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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://autodiscover.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://autodiscover.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 followi:y/ukxvnis7 67 4 ouizng is a false 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 conducted fastest thho w(1kk8 txqmz) 1nef0 rra18rough

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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 sted+3ye tgta: g(el 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 the air increases, what happens to the +vrl:a s8o azxf5 ;am4velocity of sound? (A xaa8v;+4lr:fa 5oszmssume that all other factors remain constant.)

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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 p449f iuka -95resdfy400 Hz sound, the velocity of a 200 Hz sound through air is49u a-9firpe45fsydk

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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 400 H9l: 7.eizny0h27 ivvamgp: yxz sound, the wavelength of a 200 Hz sound inihxy7y :0i:9 7pl 2me.nzv gva 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 greater t, ij.m8s q9fdghan 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 th -l6sx5ypmr ,9rhq1b.palss .an 20 Hz are called

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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 emid+xw zb9:dlr+wwe .(ytting waves uniformly in all directions. If you move to a point twice as far away from the source, the frequency of the soun bd(wer :x.zy+w+l9wdd 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, intensity is proporhvzo 3c/tw( g4tional 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 point source at a distancecggcc0er :c- 0 d from the source is I. What is the intensity ac:ccg r00gec-t a distance 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 mtbxua) (a rrn/3k)z, murj9p8a)8ocradiating equally in all directions. What happens to the intensit8za3r8b,pcmrmkunrj (o9ax )a)) /t uy of the sound? 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 is radiatie/ 8ch5 c +wt6tl4scqcpqo ymq*b.m8*ng equally in all direm e toc48+y6hqcc8qc *slqtmw5/ p .b*ctions. What happens to the intensity level of the 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 as a sound becomes l( x3un evm 7rhtwoylow2.00z4 ouder?

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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 characteristic v1f+i xb4pax( of the souxp x i+4a(vbf1nd increases?

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16#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  What determines "loudness" of a muslvf4x7mu ;2oei 00ioq ical 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 "pitmc,lkc(sf2 , tch" 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 intotjd; x2byo- :b water

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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* 16zzgo5z xf3szv)a q are

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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 guitar string and the sound wave generl4;rleg *m/98j 03ijk;/o pvs e 7xh sbmp.lemated by the guitar as a result of this vibrati /vs *bkil;; xjep.e7j 983hm0r4 /mlopsl gemon. What do these two waves have in common?

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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 both endsfj + xz;3vifr), 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. What are the wavelengths of the thrwaw+,6ak,eh5v 4dhs, eyd2 ybee lowest tones produceh,ekyda4sd 5+w ,y,vbw62ae hd by this pipe?

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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 inikk/fz. uw.:;m64b c-afkepn an open pipe of length L is 200 Hz. Which one of the following frequencies will not resonate in the sameb.an:zk kfc/u.; f pkw-e4i6m 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 res dgw b*c;o+8 qr2le9yc+.6a5vnqhbz aonating at its fundamental frequency. Which statement is correqy he.d29z 5gbw*+ 6n;v c8lbro+qacact?

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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 t3l 4hwk;p( rlp)8ymus he 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 length L. What ar w9()1)u ds(nyg;tzxkq zlv6 ce the wavelengths of the three lowest tones produced by this pipc k);t(g6()u 9dl1 qwznvzyxse?

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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 resonaotx tc:u 7w,)a+doo )ute in a closed pipe of length L is 200 Hz. Which of the following frequencies will nu7 ,t daxou)oto cw)+:ot resonate in that pipe?

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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 resonating at its fundamtas z2a,:1q37 n5sxx-hnd b rp(xb-ykental frequency. Which zpq 7y x,:n- ha-ak5s(3btdr bn21sxxstatement is correct?

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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 thznx 4aqavu p r3 ggwlr+jhxh/)*c:.x 0o 7a(6re same source. Each speaker produces a tone with a frequency of 200 Hz on a day whec p.g* x() nralhh:xr34r /70azgqo +au6xjvwn 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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30#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  In order to produce beats, tv0 6hcti3y.sk2 iq)wrhe two sound 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 sounded together and a particular beat frequency is heard. Wnk6xs) 1 udiamt9womc+v1(-dhat happens to the beat frequency if thvdnac1 mo+itm-w 6kx9s( du)1e 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 expl 8eu8y oqkrb)/0bzjt -ains

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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 frequzo 0cgs(fe0g( *ezl3y6o01fhwx 9e w bency heard by the observeo0 we1x6w(3yl b ezc0 oe9z*gh(s ff0gr 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 a stationary observer. T g bwa6pvb 4 pp75+o dhlf1qyx.xk5)p6he frequency heard by the oba.vw5p b6)o5qxx4 pgplpyk6+7d bh1fserver 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, itsbp6o sk3ny o1tqc,dv s7q5z ( btc1i+;mx5u. g half-angle will decrease by a factoqbpkt+q5s 5 ;g1(nc3dymzuv6oi,s txc1. o7br of:

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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 ultrasonic sound of frequency 45 kHz injqf:bn q fa5s q0u/,6y air is 352 m/s. What is the af6 qj/a0yfbqsn5u :,q ir temperature?

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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 tqjcu, ,ux,qk7s/cy++v .w wcbhe speed of sound in air at $0 \; ^{\circ}C$ to the speed at $100 \; ^{\circ}C$?

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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 in air isa65(kjnn* w y*lx,i.d2.v veat :fdtm 340 m/s, a bat emits a shriek whose echo reaches it 0.0250 s la( .m vjnwt i5ddla2 eta.:*y*v6,nkfxter. How far away was the object that reflected 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. Tnxiow vi5/j hbl.6 z;6he 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 a flash of lightning, t*5nkg zs1rp3x,n h/b-h+ slec he distance to the lightnin/n pnrkhcg,hsl -+*5se31b zxg 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.r3 anx/ qhihr ef(q:t3)p5* es)zfre temperature is $15 \; ^{\circ}C$. 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 later.-7vz+ ub* gflx How deep is the well? (Ignore fu + -b*l7xgvzair 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 sound wave of frecgm,m ) s fwym2xs+9u+g;ib4vquency 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 r y.i36si9sg hw+ ma5hg)wl *gat $23 \; ^{\circ}C$ 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 t ef7fn q*c x)h lxr2fb9id197w(7mttsound with intensity $10^{-3} \; W/m^{2}$?

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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 obab 0 jfx3 a 3bjzlie2yzg917*f a 70-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 soune:ny; ov2gwr8--bxif et 7p(fds with intensity levels of 70 dB and 40 oie -e8p f2rgv(w;7nxf -bty: 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 garage.cc+v ru3zrnbl7 a*qmq 281 tw is 100 dB. What is the intensity level genera r.qcuvtb3r 7wq l*82cnaz+1 mted by 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 source that is rkzwwyzc9j7-9md p:q: adiating equally in all direct:7- 9w9yqzz jk dc:mpwions 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 m fb.9an* 6ne 5vyhyl4j srom a source that is radiating equally in all direction9*nlny6asb.4 5vyj eh s 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, whichu0(ft *te y*ww is assumed to be uniformly distributed in all directions. What is the intensity level at a distance 5.00 m fr y (ufetwt*0w*om 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 froe zrjd:9rr 1h je+a.1xm a barking dog. What would be the intensity level if two identical dogs very close to each ot .heja+ejrd: 119xr zrher 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 m from a sound source the intensity leve ua,)+uic 3o2 vu8)-z+yxd rfxikfo1 rl is 60 dB. What is the intensity level (in dB) at a point 2.0 m from the source? Assume that the source radiates equally in 2uu+ yok rxrix) ido1c8ff)vzu3a,+- 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 lev.cy)7*p/uf1coacwf 4ll yk j: el 5.0 m from a point source is 95 dB. At what distance will it be c a ulfl:.c )7y4c opkf*1jw/y75 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 frequ1q 9 l5wbu yeul(ops y i7e*/xcx:y+k1ency of 1200 Hz. What is the frequency ofycpu9ob *( ei5lqkew11s +xuy/ 7yxl: the fourth 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 of an open pipe is 900 Hz.l7o 0pga12mvv What is the length of the pipe?va2 7ovlmg0p1

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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,fa8z upo;/ v9wn)4ffkwemhg:i /y;p in an open pipe of length L is 400 Hz. What is the frequency of the lowest tonv,)pg;e/wafhn8 op mizy /4 uw 9ffk:;e 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 both ends has a length o;k7p ;trtm,7c /xr idgwxuz11/sqh 2 ef 0.80 m. If the velocity of sound in air is 340 m/s, what is the r/u7r tpix1mkh2s;w1 c7xe d;qgtz ,/frequency of the second 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 room wh,+ zvj mtvh)g8ere 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 closed at one end is wv md y7w.5e-m330 Hz. What is the frequency of the third h-vd.7w 5y wemmarmonic?

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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 toadcdh/a():sj 6o8:/ eu l ztihe shortest pipe closed on one end that will have a fundamental frequencl/cj/( z :u)o6 :i8 esdhtdoaay of 60 Hz on 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 ro .af3oopt6 1cblt 5mg:om 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 igvkn 7 w5:sx(xs $20 \; ^{\circ}C$. 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 0.75 m is played when the speed of sound 4vi:3t w qgurdwxan.. uy++ ukd6s)v)in air is 340 m/s.u.qd)r k snw)d4 a6vgu:t +vw3x+ u.yi What is the fundamental frequency?

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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 cq-j 8-inet8 hxlosed on one end. If the fundamental frequency of the open pipe is 300 Hz, wha-8njxq- eh8i tt is the fundamental frequency of the closed pipe?

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67#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Two adjacent sources fns0+ xny8 aj1hc7 k/deach emit a frequency of 800 Hz in air where the velocity of sound is 340 m/s. How much farther back would source 1 have to be moved so an observer in fh/js n18dxkf7 0a+n ycront 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 driven by the e x8obpi+x/( nsame frequency of 500 Hz. If the distance from a person to one speaker is 5./nox+i( ebpx800 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? (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 440 Hz and 444 Hpj0pwo8d 3y+ftmd+jwv -1j8 a z. 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 550-Hz tuninyax h(gm-8lhb1ftc /8zm2 9gdg fork to tune the frequency of a musical instrument. If the tunerymhtx g/gba flm8cz 2(1hd89- hears a beat frequency of 2 Hz, what 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 and 7 m respectivawy ot/o2d0 w*ely. What beat frequency is heard when the horns are sounded on a day when the velocity of sound is 340 / wtdoyw*20o am/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 o-8 (i 8xo+vpencb2 aiarchestra are found to produce a beat frequency of 2 Hz when a frequency of 660 Hz is playe- 82on+a i( vpxb8iaced. What percentage change in the tension of 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 aj66 pm p)76lt0i fvj;im(,/ox7qur9 npiac a u stationary 1000-Hz sound source at twice the speed of so pan6uco7amjiimqjtr/ up70ix6 9;lp,f )6v(und. 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 fak;m.qf g(e oq, s 0v9zo k4dd-n ;ybb.-kne,Hz) approaches a stationary observer at one-half the speed of sound. The observer hears a fqz.vf ( , k .nobm gy-ksq-d4,0n ;feok9ead;brequency 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 listener moves p7ulxpp*o3*gwith a speed of 30 m/s away from 3l*gx7o*p pup the source, what is the frequency 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 sa2-45 w2iksl 0,kqb4jgff. 9 ijvxphsiren. It is traveling at 35 m/s on a day when the speed of sound through air is 340 m/s. The car approaches and passes an observer who20f jjvw l2fbip, ga.kh 9-sq5ix4sk4 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 approach4ds. .pcw s2w 3zgylqbm* + 1xik:ynv/es with a speed of 30 m/s. The frequency of the train horn is 600 Hz andg *24ns:+vi .1.pwcx/dz wl3 ybkqsym 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 t ic7l9bh*xo.sxx/cks5,uo 4b c: bp 9xrain blows its 400-Hz whistle. Take the speed of soun5lsobsh/*coxc ,9xx.pk c94 b7:bxu id to be 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 t0s m dbtx vx3mid:r8bm:jc;9:wim/, erain blows its 400-Hz whistle. Take the speed of sound to be 34vm,/ s:x:dc;8d30i bm:m9ex ti mbrj w0 m/s. What frequency do you hear?

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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 from you at 120 km/h. The train blows ij-od*ys. 8eb)i 0lq5: 5sjxuqoo maj1 ts 400-Hz whistle. Take jlso:oj1 ix)s *-5bd8j yoqqu .0 e5amthe speed of sound to be 340 m/s. 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 8uhz gv,83uy p.qtld ;0qy( xoat 120 km/h. It blows its whistle, and you hear a tone of 400 Hz. Take the speed ofyu .d;h88,3gt (vpzl x qou0qy 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 horn is 500 Hz. Assume the speed of sound in air is 340( /q/ ptuzls,sek +t5b m/s. What is the frequency heard by an observer if the obser5p, ku(/s lqbe+/ ttzsver 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 horn is 500 Hz. Assume the spee4wl4g -l,thq. b pmo)ed of sound in air is 340 m/s. What is the frequency heard by an observer if the observer is approaching the train with a speed of 304 e .mlht4,wlqbp)g -o.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 outkm v2+uov: /y;t3rgj lsnwr( 3, and a 42-kHz signal is returned. Assume the speed of sound is 345 m/s. How+ :jvrr3o wk3tlm gu/v2; (nys 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 wav5.tlrs6y ; 9hajk2qj ze produced 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-angleksuu-rs:f ),e of the conical shock wave u,ss:ufrk )-e 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 d)rjh9a( agu:States to Europe with a Mach number of 1.05 w:h9 ja)r(udga here the air temperature is $5.0 \; ^{\circ}C$. What is the speed of the plane?

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