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
39
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] 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
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/3164737.html
相关试题推荐
Accordingtothespeaker,yogashouldNOTbedescribedas______[br][original
Angyaldescribedthecaseofamanwithadomineeringfatherwhoshowedextr
Angyaldescribedthecaseofamanwithadomineeringfatherwhoshowedextr
SputnikIwasthefirstartificialsatellite.Itcanbedescribedasanalum
SputnikIwasthefirstartificialsatellite.Itcanbedescribedasanalum
SputnikIwasthefirstartificialsatellite.Itcanbedescribedasanalum
SputnikIwasthefirstartificialsatellite.Itcanbedescribedasanalum
SputnikIwasthefirstartificialsatellite.Itcanbedescribedasanalum
SputnikIwasthefirstartificialsatellite.Itcanbedescribedasanalum
SputnikIwasthefirstartificialsatellite.Itcanbedescribedasanalum
随机试题
AuthorEmmaHeathcote-Jameshasspentnineyearslookingintoreal-lifeghos
TheMissAmericacelebration【C1】______asabeautycontestin1921,butnowp
[originaltext]M:Hi,Emily,whatdoyouthinkofourclassinChildren’sLitera
脓性指头炎的治疗包括()。A.局部热敷理疗 B.疼痛剧烈,指腹张力显著增高时
网络系统设计过程中,物理网络设计阶段的任务是( )。A.依据逻辑网络设计的要求
( )原则是基金管理人内部部门和岗位的设置应当权责分明、相互制衡。A.独立性
根据化学结构盐酸赛庚啶属于A:氨基醚类 B:三环类 C:丙胺类 D:咪唑类
某企业采购一批商品,货款总额为80000元,由于付款及时获得6%的现金折扣,则该
在郁证的治疗中强调精神治疗的重要性,认为“郁证全在病者能移情易性”,此说见于A.
自创的或者自身拥有的无形资产,根据其形成时发生的实际成本及该项资产具备的获利能力
最新回复
(
0
)