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 iks ;w.k.ol ,vhi-tb8 p6zyer;s a false statement?

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 fasrn kkm1 .o;os6xzz)l-test through

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 k n7f2 kn66sqnsound in a steel 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 thxf9 n7/gbypt2 ; wykr1a/y rt)e air increases, what happens to the velocity of sound? pty2y )x/;/ga1k7y 9 brwntr f(Assume that all other factors 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 sdz v*weyf n0f86ok :)kound, the velocity of a 200 Hz sound throug*)fk fzv6deo80:n wkyh air 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 Hz sound, the 1p vx) ghd*3g2ztcyz* wavelength of a 200 Hz sound in airx*y )3gtz dh2pczv 1*g is

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 with frequencies greater than s;rvrr7* uqh;*6 imvaj8dn/ c20,000 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 20 Hz are callcvs wjv4kpl*:ic 5)2 zed

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 emittingcz gxvs*8z0t5 waves uniformly in all directions. If you move to a point twice as far awag80v* xc5zstz y from the source, the frequency of the sound will 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 wavesbt z9q fd;m-3dt ug:27f)lvl nc4fi8e, intensity 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 source at a distance dm( 5qzqkn r4 w 3 vj -nqc5l(g0wbpqzu-m87(ss from the source is I. What is the intenskbp 4 scjn5 wq0(qmznu-lg8smrq7q (z5w -v(3ity at a distance 2d from the 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 radiating equak,a0lg ,wz7 ,y 6tcfpolly in all directions. What happens to the intensi, y7two,az kc6l 0pf,gty 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 that iso(kooqosn- lj 33x70j radiating equally in all directions. What happens to the i qxk7j(j33 n0o ools-ontensity 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 increases as; gp*ism9my f) 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 chau4xndzj )+pq 0racteristic of the sound increaseq0jnx)+up 4z ds?

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 "louj2 h s42dr ofh4gljn1-dness" of a 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 musicl-4jofh) 2 htaal 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 in zeb 39p- ue3nw3r+razto 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 waves8u d)4l+iv+rom)/k znte2v np 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 on a guitar s285stg7 ep wdh4sz4 1l,jvtsg2iaas1tring and the sound wave generated by the guitar as a result of this vibration. What do these two waves 84jtd5zeaast7s h2is,wvg12 gp41s lhave 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 which is open af1dq cfp)g az8 isch: +b*c)m:t 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 *k-me d5 cqof2length L. What are the wavelengths of the three lowest tones -oc em 25fkq*dproduced 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 pipe of5fnhy+u4+ 7usf 2ggnk length L is 200 Hz. Which one of the following frequencu4sg5+n+fhyk fg72u nies will not resonate 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 frequency. ( dam6 r4:ux7zw8pc ph Which statemen( pudr:a4hm7 8pczwx6t is 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 which iss.x8bo ju(enm*m 2xr cl *((iy 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 L. What are the wavelentbdun3y 55a,idm3 0imj; smz.gths of the three lowest tones produced by this pipe?3i3m;.damji 05,nzbm du yst 5

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 closed pipe of length L is 200 Hzw*gq 4uiiu f1uhzo* 6k /m3pg*b;ws;c . Which of the following frequencies will not resonate i/ ;ugk z6bf*su q*i1 w4m*o3 ;wcipughn that pipe?

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 clog ,pji wybb+e ;rgb3zsc93+6hsed at one end is resonating at its fundamental frequency. Which sta+gjrwb zby ,9 3+pes3i6;gb hctement 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 saec2 14ymb *.llwfzt57c nin-fme source. Each speaker produces a tone with a frequency of 200 Hz onl cyc54- . ln*mew27 ftibz1fn a day when the speed of sound is 330 m/s. The person is
1.65 m from one speaker and 4.95 m from the other. What type of interference does the person sense?

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 beats, th x7qm*ldgp h;2e 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 heard. )+ xel hds3 () ws22yfpdtyfn,What happens to the beat frequency if the frequency of one of the tones)y+ely)t p f x23sfdsw 2(,dnh 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 expi d k99)hcdm(gftco 8(p mc6gw6ln,9alains

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 sy8zb3 z8k 3jrqtationary observer. The frequency heard by the observeryzbjkz8 3 3r8q 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 by thf,o9**7y cd 0svenxcpe observ07 9o,ncpfd *cesyxv*er 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-speed, its half-angle will decrea i(5 p*;cazvuqse by a icpzu (v;*qa5 factor 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. What i ifb,7rgu/ cfl: h,8c ,9ctqpos the air tempelfg,cqr /,c,f9pco 7thb:iu8rature?

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 sps+d l9a04ksjn eed 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 i x7wcjeycg*j.n/ ,0km/s, a bat emits a shriek whose echo reaches it 0.0250 s later. How far away was the object that reflected back the soun/0wc, y.kge7cj n x*jid?

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 temperatured h m7 v.jz;j5em76s*x5sdfk q 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 5fu/+ t1q nb8mz.0 s after seeing a flash of lightning, the distance to the lib+tzf/8 muqn1ghtning strike is 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 (c:-hs /lnzuvsrs5gcb5v t,p ) qp6*d a cliff on 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 healx08/ jezb+hjr the splash 2.5 s later. How deep is the well? (Ignore air resi0j/zhbjel +8xstance, and assume the 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 frequency 500 Hu8d i+ kwj5 ,(v9vqomtz 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 air at 0 i;ut mrg;j*v$23 \; ^{\circ}C$ 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 souzp jqldy1uq7h*hv6n-dt;; 0/q eh)b nnd with intensity $10^{-3} \; W/m^{2}$?

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 intensitnom5578rd7m 2asj bemy of a 70-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 inten72lz8 kbp;3-utod :2je ,gdj dyf yrt3sities of two sounds with intensity levels of 70 dd jf lu b;d37e-rogdy2jzy ,82tkp 3:tB and 40 dB?

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. What is the intensdot+nqvma, qc(1e . x.ity level generated by one engv, mctn o.+dx.qaeq1(ine?

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 a sourcxx0 2yq+8tp7gm: dbh-sjcq 1 ie that is radiating equally in -xpb7g 1m 2y +8js:ch0 qitqxdall directions 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 of 6.0 m from a source th9o .i( w+cthtsat is radiating equally in all directiocot( sh.+i9tw ns is
$6.0 \times 10^{-10} \; W/m^{2}$. 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, )uhk3kfb 4z o:which is assumed to be uniformly distributed in all directions. What is the 4h): 3bfuzk kointensity 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 5.00 m from a barking dog. What wos,nr eed;+ ,l3)q4uezliw 6 bjoc*.utuld be the intensity level if twoz.ol;+rqebu u,6 dlj)4i ew,cen3*ts 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 from a sound source tp1w5;z7xdfg yun9 uc5q.ioo) he intensity level is 60 dB. What is the intensity level (in dB) at a point 2.0 m from the source? Assume that the c o7x;wuiy5dg5).fq9nzpo 1 u source radiates equally 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. At what distancecb*7tln/g m fq)g)+ic will it be 75 dBgg/*7f c) lmtcn+ib) q?

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. What l5v5x caarm g3*3cp1rt izr-2k h)n6 cis the frequency1 t 35na rxl5rv cch-m*2a3rz)pik gc6 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 an open pipe is 900 Hz.rf2yu o/(7s;p+jx 8 hoch 6kic What is the length of the ;u2op8(s7+xjr yc o/h6cf ikhpipe?

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 resona3u rvd3/ u 9/d+yekvwjte in an open pipe of length L is 400 Hz. What is the frequency of the lowest tone that will ujeur/d +3dkv/ w 9y3vresonate 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 lengt9z si+xzee3*uh of 0.80 m. If the velocity of soundi*+zuse zex 39 in air 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 the teeblj+sruq n+2cbub(3 2. 73qcmq3 ez vmperature 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 pipe close7vsej:s (uji d7j5wp7d at one end is 330 Hz. What is the frequency of t577s(: jdjpisvej u 7whe 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 that will have osv5s/f(,7wr ht.taua fundamental frequency of 60 Hz on a day when the velocity of sound is 340 m/s7u(rsa. w5 vs ttf/o,h?

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 room rir8mi bf hlt 2he,-*oj65n*twhere 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 room wh )pol7vdfi7 l-7; ghgbere 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 speed of sound in vc0zdv65vay.:j ,ixu) k1e je0;joe lair is 340 m/s. What is the fundamental fe., :e6azj ekoyj;xu i50v)cjd0lv 1 vrequency?

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 lengtmi.et 6x wq20 xj -agr.b/9gdyh: one is open and the other is closed on one end. If the fundamental frequency of the open iq.gb a9yxg6.tejm 2rxw-0 /d pipe is 300 Hz, what is the fundamental frequency of the closed pipe?

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 800 Hz in air where the velocity oeza7;js ju31 m4raq 8l+ ajj)cf sound is 340 m/s. How much farther back would source 1 have to be moved so an observer in front of the sources would j 3ujsajr4qml+; eja)a 7cz81hear 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 driven by the saq : 3/iyp1hvbt3wwj o;me frequency of 500 Hz. If the distance from a person to one speaker is 5.00 m and the person detects little or no sound, which of thio1j /yp3bqwv:3tw h;e 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 oft5pl*kd rj.7-ihiep * 440 Hz and 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 550-Hz tuning fork to tune the frequency of a musical instzu*i:i. he4 3knyu w9r7b.iqsrument. Iir3 h9zn7k*wuyb:.eiis 4q .uf the tuner hears a beat frequency of 2 Hz, what is the frequency 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 by two horns are 6 m and 7 m rn- nq.mylsbv0px rq 3q f1-)z6espectively. What beat frequency is heard when the horns are sounded on a n. 0xlsqbm6f1ryzq- n-q vp3)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 on two violins in aq): k0 t;yu 3k 5rmb2fuddtum6n orchestra are found to produce a beat frequency of 2 Hz when a frequency of 660 Hz is played. What percentage change in the tenskmdft;q3 u b5 utdy026) murk:ion 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 104 onl(rztb* ;dgzm e-tz8: h.r00-Hz sound source at twice the speed of sound. The obs- lz.d4;ntm(hrrz:8be* gzto erver hears a frequency 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) approachea0*rwn33a z tr*gnal7s a stationary observer at one-ha zwatnn**3r 0a 7lar3glf the speed of sound. The observer 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 k gzlr, *+m;qvHz. If a listener moves with a speed of 30 m/s aw*rkq+mg zv,; lay from the source, what is the frequency heard 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-fh;3*w.n ff ksHz siren. It is traveling at 35 m/s on a day when the speed of sound 3;nfff h*s .kwthrough air is 340 m/s. The car approaches and passes an observer who is standing along the roadside. What change of frequency does the observer hear?

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 observer when a tqt(v9y2zqm9f 3g3k,wr( p eonrain approaches with a speed of 30 m/s. The frequency of the e t 2q9k9 gvnryz3owp,(qf3m( train horn is 600 Hz and the speed of 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 ybj *z, heg xvli5r4i2+ou at 120 km/h. The train blows its 400-Hz whistle. Take the speed of sound to be 340 m/s. Whatzv 2,g+*xbi 5ih4l jer frequency do you hear?

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 totk /-nm3az9/ g4zvz.d ttmjjny.7 9aqward a stationary train. The train blows its 400-Hz whistle. Take the speed of sound to be 340 mtz-4nd/ tzt/mv yqamk jn 9ga.j.739z/s. What frequency 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 n;sae fn ;oa-1zrpxpuql8+7fwq:h ; -120 km/h. The train blows its 400-Hz whistle. Take the sp7;elxn- :a1q f+ f-hnu;sap;pzq8wr o eed of sound to be 340 m/s. What frequency 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 awu .5rnn 1 pk,mum;pcd/ay from you at 120 km/h. It blows its whistle, and you hear a tone of 400 Hz. Take the speed of sound to be 340 m/s. What is the actual frequency /dpnmr. ukun,;5c1 pmof 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. Assume the speed of sound in air is 4bx 4 pnusa3kb;a2 tw(ib4mg8 340 m/s. What is the frequency heard by an observer ifx4amba3bwp;gk28t4ib (uns 4 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 sp+wf*/2tubn ae eed of sound in air is 340 bfu wat+ /ne*2m/s. What is the frequency heard by an observer if the observer is approaching the train with 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 speed of an obju. a8tc04yblsws/ v+rect. A 40-kHz signal is sent out, and a +ssw/ t.4bl 0yc8rvua42-kHz signal is returned. Assume the speed of sound is 345 m/s. How fast is 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 conica5z :xm4 waum0a3bc. ril 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 haa1:g -m5pgopyj 86rlhe+f vs2m jxs*-lf-angle of the conical shock wav- faoe5j*-ys6:p8vgms+xpj2 l h rm 1ge formed?

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 Stateo/;tt0lzdrz64 *hw zhs to Europe with a Mach number of 1.05 where tr4;ht *l6zo0z hwz/d 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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