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
40
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/3777289.html
相关试题推荐
TheprefixMachisusedtodescribesupersonicspeed.ItwasnamedforErnst
TheprefixMachisusedtodescribesupersonicspeed.ItwasnamedforErnst
Howlonghasthemansufferedfromthesymptomshedescribed?[br][originaltex
Howlonghasthemansufferedfromthesymptomshedescribed?[br][originaltex
Howlonghasthemansufferedfromthesymptomshedescribed?[originaltext]M:G
WhichofthefollowingworddescribestherelationshipbetweentheIndiansandt
WhichofthefollowingworddescribestherelationshipbetweentheIndiansandt
WhichofthefollowingworddescribestherelationshipbetweentheIndiansandt
Whichwordmaybestdescribethetwospeakers’positionsonintermarriage?[br]
Whatwillthestudentsberequiredtodointhecoursethewomandescribed?A、Pa
随机试题
Thisisamarketinwhichenterprisingbusinesses______forthedemandsofteen
TestshaveconfirmedthatfourpeopleinWisconsincontractedthemonkeypox
【B1】[br]【B10】risen→raised本题考查词汇辨析。raise是及物动词可以用被动语态。rise是不及物动词,没有被动语态。
外卖促销活动的对象通常有( )。A.外国的商业机构、办事处 B.外商企业
软化点试验过程中,对试验结果产生影响的因素包括()A.试验起始温度 B.
某商业银行以为客户计划投资黄金,则银行从业人员可以建议客户选择的投资方式有(
关于我国社区治理,下列理解错误的是:A.社区治理的主体强调唯一性 B.社区
脑脊液漏禁忌耳鼻冲洗的目的是避免()。A.脑病 B.头痛 C.颅内压下降
贷款发放后,关于对保证人保证意愿的监控,做法错误的是()。A.应密切注意保证人的
银行承兑汇票的承兑银行,应当按照票面金额向出票人收取()的手续费。A:千分之一
最新回复
(
0
)