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
2023-11-04
46
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] Sound is produced by
选项
A、vibrations of an object passing through the air.
B、spreading of waves after a rock being tossed into a pond.
C、thunders.
D、a flying plane.
答案
A
解析
由题干关键词,将信息定位于第三段第一句Sound is produced by vibrations of an object and is transmitted by alternate increase and decrease in pressure“声音产生于物体的震动…”,由此可知答案为[A]。
转载请注明原文地址:https://tihaiku.com/zcyy/3157123.html
相关试题推荐
TheprefixMachisusedtodescribesupersonicspeed.ItwasnamedforErns
TheprefixMachisusedtodescribesupersonicspeed.ItwasnamedforErns
Howlonghasthemansufferedfromthesymptomshedescribed?[br][originaltex
Howlonghasthemansufferedfromthesymptomshedescribed?[originaltext]M:G
Whenthetragicaccidenthappened,thetrainwasgoingatits______speed.A、ful
TheprefixMachisusedtodescribesupersonicspeed.ItwasnamedforErnst
TheprefixMachisusedtodescribesupersonicspeed.ItwasnamedforErnst
TheprefixMachisusedtodescribesupersonicspeed.ItwasnamedforErnst
Howlonghasthemansufferedfromthesymptomshedescribed?[br][originaltex
Howlonghasthemansufferedfromthesymptomshedescribed?[originaltext]M:G
随机试题
Whichofthefollowingunderlinedpartsindicatesasubject-verbrelation?A、The
A
--WhydoesJohnspeakthrougheverydisc
重度营养不良引起水肿的主要原因是A.心功能不全 B.肾功能不全 C.低蛋白血
电力电缆红外测温时,带电运行时间应该在()以上,宜在设备()状态下进行。
并解列检查负荷分配,并在该项的末尾记上实际()数值。 (A)电压
道德是分领域和层次的。道德中的社会公德,是维护公共秩序的重要手段。在人类社会发展
一般来说,()会提髙能力倾向测验的成绩。 (A)较低的焦虑(B)较高的焦虑
下列流水施工参数中,用来表达流水施工在施工工艺方面进展状态的是()A、流水步距
(2013年真题)建设工程项目进度控制中,业主方的任务是控制整个项目( )的进度
最新回复
(
0
)