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习题练习：Physics Unit12: Sound
本习题练习试卷来源于51fly国际课程 (https://51fly.win)， 为试卷打印版，您也可以在网站平台(https://autoconfig.51fly.win/)直接 访问本试卷的在线电子版并查看正确答案与解析，搜藏保存任意题目到收藏集。 访问方法: 平台首页左上角"通过试卷号快速访问"输入试卷号 70，并点击直达试卷；或浏览器地址栏内直接输入本试卷链接 https://autoconfig.51fly.win/test70.html  教师使用本平台可以抽题组卷或一键复制他人试卷，布置为在线考试或在线作业，全自动判分成绩一键排序导出，省时省力。
 作者: physics  发布日期: 2022-09-26 09:56    总分: 87分  得分: _____________

答题人: 游客未登录  开始时间: 22年08月07日 09:59  切换到: 整卷模式

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1#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Which of the following is a fdy /*rsc) 3supalse statement?

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2#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  In general, sound is conducted8e9/gs hi8ed e fastest through

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3#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  What is the speed of sound in a s cw8-sqbt(l g z85f/ pty0-ld,rdz8s vteel rod?

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4#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  As the temperature of zhv h9et8o;k/mg,5 kpthe air increases, what happens to the velocity of sound? (Assume that all other factors remain com85 h9otzkgeh; pk,/vnstant.)

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5#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Compared to the velocity of a 400 Hz sound, the velocity of a 200 Hz sound thyy06 i m3 g.e7mq a b58vl2e3eeoh1fkurougmea5vby.0o1ege i37y kq3h26 fu8 melh air is

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6#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Compared to the wavelength of a 400dsy7)gobz4 r3 Hz sound, the wavelength of a 200 Hz sound ins7ob3d4zry g) air is

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7#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Sound vibrations with frequencies greate ilz. kc3s;ac*r than 20,000 Hz are called

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8#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Sound vibrations with frequency less than 20 Hz are call63:-n(:nnpvvw:b 8fe 0znc7 nn ug qhfed

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9#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Suppose that a sound source is emitting wavoy2 5g d-:/w6zxheh ehes uniformly in all directions. If you move to a point twice as far away from the source, the fr-d6woezhg /hx h 5y:2eequency of the sound will be

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10#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  For spherically diverging waves, intens90 qp8abik k,hity is proportional to

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11#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  The intensity of a po47/zw+ us 88bqjfdlsk int source at a distance d from the source is I. What is the intensity at a dista us/wbf7q8jdsl +zk84nce 2d from the source?

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12#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  You double your distance from a sound source that is radiating equally i20 *+gpbcftz.x k)mha n all directions. What happens to the intensity of the sounx mck*)p20bh f.+tg azd? It reduces to

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13#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  You double your distance from a sound source that isq42(0trdq2atyilu l, radiating equally in all directions. What happens to the intensity level of the2r(yq 0atil t u42q,dl sound? It drops by

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14#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Which of the following increases anrzlbh9/+j x7s a sound becomes louder?

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15#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  You move slowly toward a speaker emitting a pure tone. What charfdu;leu e9frbk15,;lh)8z tpw2 b 0m cacteristic of the sound u2bwldup f8 cfl0e9; hz1km5 )e,;brtincreases?

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16#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  What determines "loudness" c m2o5eb/0apglzyz86 gvgd ts+r)f 6wd3 4ce4of a musical note?

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17#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  What determines the 0a0:zlwrxx gw;*rdf8ih ;(ns7-m zro"pitch" of a musical note?

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18#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  When sound passes from air into waters52jfp1 c5 lgu

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19#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Pressure and displacement waves ac1(r c+ufnul(n, knw3 re

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20#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Consider the standing wave on a gu:nhmhj)n x7 0n,pa (wen t5s2ritar string and the sound wave generated by the guitar as a result of this vibration. What do these two waves have in commor)jn x(2hen50p7hs :n,w amntn?

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21#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  In a resonating pipe which is open at bothzz d7(oiyhs0oc6v :.q ends, there

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22#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Consider an open pipe of length L. 0h kh/6gw6o 4 xqgh*qc What are the wavelengths of the three lowest tones produced by this piwg/h0qg*6 h koq46x hcpe?

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23#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  The lowest tone to resonate in an open pvahc610 wym +hk:i awl1hs3r)t k)de -ipe of length L is 200 Hz. Which one of the following frequencies will not res1h +kl eki )ym aw a)60rc:h13w-hsdvtonate in the same pipe?

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24#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  An open pipe of length L is resonating at its fundamental frequency. Which staonzh 4vh yr82,hyrc .2temenrh8yn4o, z y22vhcrh .t is correct?

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25#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  In a resonating pipe which is open at one end and closed at :qzg.q3xsm-:kri h4oqo 1d+u the other, there

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26#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Consider a closed pipe of lenu-w txyy6 cxi b)vhx3+3;h )ns r2yz4ngth L. What are the wavelengths of the three lowest tones produced b3vuy )3bxxihyr- 62 sn ctx;nz 4)y+why this pipe?

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27#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  The lowest tone to resonate in a closed pipe ofx0 gm8hk hbj9uya5; j6 length L is 200 Hz. Which of the followin a8 j9mjghb5;huk6x0 yg frequencies will not resonate in that pipe?

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本习题练习题目来源于51fly国际课程 (https://51fly.win)，学生可刷题练习，扫右侧二维码或加微信skysky1258，获取更多资料
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28#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A pipe of length L closed at one end is rbyotm;o/9i32 u3k iud9 j*zjh fi+ qu*esonating at its fundamental frequency. Which statement is cor*ioo9ut 3b+yqjdzj i*9m;i 3u/f 2uhkrect?

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29#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A person stands between two speakers driven by the same source. Each speaker p+4 o+p obuvihxw9(j r-roduces a tone with a frequi hbv o9-prw(+ujox4+ency of 200 Hz on a day when the speed of sound is 330 m/s. The person is
1.65 m from one speaker and 4.95 m from the other. What type of interference does the person sense?

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本习题练习题目来源于51fly国际课程 (https://51fly.win)，学生可刷题练习，扫右侧二维码或加微信skysky1258，获取更多资料
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30#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  In order to produce beats, the two sound8ifjn jmixj,p 4.zrtiyo668-py :cs. waves should have

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31#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Two pure tones are sound2orz n1 .nd8rwc1 ,1d1iqftkded together and a particular beat frequency is heard. What happens to the beat frequen1.d 1dnqi df2rz,8 1cw1rkn otcy if the frequency of one of the tones is increased?

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32#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  The Doppler shift explainf6 *kj-ho4pe ls

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33#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A sound source approaches a stationary observer. The frequency t/w-s9ntzzc 9m- 3aoaheard by the obsermcsa9o/ -n39 -z wazttver is

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34#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A sound source departs from f x-yb: g.uit41d9r4c-epzcwa stationary observer. The frequency heard by the ob.t4gxp uer 1wzb--4f:cdi 9cyserver is

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35#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  If a jet plane were to double its MACH-speed, its half-s 9f yn2. 5vjp e4hyknw.bcg57angle will decrease by a factor owh7.25bcgp jyn ey9s4k.5v fnf:

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36#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  The speed of an ultr347s(llbq 1:kc1 sysyh wsd x5asonic sound of frequency 45 kHz in air is 352 m/s. What is the air twcxs bh41ql7 sysl1 5skd:3(yemperature?

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37#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  What is the ratio of the speed of soundq jp.w(c;yin,5v5l4y oil w, s in air at $0 \; ^{\circ}C$ to the speed at $100 \; ^{\circ}C$?

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本习题练习题目来源于51fly国际课程 (https://51fly.win)，学生可刷题练习，扫右侧二维码或加微信skysky1258，获取更多资料
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38#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  On a day when the speed of sound idjzao:vvftjh0 d9u**89: yjczfq+ 2 wn air is 340 m/s, a bat emits a shriek whose echo reaches it 0.0250 s later. How far away was the object that refl0wjyvff+2ju8 d:cj a vztz9q*o9h* d:ected back the sound?

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39#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  You shout at a cliff, and hear the echo in 4.00 s. e wc8a1;)vrgu2i/ja5yvx w0k The temperature is $0 \; ^{\circ}C$. How far away is the cliff?

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40#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  If you hear thunder 5.0 s after seeing aj:ggta )5:dpt0e p,b b)dgz* e+* qpfa flash of lightning, the distance to the ligh* b0d5:e:ppazgqteftjg) +)* g,a dpbtning strike is about

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41#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  An echo is heard 2.0 s from a cliff on a day the temperature is f40.prt+xmm /vpmw- y $15 \; ^{\circ}C$. Approximately how far is the cliff from the observer?

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42#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  On a $30 \; ^{\circ}C$ day, there is an explosion. The sound is heard 3.4 s after seeing the flash. How far away was the explosion?

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43#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  You drop a stone into a deep well and hear the splash 2.5 s later9rk cb+er,3 th. How deep is the well? (Ignore air ber9t,3hc+rk resistance, and assume the velocity of sound is 340 m/s.)

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44#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  The wavelength in air of a vfkf )8n1o)r 2k:vmk csound wave of frequency 500 Hz is

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45#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Sound traveling in air at 5+odu/jk60cw w;ktvl $23 \; ^{\circ}C$ enters a cold front where the air temperature is $2 \; ^{\circ}C$. If the sound frequency is 1500 Hz, determine the wavelength in the warmer air and in the colder air.

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46#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  What is the intensity level of a sound with iug3oay8p grn 1doo:;.ntensity $10^{-3} \; W/m^{2}$?

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47#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  What is the intensity of a v :k zwu:q-v;w70-dB sound?

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48#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  What is the ratio of the intensities of two soundsji2 gg p3,wz2 4:tsgsy;vto6h with intensity levels of 70 dB andwy43z s6g: jg;t,sgit hp22ov 40 dB?

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49#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  The intensity level by 15 engines in a garageu(qk4p vb tjc-6m: k5c is 100 dB. What is the intensity level generated bqt:mc-6 ub 5k(pcv4jk y one engine?

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50#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  The intensity at a distance of 6.0 m from a sourcem0e( tf1 ny:hxb z fxc1*re)2z7aw,f i that is radiating equally in all directionx, mnf*01tw(zxh :7 brfc1 2)aifzyees is
$6.0 \times 10^{-10} \; W/m^{2}$. What is the power emitted by the source?

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51#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  The intensity at a distance of 6.0 iz6 - cktgzl5a-2z:wwm from a source that is radiating equally in all direc-wz56- liza tc2 zgkw:tions is
$6.0 \times 10^{-10} \; W/m^{2}$. What is the intensity level in dB?

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52#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A barking dog delivers about 1 mW of power, which is assumed to be uniform1,m fr,b 8.uy +m: 6wj5vqsjps(v ol,b y0dplmly distributed in all directions. What is the ,5 ps :d0 mb(uv,w s lyf6.o,1pljqvmrj+ybm8intensity level at a distance 5.00 m from the dog?

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53#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  The intensity level is 65 dB at a distance 5.00 m f /ktf3x* -yzaqrom a barking dog. What would be the3/yx*za-tkf q intensity level if two identical dogs very close to each other are barking?

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54#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  At a distance of 15 m4ano mb 3xc,hn)5oyp: from a sound source the intensity level is 60 dB. What is the intensity level (in dB) at a point 2.0 m from the source? Assume that the source radiate ny)ha4mb,:ncpox o3 5s equally in all directions.

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55#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  The sound intensity level 5.0 m from a point source is 95 dB9 n7a pc,i;x*rra36 mw txzx.b. At what distance will it wxrxtra*6x , mp9.n3ziba 7;cbe 75 dB?

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56#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  The third harmonic of a complex tone has a frequency of 1200 Hz. Whachd,e6:*91wlolo m m wzzu8m7t is the frequency of the fouww:9m68od z 17 u,zmm*col elhrth harmonic?

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57#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  The frequency of the third harmonic oj ;t+vd 84a9ef)vfk cwf an open pipe is 900 Hz. What is the length of the8evjvc;9w4adkt+ f) f pipe?

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58#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  The lowest tone to resonate in an open pipe of length L is7taxb46 ns8r p 400 Hz. What is the frequency of the l7n8 ras6bt 4pxowest tone that will resonate in an open pipe of length 2L?

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59#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  An organ pipe open at bot: zii5gt :n 7xy.hqub+h ends has a length of 0.80 m. If the velocity of sound in air is 340 m/s, what is the frequency of the secy:g.ih 5bt: +xzi nu7qond harmonic?

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60#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A 3.00-m long pipe is in a (4.mu zvzhq x1qppi91room where the temperature is $20 \; ^{\circ}C$. What is the fundamental
frequency if the pipe is open at both ends?

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61#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  The fundamental frequency in a pipe closewy-f 6hyik* n9d at one end is 330 Hz. What is the frequiw -6hykfy9*nency of the third harmonic?

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62#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  What is the length of the shortest pipe closed ,gbvt *u puq;veve,:2ha 9q0h on one end that will have a fundamental frequency of 60 Hz on vapqbq*vtu h2ehv g9;e :0,u,a day when the velocity of sound is 340 m/s?

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63#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A 3.00-m long pipe is in a x00c9) arm. din3smj nroom where the temperature is $20 \; ^{\circ}C$. What is the fundamental frequency if the pipe is closed at one end?

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64#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A 3.00-m long pipe is in a room where the temperature is ;4 /gb;*igr nnnht)s (vxp3lo $20 \; ^{\circ}C$. What is the frequency of the second harmonic if the pipe is closed at one end?

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65#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A closed organ pipe of length 0qi idb-0c9xj x (7:fk- fgs*qb.75 m is played when the speed of sound in air is 340 m/s. What is the fundamental frequencx:9 dg0(-k qc*i7 ffb q-bijxsy?

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66#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Consider two pipes of the same length: one is open and the other is clos7 d)q/b2p nu 0hnk* dmyst( w6d/;lsueed on one end. If the fundamental frequency of the open pipe is 300 Hz, what is the fundamental frequency of the closed pip0d/ phl 6ndqe yn*bm;) sd/t(k2 uusw7e?

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67#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Two adjacent sources each emhoq22,ugp ibuq-07de it a frequency of 800 Hz in air where the velocity of sound is 340 m/s. How much farther back would source 1 d2ih2,q7- bpo0 gue uqhave to be moved so an observer in front of the sources would hear no sound?

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68#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Two speakers are placed side by side and dtwidirshp ;8)fgg7; 9riven by the same frequency of 500 Hz. If the distance from a person to one speaker is 5.00 m and the person detects little or no sound, which of the following is a possible the distance from the person to the other speaker? s g;fg9tr8phi;wdi7 ) (The sound speed is 340 m/s.)

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69#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Two tunes have frequencies of 44+e 9bp lvb52z1rco4fqj (zsww 909opn0 Hz and 444 Hz. What is the beat frequency?

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70#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A music tuner uses a 52qvi* cm : 3s0h8t6fdmkbbapi4/ug8l 50-Hz tuning fork to tune the frequency of a musical instrument. If the tuner hears a beat frequency of 2 Hz, what8 q28t0hg m mcpba/uv4ii6dsb *kl :f3 is the frequency of the instrument?

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71#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  The wavelengths of the sounds produced by two horns are 6 m mc 19v+hjuk nti*g-i,and 7 m respectively. What beat frequency is heard when the horns are sounded on a day when tc,i i* h1unt+-9kmvjghe velocity of sound is 340 m/s?

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72#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  The corresponding violin strings on two violins in an orchestra aree8 ip0rc7 po5q found to produce a beat frequency of 2 Hz when a frequency of 660 Hz is played. What percentage change in the tension of8 orpce p57iq0 one of the strings would bring them to the same frequency?

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73#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  An observer approaches a statioebr x1tprlaw 3u.82 4xnary 1000-Hz sound source at twice the speed of soun 8 2 .rlp3tuer1b4waxxd. The observer hears a frequency of

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74#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A sound source (normal frequency of 1000 Hz) approa 7cfu1ps0y:d dches a stationary observer at one-half the spfs0d:d u c17pyeed of sound. The observer hears a frequency of

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75#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A sound has a frequency of 1000 Hz. If a listenedjqyfer,2zp6h6*7zrd.e (y 2br x tj9 r moves with a speed of 30 m/s away from the source, what is the frequenczrfryx. 2qt2y*hzj67 r6ed de( ,p9jby heard by the observer? (The sound speed is 340 m/s.)

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76#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A police car has an 800-Hz siren. It is traveling at 35 m/s on f:qdija2e / + v 9gfou(lrf59xa day when the speed of sound thf:9(jfe9u+i/gl2a fq5o drx vrough air is 340 m/s. The car approaches and passes an observer who is standing along the roadside. What change of frequency does the observer hear?

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77#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  What is the frequency heard by a stationary observer when a train approaches rqyd(1em kv5fae ,9dtx 6(z-p with a speed of 30 m/s. The frequency of the train horn is 600 Hzx(p 1 vkrete5a9 my-z6 f(qdd, and the speed of sound is 340 m/s.

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78#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A train is traveling toward you at 120 km/h. The train b)f.p)5 diiyil lows its 400-Hz whistle. Take the speed of sound to be i)5pd)i.f yli 340 m/s. What frequency do you hear?

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79#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  You are moving at 120 km/h toward a stationary train. The train bgylqq 9slu p)(fu 4d ,-ljz((rzwl(7 flows its 400-Hz whistle. Take the speed of sound to be 340 m/s. What frequency do you huull(z wq,q)4d(9r fpl(glyf- 7jzs (ear?

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80#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A train is traveling away( p dxb.2/lyyeh(t cgj+i28ol from you at 120 km/h. The train blows its 400-Hz whistle. Take the speed of sound to be 340 m/s.y2ilob(t8d gp+x/yehj .lc 2 ( What frequency do you hear?

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81#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A train is traveling away from you at 120 km/h. It blows its whistle, andx7 ai9,+ lfcd 3ohjwv* you hear a tone of 400 Hz. Take the speed ooj,dli+*73f 9axhwvc f sound to be 340 m/s. What is the actual frequency of the whistle?

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82#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  The frequency of a train h oo ;qo1(wkb6cvmqp.a2 2sa/ vorn is 500 Hz. Assume the speed of sound in air is 340 m/s. What is the frequency heard by an observer if tho a(6bosv2ac/mo w;q2pv q.k1e observer is moving away from the train with a speed of 30.0 m/s?

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83#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  The frequency of a train 9hcv e8gfr ow fan)*hl,;0 u,ihorn is 500 Hz. Assume the speed of sound in air is 340 m/s. What is the frequency heard by lreaniuh0 ,f9wg) ,hf ; v*8ocan observer if the observer is approaching the train with a speed of 30.0 m/s?

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84#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Sonar is used to determine the speed of an object. A 40-kHz signal is sent out,p4fnm+n g; 3ygm;7y gd and a 42-kHz signal is regpmgnfm+n;yd;4g3y7 turned. Assume the speed of sound is 345 m/s. How fast is the object moving?

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85#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  The half angle of the conical shock wave producz cunm2og ;nm ts+/cu 0j)/ sdn*i.o1 s.ete-bed by a supersonic aircraft is $60^{\circ}$. What is the Mach number of the aircraft?

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86#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A jet flies at a speed of Mach 1.4. What is the half-angle of the conicgdq 00ing q/ y )im06gzdn31cxal shock wz6g/qmx g0 )0 1dgqdnniyci30ave formed?

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87#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  The Concord airplane flies from the United St;tun;5y7lk, m6ur we0c wcj :tates to Europe with a Mach number of 1.05 wherem6c:e turc7,u;5w kjyl0 t;nw the air temperature is $5.0 \; ^{\circ}C$. What is the speed of the plane?

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