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习题练习:SoundSoundSoundSound



 作者: 王信东Wood发布日期: 2025-01-19 20:51   总分: 78分  得分: _____________

答题人: 匿名未登录  开始时间: 01月19日 20:51  切换到: 整卷模式

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1#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
What is the evidence that sound travels as a waluq ))t;r-pk1dy f *scve?
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2#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
What is the evidence that sound is a form of enerxvwrkyn 0hni355o8:uhp8*v wgy?
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3#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
Children sometimes play with a homemade “telexo:2z 0mwytk+ phone” by attaching a string to the bottoms of two paper cups. When the string is stretched and a child speaks into one cup, the sound can be heard at the other cup (Fig. 12–29). Explain clwt m+2zk x0y:oearly how the sound wave travels from one cup to the other.
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4#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
When a sound wave passes from air into h)fik 9wa5+xzrpgam k) 8z5(fwater, do you expect the frequency or wavelen)za xfm fwr ()k+hkzg9ap5i8 5gth to change?
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5#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
What evidence can you give that the speed of sound in air does : d1 st(mhc*oenot depend significantly on freec:(*ts h1dom quency?
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6#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
The voice of a person who has inhaled hel5 *czdp5i ur3cium sounds very high-pitched. Why?
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7#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
How will the air temperature in a room affect the pitch of orgad;0lzxwriwlb rge2 ;2 b,pf31n pipes?
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8#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
Explain how a tube might be used as a filter to reduce the amplii/v3j: a7t dme j9,g3 nhk0gcktude of sounds in various frequency ranges. (An ei,j3d hk kgva:ne9gc03/mjt7 xample is a car muffler.)
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9#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
Why are the frets on a guitar (Fig. 12–30) spaced closer together as you move uf o3e ek6q,zv(p the f,o(kee 3 q6vfzingerboard toward the bridge?

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10#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
A noisy truck approaches yo-i so)4.og . a ,e,vtrffktt/dbl9d9vu from behind a building. Initially you hear it but cannot see it. When it emerges anlotab.ve tfrfdigsv, tk/ )d .-o, 499d you do see it, its sound is suddenly “brighter” — you hear more of the high-frequency noise. Explain. [Hint: See Section 11–15 on diffraction.]
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11#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
Standing waves can be said to- yy4fa*3fbeywc(nt 0 be due to “interference in space,” whereas beats can be s*ta0 bynyff c(wye4 -3aid to be due to “interference in time.” Explain.
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12#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
In Fig. 12–16, if the frequency o g+;b(ph ayib w+ n7r8ake78ckf the speakers were lowered, would the points D andkw 8pg7ynaa7+i 8(+kb; ebcrh C (where destructive and constructive interference occur) move farther apart or closer together?
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13#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
Traditional methods of protecting the hearing of people p tt11id4y-5ylwuop)emx y88,p.uvd who work in areas with very high noise levels have consisted mainly of efforts to block or reduce noise levels. With a relatively new technology, headphones are worn that do not block the ambientl-oie tx )8y.w8,pu4ut1vyd1myd p p5 noise. Instead, a device is used which detects the noise, inverts it electronically, then feeds it to the headphones in addition to the ambient noise. How could adding more noise reduce the sound levels reaching the ears?
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14#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
Consider the two waves shown in Fig. 12–31. rll;81 c 4no8; x4vkqcxirc.dEach wave can be thought of as a superposition of two sound waves with slightly different frequencxkol;dc rr8c18 4n4 q. ;vlicxies, as in Fig. 12–18. In which of the waves, (a) or (b), are the two component frequencies farther apart? Explain.
(12-31)
(12-18)
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15#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
Is there a Doppler shift if the source and observe;ywv3f a-g khd ,q7nt;r move in the same direction, with the same velocity? v k3q ftwg7n;;, ha-dyExplain.
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16#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
If a wind is blowing, will this alter the frequency (y 6,te rswe,jm3o (ioof the sound heard by a person at rest with respect to the source? Is the warmo, ey6sio etj(,3 w(velength or velocity changed?
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17#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
Figure 12–32 shows various positions of a child in motion on ff bgm )d6la9j3en;f :a swing. A monitor is blowing a whistl ;)ne :ff3 fljg96dabme in front of the child on the ground. At which position, A through E, will the child hear the highest frequency for the sound of the whistle? Explain your reasoning.

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18#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A hiker determines the length of a lake by listening for xf rva8sqc;o,v n.k3q-j 1cux5 td,/z the echo of her shout reflected by a c.;/ct rc3 k-q51,novz8 ,juasdxf qxv liff at the far end of the lake. She hears the echo 2.0 s after shouting. Estimate the length of the lake. $\approx$    $ \times10^{ 2}$m

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19#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A sailor strikes the side of his 8p p(+2i ht)l t(wiokvship just below the waterline. He hears the echo of the sound reflected from the ocean floor directly below 2.5 s later. How deep is the ocean at this point? Assume the speed of sound in seawater is 1560 m/s (Table 12–1) and does not vary significa o8h(lk i(pwvt+)2p itntly with depth.    $ \times10^{ 3}$m

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20#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  (a) Calculate the wavelengths i19 irerj gxk(ns2q4u(layck): )8fs xn air at 20 $^{\circ} $ C for sounds in the maximum range of human hearing, 20 Hz to 20,000 Hz. $\lambda_{20Hz}$ =    m $\lambda_{20kHz}$ =    $ \times10^{-2 }$ m(b) What is the wavelength of a 10-MHz ultrasonic wave?    $ \times10^{ -5}$m

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21#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  An ocean fishing boat is /vyk-rh :7fn+t1 y4py zkk8qhdrifting just above a school of tuna on a foggy day. Without warning, an engine backfire occurs on another boat 1.0 km away (Fig. 12–33). How /: +7th -kqk1vyfyhrk npy8z4much time elapses before the backfire is heard (a) by the fish,    s (b) by the fishermen?    s


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22#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A stone is dropped from the tb5 g cwelf y2nr94l,z8uqa4ez 9(pj:g op of a cliff. The splash it makes when striking the water below is heard 3qr(,9cugl4aw :8j5b lne4ye29z zf pg.5 s later. How high is the cliff?    m

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23#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A person, with his ear to the growv j f ):b8:ph r5kl6r6veysd;und, sees a huge stone strike the concrete pavement. A moment later two sounds are heard from the impact: one travels inbhlrfrv:py)vd5k; w js: 6e86 the air and the other in the concrete, and they are 1.1 s apart. How far away did the impact occur? See Table 12–1.$\approx$    $ \times10^{2 }$m

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24#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Calculate the percent error made over one mile of distance by the “5-secr/.b/gdxj, dm s8 6fe1 *kqgwbond rule” for estimating the distance from a lightning strike if the temperaturj./ *6 bx,1/e fgkdbs mgqd8rwe is (a) 30 $^{\circ} $ C, $\approx$    % (b) 10 $^{\circ} $ C$\approx$    %.

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25#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  What is the intensity of a sound at the nm+exy ;r5cw 2bqbs+cjtot*b;) x;u ; ,uo3 jcpain level of 120 dB?    W/$m^2$Compare it to that of a whisper at 20 dB.    $ \times10^{-10 }$W/$m^2$

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26#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  What is the sound level of a sound whose intensity is mm5xt4i1u(l+ s:shjj $2 \times10^{ -6}W/m^2$?    dB

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27#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  If two firecrackers produce a sound level of 95 dB xu4 lb0x/5/a+egb eppwhen fired simultaneously at a certain place, what will be the sound level i+bbe e0x4u5/a pglx/p f only one is exploded? [Hint: Add intensities, not dB’s.]    dB

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28#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A person standing a certain distance fromh.ms r5os cu.5 an airplane with four equally noisy jet engines is experiencing a sound level bordering .sh o5urcms.5 on pain, 120 dB. What sound level would this person experience if the captain shut down all but one engine? [Hint: Add intensities, not dB’s.]    dB

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29#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A cassette player is said wef )t /67u/xc80kb6ckhnwp d to have a signal-to-noise ratio of 58 dB, whereas for a CD player it is 95 dB. What is the ratio of intensities of the6ek bhwp wtdf 68/cxk/7)cn0u signal and the background noise for each device? 58 dB =    $ \times10^{ 5}$ dB =    $ \times10^{9 }$

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30#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  (a) Estimate the power oueky d+oa 4hmv2(d9x8ltput of sound from a person speaking in normal conversation. Use Table 12–2. Assume the sound spreads roughly uniformly over a sphere centered on the moutv +hky (le mdd298a4xoh. $\approx$    $ \times10^{ -6}$W(Round to the nearest integer)
(b) How many people would it take to produce a total sound output of 100 W of ordinary conversation? [Hint: Add intensities, not dB’s.]$\approx$    $ \times10^{7}$people

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31#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A 50-dB sound wave strikesj 6xf)c 3l()nyuwrvxj m3ap14 an eardrum whose area is $5 \times10^{ -5} m^2$ (a) How much energy is absorbed by the eardrum per second?    $ \times10^{-12}$W (b) At this rate, how long would it take your eardrum to receive a total energy of 1.0 J?   $ \times10^{ 3}$yr

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32#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Expensive amplifier A is ziwbssi *6 8f)rated at 250 W, while the more modest amplifier B is rated at 40 W. (a) Estimate the sound level in decibels you would expect at a point 3.5 m zbi*)8i 6 sfwsfrom a loudspeaker connected in turn to each amp.$I_{250}$ =    dB $I_{40}$ =    dB (b) Will the expensive amp sound twice as loud as the cheaper one?

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33#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  At a rock concert, a dB meter registered 130 djoso)i 2a.3/rnqjfu11puk w +afam2wf ))5sgB when placed 2.8 m in front of a loudspeaker on the/f . u3aajqifgw)wrn21omapfs2 ksu5 1 ) )j+o stage.
(a) What was the power output of the speaker, assuming uniform spherical spreading of the sound and neglecting absorption in the air?$\approx$    $ \times10^{2 }$W(“Round to one decimal place)
(b) How far away would the sound level be a somewhat reasonable 90 dB?   $ \times10^{2}$m

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34#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Human beings can typically detect a difference in sorabm 2-zri7w 0v o5-epund level of 2.0 dB. What is the ratio of the amplitudes of two sounds whose levels differ by this amount? [Hint: Seever r7 p-ozwb-ai5m20 Section 11–9.]$\approx$   

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35#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  If the amplitude of a sound wave is tripled, nqzpp i (p/6x-c-9gto;q ,bhv(a) by what factor will the intensity increaht o,/(g iz6vbn-;qpx qpp -9cse? Increase by a factor of    (b) By how many dB will the sound level increase?    dB

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36#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Two sound waves have equal displacement ah v1yp3cks+(exwvz c 5o)b t/)mplitudes, but one has twice the frequency of the other. What is the ratio of thei k5c+(3vsw xc1 yhb/oe t)pzv)r intensities?   

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37#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  What would be the sound level (in dB) of a sound wave in air that correspo0bjss0y 3m 7c+mcv;e pu(0ebonds to as30j uo+c70 vs0 pe;yebcm(mb displacement amplitude of vibrating air molecules of 0.13 mm at 300 Hz?    dB

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38#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A 6000-Hz tone must h .+ .blempe2nuave what sound level to seem as loud as a 100-Hz tone that has a 50-dp.eeub ln+ m.2B sound level? (See Fig. 12–6.)    dB


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39#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
What are the lowest and highest frequencies that an earqw 5fs 1r( 8qa*p8nzrv can detect when the sound level is 30 dB? (See Fig. 12v*awp 1nr (qz88s5frq–6.)

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40#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Your auditory system can accommodate a huge range of sound leveli+3 6ccgykzt12l e,u/xg u/x4b,h idx; h4zwks. What is the ratio of highest to lowest intensytc62 g,z/ ekg4i+bulxz 4;chw dku,i3hxx/1ity at
(a) 100 Hz,$ \times10^{ a }$ a =   
(b) 5000 Hz? $ \times10^{ a }$ a =   
(See Fig. 12–6.)



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41#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  The A string on a violin has a fundamental frequencb:t zb sakm:ev:,qqd f5 47v-ly of 440 Hz. The length of the vibrating portion is 32 cm, and it has a mass of 0.35 g. Under what te,:tqv am:ez:bl5-k4 bsvfd7q nsion must the string be placed?    N

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42#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  An organ pipe is 112 cm long. Walrht7+7md r3yuxvei0csx3 8 c5 wa2p2 0n r1hhat are the fundamental and first three audible overtones if t02h370chuvirrpl873x2mw 1 sc redtan5 xy+ ahe pipe is
(a) closed at one end, $f_{1}$ =    Hz $f_{3}$ =    Hz $f_{5}$ =    Hz $f_{7}$ =    Hz
(b) open at both ends?$f_{1}$ =    Hz $f_{2}$ =    Hz $f_{3}$ =    Hz $f_{4}$ =    Hz

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43#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  (a) What resonant frequency would you expect from b.b cxmi( bkn/9lowing across the top of an empty soda bottle that is 18 cm deep, if you /b.ibc9x(mkn assumed it was a closed tube?    Hz (b) How would that change if it was one-third full of soda?   Hz

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44#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  If you were to build a pipe or+ eqktom 0 c0gvs umg**maelow:(2m;de2 . *togan with open-tube pipes spanning the range of human hearing (20 Hz to 20 kHz), kmsl2 tm*;2.0a0 w eed*m t* (:+guvcooqgoemwhat would be the range of the lengths of pipes required? $L_{20 Hz}$ =    m $L_{20 kHz}$ =    $ \times10^{ -3}$m

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45#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A tight guitar string has a frequency of 54 (5q5rrd o6bcpkgr z 5 at+d4lq,a0gm.0 Hz as its third harmonic. What will be its fundamental frequency if it is fingered5gd55p6akzg( cbr.aq4 0l tmqr,+ rod at a length of only 60% of its original length?   Hz

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46#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  An unfingered guitar string is 0.73 m long and is tunedx .b58 lx :gjxmddu4z,edj(m ) to play E above middle C (330 Hz).dge8 x)4m : ld.xmx(,bzjjud5
(a) How far from the end of this string must the finger be placed to play A above middle C (440 Hz)?$\approx$    m
(b) What is the wavelength on the string of this 440-Hz wave? $\approx$    m
(c) What are the frequency and wavelength of the sound wave produced in air at 20°C by this fingered string?    Hz    m

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47#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  (a) Determine the length of an open organ pipe th2bw qfv2crgrx/ j)h7, ayi*f0 hix*6zat emits middle C (262 Hz) when the temperatu x*hxi2rf * j7ifq zr0ayb2c/h)g6vw,re is 21 $^{\circ} $ C.    m
(b) What are the wavelength and frequency of the fundamental standing wave in the tube?    Hz    m
(c) What are $\lambda$ and $f$in the traveling sound wave produced in the outside air?    Hz    m

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48#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  An organ is in tune at 29 kkkp(ef)gz r1cvvm44-: oj x0 $^{\circ} $ C. By what percent will the frequency be off at 5.0 $^{\circ} $ C?    %

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49#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  How far from the mouthpiec0/b(tva c8 rbee of the flute in Example 12–10 should the hole be that must be uncovered to play D above middlrb8cvt(0bae/ e C at 294 Hz?    m

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50#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  (a) At T = 20 $^{\circ} $C how long must an open organ pipe be to have a fundamental frequency of 294 Hz?    m
(b) If this pipe is filled with helium, what is its fundamental frequency?   Hz

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51#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A particular organ pi;s *svbvr t6/epe can resonate at 264 Hz, 440 Hz, and 616 Hz, but not at any other frequencies in between. (a) Show why b/svr est;*6v this is an open or a closed pipe.   (b) What is the fundamental frequency of this pipe?   Hz

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52#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A uniform narrow tube 1.887vlp be 0b98ymf3oxx0 m long is open at both ends. It resonates at two successive harmonics of frfvx0bxel o87 yb3m89 pequencies 275 Hz and 330 Hz. What is
(a) the fundamental frequency,    Hz
(b) the speed of sound in the gas in the tube?$\approx$    $ \times10^{2 }$ m/s

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53#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A pipe in air at 20 d su f- hy, 1c5sdx1eym7oh5bn6b nx-+$^{\circ} $ C is to be designed to produce two successive harmonics at 240 Hz and 280 Hz. How long must the pipe be, and is it open or closed?    f =    m

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54#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  How many overtones are present witxiu *qk.j,yl6hyav 3. hin the audible range for a 2.14-m-long organ pipe at .6vj3uy.ik,qhx al*y 20 $^{\circ} $ C
(a) if it is open,   
(b) if it is closed?   

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55#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  The human ear canal is approximately 2.5 cm long ssulac qb 7beu(2,3*y. It is open to the outside and is closed at the other end by the eardrum. Estimate the frequencies (in the audible range) of the standing waves in the ear canal. What is the relationship of your answer to the information in the graph 37 usbq ly,a(be*u2cs of Fig. 12–6? $f_1$ =    Hz $f_3$ =    Hz $f_5$ =    Hz


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56#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A piano tuner hears one beat every 2.0 s when trying to adjustx (i g l.cgo19/xbr(8afhb/c m two strings, one of which is sounding 440 Hz. How far off in frequency i1. b hi((/c9r8 a/cfomxbgxlgs the other string? ±    Hz

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57#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  What is the beat frequency* z* m utqwypmj8kx9)0 if middle C (262 Hz) and $C^#$ (277 Hz) are played together?    Hz What if each is played two octaves lower (each frequency reduced by a factor of 4)? $\approx$    Hz

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58#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A certain dog whistle operates at 23.5 kHz/rr qck/5veqwp. b)v7.b *ilh, while another (brand X) operates at an unknown frequency. If neither whistle can be heard by humans when played separately, but a shrill whine of frequency 5000 Hz occurs when they are played simultaneous7rk5w.)pcq l /qe/* .brbivvhly, estimate the operating frequency of brand X.    kHz

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59#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A guitar string produces 4 beats/s when sounded with a 350-Hz tuning fork and 5xhhhl3 dohk;t0oy,6 9 beats/s when sounded with a 355-Hz tuning fork. What is the vibrational frequency of thhhdo k;0o3xhl ,5tyh6 e string? Explain your reasoning.    Hz

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60#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Two violin strings are tuned to the s+ 6 5uwb.e-)ynyc;5hyoagd klame frequency, 294 Hz. The tension in one string is then decreased by 2.0%. What will be the beat frequency heard when the two strings are played together? [H) + 6lyh. o-g;ubdeawn5y5yc kint: Recall Eq. 11–13.]    Hz

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61#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  How many beats will be heard if two identical flutes each try to play middnp vmpvk2 21)hle C (262 Hz), but one is at 5.0°C and p1n 2 v)ph2mkvthe other at 25.0 $^{\circ} $ C?    beats/sec

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62#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  You have three tuning forks, A, B, and C. Fork B has a frequency of 441 Hz; wbn u, ns.ommx79/7y 3q7vjk bkhen A and B are sounded togethe y77 bvkuxsq9jko3b.mmn n ,/7r, a beat frequency of 3 Hz is heard. When B and C are sounded together, the beat frequency is 4 Hz. What are the possible frequencies of A and C? What beat frequencies are possible when A and C are sounded together?$f_A$ =    Hz or    Hz
$f_C$ =    Hz or    Hz
|$f_A$-$f_C$|    Hz or    Hz

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63#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Two loudspeakers are 1.80 m apip ;e hq9*xue-xtf8s +art. A person stands 3.00 m from one speaker and 3.50 m from th9fei xhup *;q8xest+-e other.
(a) What is the lowest frequency at which destructive interference will occur at this point? f =    Hz
(b) Calculate two other frequencies that also result in destructive interference at this point (give the next two highest). Let T = 20 $^{\circ} $C $\approx$    Hz $\approx$    Hz

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64#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Two piano strings are supposed to be vibrating at 132 Hz, but x-+1p se(v6jehhg h7. tfts,ua piano tuner hears three beats every 2.0 s when they are played together. (a) If one is vibrating at 132 Hz,6egux-tsh t1ejv,h+. ( h7 fsp what must be the frequency of the other ?   Hz    Hz
(b) By how much (in percent) must the tension be increased or decreased to bring them in tune?   % increase    %decrease

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65#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A source emits sound of wavelengths 2.64 m and 2.76 m in air. How many betruiblcw-1-v- . e0o alxg8o6 ats per second will be heard? (Assume T = 1a 6 eo8o- -0.l bgcxliw-utrv20 $^{\circ} $C)$\approx$    Hz(round to one decimal place)

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66#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  The predominant frequency of a certain fire engine’s siren is 1550hmhj2f ,5ooblc 2p( 2q Hz when at rest. What frequency do you detect if you22hoq( poj,blh2 f5c m move with a speed of 30 m/s
(a) toward the fire engine,    Hz
(b) away from it?   Hz

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67#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  You are standing still. What frequency do you detect if a fire engim vt28,op( xbune whose siren etub(2x 8pm v,omits at 1550 Hz moves at a speed of 32 m/s
(a) toward you,    Hz
(b) away from you?   Hz

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68#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  (a) Compare the shift in freq7 / xkl+ q6qw6fwaprh)uency if a 2000-Hz source is moving toward you at 15 m/s versus you moving toward it at 15 m/s Are the two frequencies exactly the same? 6x/p7aqlwr )+qf6hk wAre they close? $f'_{source\,movine}$    Hz
$f'_{observe\,movine}$    Hz
(b) Repeat the calculation for 150 m/s and then again
$f'_{source\,movine}$    $ \times10^{ 3}$Hz
$f'_{observer\,movine}$    $ \times10^{ 3}$Hz
(c) for 300 m/s What can you conclude about the asymmetry of the Doppler formulas?$f'_{source\,movine}$    $ \times10^{ 3}$Hz
$f'_{observer\,movine}$    $ \times10^{ 3}$Hz

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69#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Two automobiles are equipped with the same single frequency horn. When one is2ew nr1gjc)8z at rest and the other is moving toward the first at 15 m/s the driver at recz1gne r w)8j2st hears a beat frequency of 5.5 Hz. What is the frequency the horns emit? Assume T = 20 $^{\circ} $C    Hz

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70#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A bat at rest sends out ultrasonic sound waves at 50.0 kHz and receives them ret 38q)0uv hkitiurnhi3uk) 0vqit 8ed from an object moving directly away from it at 25 m/s What is the received sound frequency?    $ \times10^{ 4}$ Hz

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71#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A bat flies toward a wall at a spee9y3m2f .jgiq td of 5 m/s As it flies, the bat emits an ultrasonic sound wave with frequency 30.0 kHz. What frequency does the bygj23 tq 9i.mfat hear in the reflected wave?    $ \times10^{4}$ Hz

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72#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  In one of the original Doppl7zmdu6 3u, p f1;z,xv qjkglt9er experiments, a tuba was played on a moving flat train car at a frequency of 75 Hz, and a second identical tuba played the same tone while at rest ijp1 ,l6z3ftdkq9 mz;ux,uv7gn the railway station. What beat frequency was heard if the train car approached the station at a speed of 10 m/s ?   Hz

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73#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A Doppler flow meter uses ultrasound waves to measure blood-flow gjwqmhlnlr.+5z* 5h):xbrdi-s, i r0 speeds. Suppose the device emits sound at 3.5 MHz, and the speed of sound in human tissue is taken to be 1540 m/s What is the expectedm 0rwrzld+j*h5: ilnsih) .,rgxq-5b beat frequency if blood is flowing in large leg arteries at 2 cm/s directly away from the sound source?   Hz

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74#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  The Doppler effect using ultrasonic s7 oi457sy6z7sfza bq vh47qhwaves of frequency $2.25 \times10^{ 6}$Hz is used to monitor the heartbeat of a fetus. A (maximum) beat frequency of 500 Hz is observed. Assuming that the speed of sound in tissue is $1.54 \times10^{3 }$ m/s calculate the maximum velocity of the surface of the beating heart.    m/s

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75#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A factory whistle emits sound/u6uah* hjs4 s of frequency 570 Hz. When the wind velocity is 12 m/s from the north, what frequency will ob6u *uhashj4 /sservers hear who are located, at rest,
(a) due north,   Hz
(b) due south,   Hz
(c) due east,    Hz
(d) due west, of the whistle? What frequency is heard by a cyclist heading    Hz
(e) north    Hz
(f) west, toward the whistle at 15 m/s?   Hz
Assume T = 20 $^{\circ} $C

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76#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  How fast is an object moving on land if its speed9szim*i pd y;yf;u 8g5 at 20 $^{\circ} $C is Mach 0.33?    m/s
(b) A high-flying jet cruising at 3000 km/h displays a Mach number of 3.2 on a screen. What is the speed of sound at that altitude?    m/s

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77#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  An airplane travels at Mach 2.3 where the speed of sound is 310 m/s (a) What is55p-)w v6 eriwjj9krf the angle the shock wave mak9w -5 rpe5jvk6jwi f)res with the direction of the airplane’s motion?    $^{\circ} $
(b) If the plane is flying at a height of 7100 m, how long after it is directly overhead will a person on the ground hear the shock wave? $\approx$    s (Round to the nearest integer)

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78#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A space probe enters the thin atmosphere of a planet where the speed of sound uq0/wdr-jmfj,f0 r)gy3h (zliszwfyrl)0rm-gf u dqj3j, /0 (h only about 35 m/s
(a) What is the probe’s Mach number if its initial speed is 15000 km/h$\approx$    (Round to the nearest integer)
(b) What is the angle of the shock wave relative to the direction of motion?    $^{\circ} $

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