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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 so n-44pyx zxel7t +c;k ,xjzko3und travels as a wave?
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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 pva yqwq*xq- t87t7/p energy?
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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 homin,w ; w0z3ocnrx6q5 3juc m /t(u.pchemade “telephone” by attaching a string to the bottoms of two paper cups. When the string is stretched and 3onc,uqpxt; /c mw3n0r.6wzh5( jicua child speaks into one cup, the sound can be heard at the other cup (Fig. 12–29). Explain clearly 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 a)s7fi 82a7ge 2utx1 wwhwp e7air into water, do you expect the frequency or wavelenw wa 1gthw7ea8fxe7p72i2 u s)gth 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 on59t -kw qualjl1 9.lnf sound in air does not depend significantnk.ul-n9l 1jql9aw5t ly on frequency?
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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 heliu+wn mjwjuku/ *o/7hw/m 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 vu*,d79lhr (id2ntamk48v e sof organ 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 reducmj3t-2u2z2d (g obie hpr6gv1e the amplitude of sounds in2 1u3ghr- 2zbd(m6pigo v2ejt various frequency ranges. (An example 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 together0:fq 2 ge3k dob/hh5uqwn/m8p as you move up the fingerboard toward tb0/8 mn h5 hgq of3:ue/kq2wpdhe 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 approac8w z,02ekdz/gexa;z * p0 fltn5bjwr :hes you from behind a building. Initially you hear it but cannot see it. When it emerges and you do see it, its sound is suddenly “brighter” — you hear more of the highrk05pgj*e;,dtb:ew xznzl 0 8a2 w/fz-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 saie.tn8// *4 j rdqrsloup, gm3md to be due to “interference in space,” whereas beats can be said to sdoupg/83 4rqj r emlm *nt/,.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 of the speakers weag)+ zoyqeu3x(mf7x7 5b6x6 a7bu ogcre lowered, would the points D and C (where destructive and conx 6x)oue fg g(z77+yu36mc aboba5xq7 structive 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 protectt:+d4cbt d ;ncing the hearing of people 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 ambient noise. Instead, a;t4n:dt+cbd c 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– qm*;5zxr8xij l; - 5obgch.b n:ipds931. Each wave can be thought of as a superposition of two sound waves with slightly different frequencies micdog *sb9:pxn ;5lhx r.z- jq8i5b;, 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 observer moz4 ly1nqzw5lg+k5g0cve in the same direction, with the same velocity? Explaikwg4q1 ygz0zc 5+l5 lnn.
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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 th6n) kg1g(/s,qztwkc 5 uby pk7e frequency of the sound heard by a person at rest with respect to the source? Is the wavelength or velocity chang b)( 1y/ 7z,nkkqgksu6 wgpct5ed?
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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 position:1bbds vm,.dv s of a child in motion on a swing. A monitor is blowing a whistle in front of the child on the ground. At which position, A through E, wi v.1bddmv:s,bll 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 lengt1lr;acndg7eg yf 4p: g)qr-5im/)kz xh of a lake by listening for the echo of her shout reflected by a cliff at the far end of the lake. She hears the echo 2.0 s after shouting. Estimate the length of tgg dga- )rf1yqe/z)x ;5ck74 l:rpimnhe 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 ship just below the waterline. Hetls6 pu g*.rn: hears the echo of the sound reflected from the ocean floor directn slg.:r6pu*tly 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 significantly 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 wavel+ )z*o,ze txvp 3,jariengths in 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 ety0z-/zy+y s r/ lja)drifting just above a school of tuna on a foggy day. Without warning, an engine backfire occurs on z+rje a - )ys0lt/yz/yanother boat 1.0 km away (Fig. 12–33). How much 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 topjzv c:*7u oc0yk)s surcpul9l:p0 *:j of a cliff. The splash it makes when striking the water below is heard 3.5 s later. How high is the cliffckjj u)l:op7*lvy:z r*9c sp0: ucsu0 ?    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 ground, sees a huge stone strike the conc*lgts el2z3ipgtyv4u*b+s9 teju +27 rete pavement. A moment later two sounds are heard from the impact: one travels in the air and the other ite+l pvtgsg*7y *3z ul u+ s9j4tb2i2en 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-second rule7i usm ;nl/xx 9gbf0g/” for 0 g9fs7; ulxbmnxg//iestimating the distance from a lightning strike if the temperature 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 pain levs 7fplny(w;x,6ez 9n3x 6 rc,akaod)c el 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: e+rx((ipnpwphf f3e.py6 v9 $2 \times10^{ -6}W/m^2$?    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 when fired simultaneousd ain ye1munz*1h +,s+ly at a certain place, what will be the sound level if only one is expl+m+ s in1nzae,y *u1dhoded? [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 from an airplane with four equa; vrw w2q/v+enlly noisy jet engines is experiencing a sound level bordering on pain, 120 dB. What sound level would this person experience if the captain shut d+2vevww/;n rq own 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 to have a signal-to-noise ratio of 58 lf0xx +s ,tpx*dB, whereas for a CD player it+p x* tlx0x,sf is 95 dB. What is the ratio of intensities of the 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 output of sound fsv//h*n2q59iy c vnl(+ oomogrom a person speaking in normal conversation. Use Table 1(ov ov9y/ ic*sn/+ nmh lqg5o22–2. Assume the sound spreads roughly uniformly over a sphere centered on the mouth. $\approx$    $ \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 strikes an eardrum whose area il8y/p,jhz2z w pat vufp.g( (3s $5 \times10^{ -5} m^2$ (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 rated at 250 W, ft /b5y*xgeoj56smv-*6w xlgwhile 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 from abt* y f exl5o/*6mg-swj x6vg5 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 dB when placed 2.8 m in g. nq -j )wgq2alsvo,4front of a loudspeaker on the staglawq-svjonqg) .g4 ,2e.
(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 typicx5z x6q, m1sdce5 dk)7ufvcrhl-e8,p ally detect a difference in sound level of 2.0 dB. What is the ratio of the amplitudes of two sounds whose),uhrz 71xcxe6pfs 8dd-ec mkv l,q55 levels differ by this amount? [Hint: See 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, (a) by what factor will t* m(xesyu d9n*he intensity incr yd xn9emu*(*sease? 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 displacemente +i: 4belxbcb ,wu*t2 amplitudes, but one has twice the frequenctiw2e:ex ub+lb,b c *4y of the other. What is the ratio of their 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 corresposu4eiem d ;z1w(/1rsg nds to a displacement amplitude of wu1 /dg(me;1isr4ez svibrating 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 havc;uhi+rvr 2mle;lp8 9e what sound level to seem as loud as a 100-Hz tone that has a 50-dB sound lep2 ; l9uvherir+mc8;lvel? (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 fr4- ezvceke *hob+9,nhc4ms; qequencies that an ear can detect when the sound level e;ksec, 9vcm44e q+b* hhnzo-is 30 dB? (See Fig. 12–6.)

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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 accocw uy68by4 tg1mmodate a huge range of sound levels. What is the ratio of highest to lo8tuw c4b6gyy 1west intensity 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 viocim (ft,fe-(o,6o 9jy f7 xhtzlin has a fundamental frequency of 440 Hz. The length of the vibrating portion is 32 cm, and it has a mass of 0.35 g. Under wha(yjo (mx- itcff,t fh79oze 6,t tension 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. What are 2g.7 hu3s pal(znxvx6the fundamental and first three audible overtones if the pipe( 3splxghzv.7ua 2xn6 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 -uaqep 2 98qz 3 hmbb(3elorq.5a6fnrwould you expect from blowing across the top of an empty soda bottle that is 18 cm deep, if you ab3(q-83fh.qu9 maezqpl5 on6 arr2eb ssumed 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 pipepaw1m,lx) xf j svj+j9m (v8n6 organ with open-tube pipes spanning the range of human hearing (20 Hz to 20 k)91s ( f,vj n6wmmjxa+vljp8xHz), what 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 540 Hz un3.)b+flzffvx x;hl6k r: y4as its third harmonic. What will be its fundamental freque+r63bh;fn)fx xylukl 4z: fv.ncy if it is fingered 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.b 8sgc;y7pql 973 m long and is tuned to play E above middle C (330 7lysgcq8;9bp Hz).
(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 that emits middle C (262 Hz) whenffyx 9*)ts51r 0s tcvk the temperature is 21 ff*c5x)vtytss91 0 rk$^{\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 20 gi)i 5;h,mk yk;cr)xorg sz 337i i9jj$^{\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 mouthpiece of the flute in Example 12–10 should the hole qjd y97o88f io hr12ifbe that must be uncovered to play D above middlo2 ifyi9 fdqohr 1887je 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 pipe can resonate at 264 Hz, 440 Hz,hw m7-)yz,d ozg+*3wtkl 7qc 8l1qbks and 616 Hz, but not at any other frequencies in between. (a) Show why this is an open or a closedw g7q qbhy3lzwd*l)m,z c1 t 8s7k-ok+ 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 1.80 m long isg rmw ,- -j7.yb:(hydknzsgx7 open at both ends. It resonates at two successive har7ydgbmgjzr7.:xh,n ( -s y- wkmonics of frequencies 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 e53ni5 ih:6s0 rdfax x2hq8ng$^{\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 within the audible range for a 2.14-m-long organlz,lrmj- *; xze 57gsn pipe ar7ml5xez*n,gsl-j ; z t 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. It is open to the/,,-krv-r*essp.-j amezs abey n30m 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 grakme/,-s, a r3vss pn-ejzm*b. -a0reyph 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 o.jk9w9 dkbac/l, fl2 pne beat every 2.0 s when trying to adjust two strings, one of which is sounding 440 Hz. How far ofb.pafc9dw/,29 lkljkf in frequency is 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 if middle C (2/wf,nz3nd1jd+y zjjx)n/a 8k62 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 23.92ui7 kmd lb/s5 kHz, 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 27 bisk ul/dm9played simultaneously, 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 9 /;e ) 5yq q *pbjqd6ahlsj5fz7beats/s when sounded with a 355-Hz tuning fork. What is the vibrational frequencyjdq5jq /lp7h6 y*);5q sfzae b of the 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 same frequency, 294 Hz. The tension in one u ei*sjei+j(iyok mda5 p.8.1string is then decreased by 2.0%. What will be the beat frequency heard when the two strings are played together? [Hint: Recall Eq. 11–13.]o uk jpy(8.ieme1i+*5aj si.d    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 twb4(sok k3k kx+o identical flutes each try to play middle C (262 Hz), but43kxskk bko +( one is at 5.0°C and the 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 Bk2jy9u5 3j(-ylmzwxjh *)gx afonb ,* has a frequency of 441 Hz; when A and B are sounded together, a beat frequency of 3 H9 b gj fju3x o,m*wzhl)j-5y(n*ykxa2z 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 apart. A person stands 3.00 m ea g:fzb+vg6 amd44p4 from one speaker and 3.50 m from the other. f azadgp+: e4bm64v4 g
(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 vi 2 28uzienwlvmh+lhs m2 -)z3lbrating at 132 Hz, but a piano tuner hears three beats every 2.0 s when they are played together. (a) If one is vibrating at 132 Hz, what must be the frequenzevnu8l2l s 2h mw-m3i)hl+2zcy 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 or o* h-i ztato;y*8mw(f wavelengths 2.64 m and 2.76 m in air. How many beats per second will be heard?* -t womor(i 8y*za;th (Assume T = 20 $^{\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 o1a6jvqs/hs iuf;b.txufm)(y- hv4 iw);7f wk f a certain fire engine’s siren is 1550 Hz when at rest. What frequenhw-fi)i s.bs7(u1 jf; tky ; v)fvw4qxumh/a6cy do you detect if you 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 lg s/b 3 w8)hj)*1goxgyuh6js0 odo,va fire engine whose siren emits at 1550 8*yo)wb1)3djo 6g us,gsx 0g/vojhh l 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 shiftazr4 atag9r5xssqo 14o , 8m9d in frequency if a 2000-Hz source is moving toward you at 15 m/s versus yoaq5ms,19 dt ar rzo4x8 s9g4oau moving toward it at 15 m/s Are the two frequencies exactly the same? Are 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 s7 k l7 sl,drabnk /0a*bnk*px-ame single frequency horn. When one is at rest and the other is moving toward the first at 15 m/s the driver at rest hears a beat frequency ofkpdslbkb,k*x *07 /7 a-lannr 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 receivet- tvox uf ) (e*xwh/:ur9c*rns them returned from an object moving directly away fromox( )ctu vhx:r-e 9n*rw/tuf* 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 al0rne39p )wrc speed of 5 m/s As it flies, the bat emits an ultrasonic sound wave with frequency 30.0 kHz. What frequency does the bat hear in the reflected wave? re nwc 0l9r)p3   $ \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 Doppler experiments, a tubaun -7 ygksdw55ewy86;x sbhe- was played on a moving flat train car at a frequency of 75 Hz, and a second identical tuba8w- - 56huxdg y;5s7ee kbyswn played the same tone while at rest in 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 t 5mi*c n3vffz3w-u.nfo measure blood-flow 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 expected beat frequency if blood is flowing in l .5cm3 nfif*u -3fvnzwarge 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 waves ofsw g/rvjdqu9s (4i5b* 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 emitc,(ldszv x qqpw413k/ t jwd6(s sound of frequency 570 Hz. When the wind velocity is 12 m/s from the north, what frequency will observers hear who are located, a/dsw(34(pv j qd16,wxqct lz kt 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 s5op hm.,fpkez 5d4)24wq-t vla)tof3:v dym land if its speed 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 i o1 aqe.et4m1vahrwbvmf 3v+ :ar)h20 s the angle rmr3 af:o+t )hq4h2ebv01w m1.avve athe shock wave makes 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 soun7 h 9tethax6r(d is only ab tta67h9e rx(hout 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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