Physics Unit12: Sound - 51fly国际课程 (51fly.win)

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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 false statemenq2) z) u:d)rworp8dtm t?

A. Sound waves are longitudinal pressure waves.

B. Sound can travel through a vacuum.

C. Light travels very much faster than sound.

D. The transverse waves on a vibrating string are different from sound waves.

E. "Pitch" (in music) and frequency have approximately the same meaning.

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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 thrcds1i,o(tp) um.5k.mr0l l e5vamm3 u ough

A. gases.

B. liquids.

C. solids.

D. a vacuum.

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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 steel5g8.l;3wlc2 ak j fypr rod?

A. 1500 m/s

B. 3000 m/s

C. 5000 m/s

D. 8000 m/s

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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 incr6p (.m2:yshq*u*1 fsz pn dxireases, what happens to the velocity of sound? (Assume that all other factn q:.( 1sxhpd*z py *ims2r6fuors remain constant.)

A. It increases.

B. It decreases.

C. It does not change.

D. It increases when atmospheric pressure is high and decreases when the pressure is low.

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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 v52bylnrht8p / elocity of a 200 Hz sound through at yrh8/b l25npir is

A. twice as great.

B. the same.

C. one-half as great.

D. none of the above

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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 :bgtcqd ab-cx(w4 im0s 1(;vz Hz sound, the wavelength of a 200 Hz sound in air ibci4-bd1(( a c g; tqzxsm0:vws

A. twice as long.

B. the same.

C. one-half as long.

D. none of the above

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7#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Sound vibrations witxh 7z5cwo lox,5s n1/zh frequencies greater than 20,000 Hz are called

A. infrasonics.

B. ultrasonics.

C. supersonics.

D. none of the above

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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 2qnl+ g5- l9+isp3 9q wiyoyq-o0 Hz are called

A. infrasonics.

B. ultrasonics.

C. supersonics.

D. none of the above

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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 waves u,97a;bb2k opr8w9 mxwdcd, ylniformly in all directions. If you move to a point twice as far away from the source, the frequency of the sound lc 2pmd x9wb;8w,orbyk,da7 9will be

A. unchanged.

B. half as great.

C. one-fourth as great.

D. twice as great.

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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, intenmsuax: /x//dy 8(rfv-cjnr0nsity is proportional to

A. $R^2$

B. $R$

C. $1/R$

D. $1/R^2$

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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 sourceb7t mdp-v e:s6 at a distance d from the source is I. What is the intensity at a distance 2d from th67et-:mpsb dv e source?

A. $4 \; I$

B. $2 \; I$

C. $I/2$

D. $I/4$

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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 radiatinghr68k9)nzbzbi y)5 r b equally in all directions. What happens to the in6z5hr) 8bbk yi )bnz9rtensity of the sound? It reduces to

A. one-half its original value.

B. one-fourth its original value.

C. one-sixteenth its original value.

D. none of the above

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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 tzq f0,uzb.4fm2((: ta z,.yzud rs8zwn) zlxkhat is radiating equally in all directions. What happens to uy.,z0 wrnbz2us l. zfx)m(d48faz qk(t:z,z the intensity level of the sound? It drops by

A. 2 dB

B. 3 dB

C. 6 dB

D. 8 dB

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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 incre8y 3xhwyfp lz/8w/ a*vases as 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 chtrsojxtxea7ke7 0.ik 9 t9.+garacteristic of the souxet+797 to texik9g.ja0 k. srnd increases?

A. frequency

B. amplitude

C. wavelength

D. period

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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 / -se .vasef(sa musical note?

A. frequency

B. velocity

C. phase

D. amplitude

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17#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

What determines the "pitch" of a, 0jyy- be,fv7dhokybn(v k;/z t:ias -h14tb musical note?

A. amplitude

B. wavelength

C. frequency

D. phase

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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 1g.wcp83 lox nfqezd/ jp6/:e water

A. its wavelength does not change.

B. its frequency does not change.

C. its velocity does not change.

D. all of the above

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19#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Pressure and displacement wav)-qxjdy+8 bl 2is;wmw es are

A. in phase.

B. $45^{\circ}$ out of phase.

C. $90^{\circ}$ out of phase.

D. $180^{\circ}$ out of phase.

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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 ond1k+ c(aoup.qe/ oy* e a guitar string and the sound wave generated by the guitar as a result of *ke+/u yoecd.qa(1opthis vibration. What do these two waves have in common?

A. They have the same wavelength.

B. They have the same velocity.

C. They have the same frequency.

D. More than one of the above is true.

E. None of the above is true.

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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 wh n5j tk.fng5gy1 z0to)ich is open at both ends, there

A. are displacement nodes at each end.

B. are displacement antinodes at each end.

C. is a displacement node at one end and a displacement antinode at the other end.

D. none of the above

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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. Whane7i*f-b jm9ct are the wavelengths of the three lowest t m- jfnb79ce*iones produced by this pipe?

A. 4L, 2L, L

B. 2L, L, L/2

C. 2L, L, 2L/3

D. 4L, 4L/3, 4L/5

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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 pikphr.p-e;d2j60m+9t l-e 5foij k ncipe of length L is 200 Hz. Which one of the following frequencies will not r6+-92fjohmr0t.kn-c ;pk5ejd lpiie esonate in the same pipe?

A. $400 \; Hz$

B. $600 \; Hz$

C. $800 \; Hz$

D. $900 \; Hz$

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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 frequenc/7/ihz8 coi4u r+l, k/r bykaq6ao:bby. Which statement irkbl/uc+hkq 4:7izayab 8ibo,6 or/ /s correct?

A. The wavelength is 2L and there is a displacement node at the pipe's midpoint.

B. The wavelength is 2L and there is a displacement antinode at the pipe's midpoint.

C. The wavelength is L and there is a displacement node at the pipe's midpoint.

D. The wavelength is L and there is a displacement antinode at the pipe's midpoint.

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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 whi z b h;z+43,cnnwb7fmqch is open at one end and closed at the other, there

A. are displacement nodes at each end.

B. are displacement antinodes at each end.

C. is a displacement node at the open end and a displacement antinode at the closed end.

D. is a displacement node at the closed end and a displacement antinode at the open end.

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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 9ei n21ox cnzfgcr192 L. What are the wavelengths of the three lowest tonr2 1 oz219cenfg9icn xes produced by this pipe?

A. 4L, 2L, L

B. 2L, L, L/2

C. 2L, L, 2L/3

D. 4L, 4L/3, 4L/5

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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 closedb r+(bc /q0 z nlvp8o95ievbr8 pipe of length L is 200 Hz. Which of the following frequencies will not resonate in that pipe?r8z 0c 5n8b9qop(+vevrbi b /l

A. $400 \; Hz$

B. $600 \; Hz$

C. $1000 \; Hz$

D. $1400 \; Hz$

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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 closedwl;9ty . lve:vd7t*dm at one end is resonating at its fundamental frequency. W7:w lyd;.tl9t vdv*e mhich statement is correct?

A. The wavelength is 4L and there is a displacement node at the pipe's open end.

B. The wavelength is 4L and there is a displacement antinode at the pipe's open end.

C. The wavelength is L and there is a displacement node at the pipe's open end.

D. The wavelength is L and there is a displacement antinode at the pipe's open end.

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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. Eawnm8l.,a smz8 dofv) 55 1uyscch speaker produces a tone with a frequency of 200 Hz on a day when the speed of sou o8a1mm)yl8fuwn5s.,czs v d 5nd 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?

A. constructive

B. destructive

C. both constructive and destructive

D. neither constructive nor destructive

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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 beat2a fx,qge*nb /s, the two sound waves should have

A. the same amplitude.

B. slightly different amplitudes.

C. the same frequency.

D. slightly different frequencies.

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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 hea -qv(dfbb8d ko1 m2t()2tpnk nrd. Wha 1t()tobbk-(qpk2n 8vd2mdnft happens to the beat frequency if the frequency of one of the tones is increased?

A. It increases.

B. It decreases.

C. It does not change.

D. It could either increase or decrease.

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32#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

The Doppler shift explangb8to uke+) 9s6cb . 0/krnicins

A. why the siren on a police car changes its pitch as it races past us.

B. why a sound grows quieter as we move away from the source.

C. how sonar works.

D. the phenomenon of beats.

E. why it is that our hearing is best near 3000 Hz.

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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 hearz nr81vmod se/*t/ut1ca7n (zd by the observe zs7 zvnmtoae1ncdt u( *1r/8/r is

A. higher than the source.

B. lower than the source.

C. the same as that of the source.

D. equal to zero.

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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. The frequency heard byqk+*i:; -njh6xnnbj 81w cpib6wmj,s the obseqc ihn:j, j1nsbm+ * nw6 -w8p;bkjxi6rver is

A. higher than the source.

B. lower than the source.

C. the same as that of the source.

D. equal to zero.

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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-spema;i 9aq/hyh 1ed, its half-angle will decrease by a factor hqi ;hm/aa19y of:

A. 1/2

B. 2

C. $\sin^{-1} (1/2)$

D. none of the above

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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 in air is 352 m/s. Wxnbhap+7qm2g9 axdxrwe) m 6r0b.i;2hat is the air temperaturepxid0hm79rg .62r;aqxb mwbn + e2)xa?

A. $33 \; ^{\circ}C$

B. $34 \; ^{\circ}C$

C. $35 \; ^{\circ}C$

D. $36 \; ^{\circ}C$

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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 s+6t r5qp dwrq*peed of sound in air at $0 \; ^{\circ}C$ to the speed at $100 \; ^{\circ}C$?

A. 0.75

B. 0.85

C. 0.95

D. 1.1

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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 is 340 m/s, a bwd virr:r5q4 1at emits a shriek whose echo reaches it 0.0250 s later. How far away was the object that reflected rv i5w 41d:rqrback the sound?

A. $4.25 \; m$

B. $8.50 \; m$

C. $0.425 \; m$

D. $0.850 \; m$

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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. The tewky-4- rh2zcemperature is $0 \; ^{\circ}C$. How far away is the cliff?

A. $662 \; m$

B. $680 \; m$

C. $1320 \; m$

D. $1760 \; m$

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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 afte r:cw7/x 5japf.d,fcv r seeing a flash of lightning, the distance to the lightning strike isp.ccjf7x:dr5/fa w ,v about

A. 600 m

B. 1200 m

C. 1700 m

D. 2200 m

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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 o1yrs k6v - aldddd0m26n a day the temperature is $15 \; ^{\circ}C$. Approximately how far is the cliff from the observer?

A. $85 \; m$

B. $170 \; m$

C. $340 \; m$

D. $680 \; m$

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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?

A. $0.10 \; km$

B. $0.75 \; km$

C. $1.2 \; km$

D. $1.5 \; km$

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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 th we sr*f;quw83ui/3 epe splash 2.5 s later. How deep is the well? (Ignore air resistance, and assume twr/wu 33siepu q8;fe*he velocity of sound is 340 m/s.)

A. $25 \; m$

B. $27 \; m$

C. $29 \; m$

D. $31 \; m$

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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 frequ):y 3wcbgl++n* tk2 qul8enbdency 500 Hz is

A. 0.69 m

B. 0.75 m

C. 1.5 m

D. 1.8 m

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45#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Sound traveling in a;n1e5y dq6d..wh ko mair at $23 \; ^{\circ}C$ 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.

A. 0.230 m, 0.221 m

B. 0.221 m, 0.230 m

C. 0.321 m, 0.254 m

D. 0.254 m, 0.321 m

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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 intensim6 f*;on o,zpf(qmt ajyu+*5fty $10^{-3} \; W/m^{2}$?

A. $30 \; dB$

B. $60 \; dB$

C. $90 \; dB$

D. $96 \; dB$

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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 7-e1 s5a rzcddnzc;w0 ;8l g+uo0-dB sound?

A. $10^{-4} \; W/m^{2}$

B. $10^{-5} \; W/m^{2}$

C. $10^{-6} \; W/m^{2}$

D. $10^{-7} \; W/m^{2}$

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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 soun c:)p1em7vrvohjih2 p .)y;veds with intensity levels of 70 dB and 40 dB?e evi yvh1)v:2 7ohmr.ppjc);

A. 10:1

B. 100:1

C. 1000:1

D. 10,000:1

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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 is 100 dB. Wrtl+b) b2 q tg(d qlu5z2i;to1hat is the intensity level generated by one engine?tzq2o(b) qbtri l2ld; 5+ut g1

A. $67 \; dB$

B. $13 \; dB$

C. $44 \; dB$

D. $88 \; dB$

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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 j4djy ms bvz;,q y7o-+a source that is radiating equally in all direction ,jj-v7z; syqmdy o+4bs is
$6.0 \times 10^{-10} \; W/m^{2}$. What is the power emitted by the source?

A. $2.1 \times 10^{-8} \; W$

B. $2.7 \times 10^{-7} \; W$

C. $2.1 \times 10^{-6} \; W$

D. $2.7 \times 10^{-5} \; W$

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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 d5j9s -x*x+ejwu d2evof 6.0 m from a source that is radiating equally in all directions isd5x9j+e w -*v2xeju sd
$6.0 \times 10^{-10} \; W/m^{2}$. What is the intensity level in dB?

A. $18 \; dB$

B. $23 \; dB$

C. $28 \; dB$

D. $32 \; dB$

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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 uniformly8gk , ,pvrtajw,a1:nt distributed itv, :pa1, jrknawg,8 tn all directions. What is the intensity level at a distance 5.00 m from the dog?

A. $61 \; dB$

B. $63 \; dB$

C. $65 \; dB$

D. $68 \; dB$

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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 50n,2n )hnnkqs; ;9t nq7gqctn .00 m from a barking dog. What would be the intensity levnq n;ct0gst,)2hnn n k7 ;q9nqel if two identical dogs very close to each other are barking?

A. $65 \; dB$

B. $68 \; dB$

C. $130 \; dB$

D. $136 \; dB$

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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 w/h1 sl7u1vn (7d ymwpfrom 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 radiates nl w7/11ymdsp hv(wu7equally in all directions.

A. $55.7 \; dB$

B. $57.5 \; dB$

C. $75.5 \; dB$

D. $77.5 \; dB$

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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 dB. yr kv/89qjwz c )so,ojee0b(;At what distance wil)e swcy zb;joq ,re9/(jvko80 l it be 75 dB?

A. $25 \; m$

B. $50 \; m$

C. $75 \; m$

D. $225 \; m$

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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. Wha8do amf+)bb8.ihl -)notzp1 it is the fren+h)ib-a8.t)i z b1odfm8polquency of the fourth harmonic?

A. $400 \; Hz$

B. $900 \; Hz$

C. $1600 \; Hz$

D. $4800 \; Hz$

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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 )c boxgf-uxf8643q7kscuw ndf -q,u7 an open pipe is 900 Hz. What is the length of thfcu74x sgw ux 3b7c)ou-f -k6,8qdqnfe pipe?

A. $0.189 \; m$

B. $0.283 \; m$

C. $0.567 \; m$

D. $1.13 \; m$

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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 is 400 Hz. What is the hv6me0yp4 i kun7 (1rgwl.3uk8xyxl, frequ3 wm61ip7x,uk 4nx.(e8vl 0hrk yylguency of the lowest tone that will resonate in an open pipe of length 2L?

A. $800 \; Hz$

B. $200 \; Hz$

C. $1600 \; Hz$

D. $100 \; Hz$

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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 leng;7+d6bxqu adhsdd;sw2 7bla:th of 0.80 m. If the velocity of sound in air s +bsu xqal72addhwbd;:7;6 d is 340 m/s, what is the frequency of the second harmonic?

A. $213 \; Hz$

B. $425 \; Hz$

C. $638 \; Hz$

D. $850 \; Hz$

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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 where the0r+4 fwp) ov kg xk*mhv8;fid( temperature is $20 \; ^{\circ}C$. What is the fundamental
frequency if the pipe is open at both ends?

A. $57 \; Hz$

B. $114 \; Hz$

C. $29 \; Hz$

D. none of the above

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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 f ) pjmk-rgj5)pipe closed at one end is 330 Hz. What is the frequency ofr5f)j-k)m j pg the third harmonic?

A. $110 \; Hz$

B. $220 \; Hz$

C. $660 \; Hz$

D. $990 \; Hz$

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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 on one end t 4+*esypov1x 0bl9jxwhat will have a fundamental frequency o9p0x vyjsl *b+4w xeo1f 60 Hz on a day when the velocity of sound is 340 m/s?

A. $1.24 \; m$

B. $1.42 \; m$

C. $2.14 \; m$

D. $4.12 \; m$

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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 zep hors 2:vu*s s0uk9klqv:sg(r -.-room where the temperature is $20 \; ^{\circ}C$. What is the fundamental frequency if the pipe is closed at one end?

A. $57 \; Hz$

B. $114 \; Hz$

C. $29 \; Hz$

D. none of the above

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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 rlsaq;1uo)p e+ oom where the temperature is $20 \; ^{\circ}C$. What is the frequency of the second harmonic if the pipe is closed at one end?

A. $57 \; Hz$

B. $114 \; Hz$

C. $29 \; Hz$

D. none of the above

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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 s87wsh+(vlcy7o k iomzz8wd l27ikv(b1a jj14peed of sound in air is 34yd s2iokko ll4 1vv 8zc( i(hzwmjjw+8b7a7 170 m/s. What is the fundamental frequency?

A. $57 \; Hz$

B. $113 \; Hz$

C. $170 \; Hz$

D. $227 \; Hz$

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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:sorl4;ph:a,1u- lx f k one is open and the other is closed on one end. If the fundamental frequency of the open pipe is 300 Hz, what is the fundamental frequency of the closed pipe l,sp-k4rxo 1l:h;auf ?

A. $150 \; Hz$

B. $300 \; Hz$

C. $450 \; Hz$

D. $600 \; Hz$

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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 emit a frequency of ea 1y6-vu7*p h)qxjl k800 Hz in air where the velocity of sound is 340 m/s. How much farther bkhpx -uv7)j*ye ql a61ack would source 1 have to be moved so an observer in front of the sources would hear no sound?

A. $0.123 \; m$

B. $0.321 \; m$

C. $0.213 \; m$

D. $0.312 \; m$

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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 driveni,*msdm h4g0;bxda j; by the same frequency of 500 Hz. If the distance from a persd gx j4d,ab;i; mhsm0*on 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? (The sound speed is 340 m/s.)

A. $7.7 \; m$

B. $8.1 \; m$

C. $8.4 \; m$

D. $9.1 \; m$

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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 anmnfj :cr mu-cw*.1wh-d 444 Hz. What is the beat frequency?

A. $4 \; Hz$

B. $442 \; Hz$

C. $884 \; Hz$

D. none of the above

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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 ew8qc ooo jox4192+ih 550-Hz tuning fork to tune the frequency of a musical instrument. If the tuner hears a beat frequency of 2 Hz, what is the freqoweq4i+2ho9ooj 1x 8cuency of the instrument?

A. It must be 552 Hz.

B. It must be 548 Hz.

C. It could be either 552 Hz or 548 Hz.

D. It is neither 552 Hz or 548 Hz.

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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 bwl: jm qh0faj8r,hk9. y two horns are 6 m and 7 m respectively. What beat frequency is heard when the horns aqhwlajf h 0.98m: ,kjrre sounded on a day when the velocity of sound is 340 m/s?

A. $5 \; Hz$

B. $6 \; Hz$

C. $7 \; Hz$

D. $8 \; Hz$

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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 ;3bqbae4 u+ttmljd)7 on two violins in an orchestra are found to produce a beat frequency of 2 Hz when a freq t;b3mj t 7ae+)qludb4uency of 660 Hz is played. What percentage change in the tension of one of the strings would bring them to the same frequency?

A. 0.2%

B. 0.4%

C. 0.6%

D. 0.8%

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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 stationary 1000-Hz sound source *yvvni(fz6 k,* abtk68gbof8 at twice the speed of sound. The observer hears a freq,f v86b6a vifkb*z( 8 kn*tygouency of

A. 4000 Hz.

B. 2000 Hz.

C. 500 Hz.

D. none of the above

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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) approaches a statuthewvv el:rnx(*-aw u:4 z;,ionary observer at one-half the speed of sound. The obserwthu n,-uvzw;:xr4e le( :av*ver hears a frequency of

A. 2000 Hz.

B. 500 Hz.

C. 1500 Hz.

D. none of the above

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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 lw8kpl7rp q,k 3lo:u5 sistener moves with a speed of 30 m/s away from the source, what is the frequency heardrw8l suk37 ,qppok5 :l by the observer? (The sound speed is 340 m/s.)

A. $912 \; Hz$

B. $919 \; Hz$

C. $1000 \; Hz$

D. $1090 \; Hz$

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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 3575oz cdhp8vlh*k b.9 h m/s on a day when the speed of sound through air is 340 m/s. The car approaches and passes an observer who is standinvzcbh.57 p8*9 dholkh g along the roadside. What change of frequency does the observer hear?

A. zero

B. $82 \; HZ$

C. $166 \; Hz$

D. $249 \; Hz$

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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 observegp38ajldd0 p7ah/h s )r when a train approaches with a speed of 30 m/s. The frequency of the train horn is 600 Hz and the speed 07 )lsdhp8 djh/a 3apgof sound is 340 m/s.

A. $551 \; Hz$

B. $600 \; Hz$

C. $653 \; Hz$

D. $658 \; Hz$

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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 blows its 400-Hz wy:ozompdq 3 x g(xy(5*histle. Take the speed of sound to be 340 m/s. What frequency do you heaox:gqz m xyy5o3p *((dr?

A. $444 \; Hz$

B. $439 \; Hz$

C. $364 \; Hz$

D. $361 \; Hz$

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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 ;so nd .0s1n/qz-avob4f/st+w-h noqtrain. The train blows its 400-Hz whistle. Take the speed of sound to be 340 m/s. What frequefv;osq-d qoshost /4nbn-0n /z +.wa1 ncy do you hear?

A. $444 \; Hz$

B. $439 \; Hz$

C. $364 \; Hz$

D. $361 \; Hz$

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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 ce 0 n5. lhclhcyq:*p1train blows its 400-Hz whistle. Take the speed of sound to be 340 m/s. What fl:y.lnpc 1ccq h*0e5hrequency do you hear?

A. $444 \; Hz$

B. $439 \; Hz$

C. $364 \; Hz$

D. $361 \; Hz$

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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 whist.)x6jn+0 xl+cn biojn le, and you hear a tone of 400 Hz. Take the speed of sound to bexnn ij06) +cbxon+jl. 340 m/s. What is the actual frequency of the whistle?

A. $444 \; Hz$

B. $439 \; Hz$

C. $364 \; Hz$

D. $361 \; Hz$

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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. Assumesyfb64g vt0a. the speed of sound in air is 340 m/s. What is the frequency heard by an observs v04ygft 6.baer if the observer is moving away from the train with a speed of 30.0 m/s?

A. $500 \; Hz$

B. $456 \; Hz$

C. $548 \; Hz$

D. none of the above

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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 speed of souf lz k5t1s,6wq sdvp+h;/gxx .nd in air is 340 m/s. What is the frequency heard by an observer if the observer is approaching the train w1vdhwz,/ 5.sqt6k+;p xsgxl fith a speed of 30.0 m/s?

A. $456 \; Hz$

B. $500 \; Hz$

C. $544 \; Hz$

D. none of the above

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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 q/x /)mbh: vjsbawfj4p69 u)vspeed of an object. A 40-kHz signal is sent out, and a 42-kHz signal is returned. Assume the speed of sound is 345 m/s. How fast i9vs)v / quba4h jpmb6j /:xwf)s the object moving?

A. 6.9 m/s

B. 8.4 m/s

C. 331 m/s

D. 347 m/s

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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 co3 3zfvlt:r/ rnnical shock wave produced by a supersonic aircraft is $60^{\circ}$. What is the Mach number of the aircraft?

A. 0.87

B. 1.2

C. 1.7

D. 2.0

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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 thep26xct1)+f q.mo9i l8o fw cbi conical shock wave formedtmxp l2fi qw.+i 8c1 o69fo)bc?

A. $30^{\circ}$

B. $36^{\circ}$

C. $44^{\circ}$

D. $46^{\circ}$

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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 States to Europe with a M yhcpijl; n-a4ql- ,;lach number of 1.05 j -ql ;-i4lh,l;cyn pawhere the air temperature is $5.0 \; ^{\circ}C$. What is the speed of the plane?

A. 334 m/s

B. 337 m/s

C. 351 m/s

D. 359 m/s

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