersonicspeed.ItwasnamedforErns
Howlonghasthemansufferedfromthesymptomshedescribed?[originaltext]M:G
Whenthetragicaccidenthappened,thetrainwasgoingatits______speed.A、ful
TheprefixMachisusedtodescribesupersonicspeed.ItwasnamedforErnst
TheprefixMachisusedtodescribesupersonicspeed.ItwasnamedforErnst
TheprefixMachisusedtodescribesupersonicspeed.ItwasnamedforErnst
TheprefixMachisusedtodescribesupersonicspeed.ItwasnamedforErnst
Howlonghasthemansufferedfromthesymptomshedescribed?[br][originaltex
Howlonghasthemansufferedfromthesymptomshedescribed?[originaltext]M:G
随机试题
Inonesense,wecantracealltheproblemsoftheAmericancityback【C1】___
[originaltext]TheWorldSantaClausCongressisdesignedforpeoplewhoenjoyp
在商标评审行政诉讼过程中,商评委不得再向原告或第三人收集证据。()
表格的形态样式主要有()等。A.全线表 B.续排表 C.无线表 D.三维
动脉导管未闭与室间隔缺损X线检查的主要区别点是A.肺动脉膨隆 B.肺野充血
近年来,社会上流行这样一种说法:“不要让孩子输在起跑线上”。对于这种说法,你怎么
牛黄清心丸有的功效是A.清热解毒,安神定志B.清热开窍,安神祛痰C.清热解毒,开
1.公司员工关爱社会要从倡导文明、积极参加文明创建活动开始,做到()。
下列关于江恩理论的说法,正确的是()。A.构造圆形图预测价格的具体点位 B.
(2021年真题)传统汽车制造企业华阳公司实施数字化战略转型,提高电子商务采购金
最新回复
(
0
)