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
2024-09-29
35
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] Which of the following can serve as the best title of this passage?
选项
A、The Prefix Mach
B、The Speed of Sound
C、The Frequency of Sound
D、The Intensity of Sound
答案
B
解析
根据以上题的题解,不难看出本文的关键词是声音的速度,故答案为B 。C 和D 只涉及了其中一方面而已,A 文中并未提到。
转载请注明原文地址:https://tihaiku.com/zcyy/3779305.html
相关试题推荐
TheprefixMachisusedtodescribesupersonicspeed.ItwasnamedforErns
TheprefixMachisusedtodescribesupersonicspeed.ItwasnamedforErns
Howlonghasthemansufferedfromthesymptomshedescribed?[originaltext]M:G
TheprefixMachisusedtodescribesupersonicspeed.ItwasnamedforErnst
TheprefixMachisusedtodescribesupersonicspeed.ItwasnamedforErnst
TheprefixMachisusedtodescribesupersonicspeed.ItwasnamedforErnst
TheprefixMachisusedtodescribesupersonicspeed.ItwasnamedforErnst
Howlonghasthemansufferedfromthesymptomshedescribed?[br][originaltex
Howlonghasthemansufferedfromthesymptomshedescribed?[br][originaltex
Howlonghasthemansufferedfromthesymptomshedescribed?[originaltext]M:G
随机试题
Edisonwasagreat(science)______intheworld.scientist本题考查名词的运用。从句意上看Edison是个
Formostseniorstudentstherearemainlytwoalternatives:oneistofinda
About______offoreign-ownedcompaniesavoidedfederaltaxesaltogether.[br]
Everybodywantstogetwealthy.Intoday’s【B1】______world,makingmoneyor
下列情况对结构构件产生内力,哪一项不属于可变作用?( )A.吊车荷载 B.屋
由小肠上皮细胞合成并含有大量甘油三酯的血浆脂蛋白是A.LDL B.Lp(a)
患者,女,60岁,有反复尿路感染病史5年,3天前因劳累而复发,发症:小便淋沥不已
状态评价班人员应对()设备进行现场巡视检查后开展评价。500(330)kV$;
一般资料:求助者,男性,21岁,大学二年级学生。 案例介绍:求助者自述半年前因
投资项目决策分析与评价的基本要求包括贯彻落实科学发展观、资料数据准确可靠和()
最新回复
(
0
)