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
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] Decibel is
选项
A、the unit for measuring the4ntensity of sound.
B、the pressure of radiating waves.
C、the frequency of radiating waves.
D、the speed of sound.
答案
A
解析
根据第六段第一句“分贝是用来测量声音强度或大小的,即测量音量的单位”,故答案为A 。
转载请注明原文地址:https://tihaiku.com/zcyy/3779303.html
相关试题推荐
TheprefixMachisusedtodescribesupersonicspeed.ItwasnamedforErns
TheprefixMachisusedtodescribesupersonicspeed.ItwasnamedforErns
TheprefixMachisusedtodescribesupersonicspeed.ItwasnamedforErns
TheprefixMachisusedtodescribesupersonicspeed.ItwasnamedforErns
Howlonghasthemansufferedfromthesymptomshedescribed?[br][originaltex
TheprefixMachisusedtodescribesupersonicspeed.ItwasnamedforErnst
TheprefixMachisusedtodescribesupersonicspeed.ItwasnamedforErnst
Howlonghasthemansufferedfromthesymptomshedescribed?[br][originaltex
Howlonghasthemansufferedfromthesymptomshedescribed?[br][originaltex
Howlonghasthemansufferedfromthesymptomshedescribed?[br][originaltex
随机试题
[originaltext]ThankyouforcallingtheUniversityCareerManagementCentre(UC
Wereyouthefirstorthelastchildinyourfamily?Orwereyouamiddleor
A.单侧或双侧的痛温觉丧失,而触觉及深感觉完整或相对正常,肌萎缩明显 B.颈痛
女性,56岁,上腹不适嗳气1个月,进食如常,胃镜示:胃角小弯侧1cm×0.6cm
某医院统计某天求诊的病人,内科150人,外科90人,内外科都求诊的20人,这天一
西周设在王都的是国学,设在王都郊外六乡行政区中的地方学校是乡学。
某地区进行的吸烟与某种疾病关系的大量研究资料如下 根据该资料,比较吸烟和不吸烟
根据刑事法律制度的规定,剥夺政治权利是刑事责任中附加刑的一种,下列各项中属于具体
(2017年真题)2016年12月31日,某企业进行现金清查,发现库存现金短款3
招标准备阶段招标人的主要工作包括()。A.向建设行政主管部门办理申请招标手续
最新回复
(
0
)