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 ishse9 6v1q+ xrvwmbfo 5-sk2.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 fastest throug*)bnfkj:/u ys;2e,dt o p9 vffh

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 soyeprnr i ;8+w,jy5s-bad tha3ug90 ,lund 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 the air increases, what hap)-v +fp ufq fyp3vou;8a2 j3k .ufs;dipens to the velocity of sound? (Assume that all other ;82s- p3qv;k of)jya.ipfudffuu3+ v 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 sound, the velocity of a 2j0fi y: ;cr4 45ovfouk00 Hz sound through air i vyiuj koc:0 454roff;s

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, txly1ui42 my6fd:g 2e/t*bifzhe wavelength of a 200 Hz sound in air isbi:2d/g 2f*u zilef6 ymy14tx

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 20,000 Hz are can5.1vxmxt (g:c+6pz sqr* xh jlled

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 a 6qrqy01eu*a+ +pmgg nre 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 unifor pg kjib-;/j,qmly in all directions. If you move to a point twice as far away pj,/;q b -ikgjfrom 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 waves, intensity is proportionals,r0 p3gp87gwxif).l av 3tkp 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 al9c bhtjv, , jlk4fh37 distance d from the source is I. What is the intensity att l3fbk , 4hvchj7,9jl 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 r vw(;r+nl0pt vadiating equally in all directi tr+vnl w;p(0vons. What happens to the intensity 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 f-:ws,d5 -f j6uoi bzvhrom a sound source that is radiating equally in all directions. What happens to the intensity level of the sound:d- 6b,jzhowi sv-u5f? 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 a soun(c e 9owfsks154 x.anrd 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 ch8t vvd8zg)z; y(-y-jaxt6h wi aracteristic of the soy6ig t8hdzvw ;tj8-(-xa )yv zund 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 a 3.b ld7ju4hn tmusical 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 o0e* .ugad/qal 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 waterr*i n ti5 6j2rg,v1tzt

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 displac:jm c94e q(qlt zv9yl5vvq(t :, y.rrxement waves 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 string and the sound wave generated4bk)9 la- of hzukb6t- kj,z.d by the guitar as a result of this vibration. What do these two wavekbau.-oj -hklbt dk69fz)4z, s 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 which is open at both ends, thepv- d 4nsxvsi 5qw;d-xz6v0t; :xp0 cxre

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 v-0u)s 7 ;m 1 rcn*uog)s/jd;befp yy)5hszxtlength L. What are the wavelengths of the three lowest tones produced)o;-7mv /c;usu)sezp1)jryb nx s5d tg*yf0 h 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 re2l9vagwk6r )moscb/ ve+ jib:y ++*v rsonate in an open pipe of length L is 200 Hz. Which one of the foley+il9r kwr:j )2+/ svg+*b6vbvcaomlowing frequencies 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 resonatingmm *xl ysq19+q pdm7m9 at its fundamental frequency. Which statement is cormp1d97mqs ml9 xmq* y+rect?

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 is openk+5h wg,g q5kn 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:a ) 8iyoqyg)trbat6 k /fhuqv;5o4g4 wavelengths of the three lowest tones produced by 6:4boo;f tvqggauti ah5rq8)4y/k ) ythis 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 cj h/zm q* 6u 37yaloywqmc+0j2losed pipe of length L is 200 Hz. Which of the following frequencies will not resonate in that piph+mjom * lq2w azyjy76/cu0q3e?

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 closed at one end is resonating at its fundamental freyp; o z 3m3wx7a*nnrm/quency. Which statement i/ya o3n*3mwznp7x mr;s 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 dr.faxi ng (e+;. cuzt6-ft;pvriven by the same source. Each speaker produces a tone with a frequency of 200 Hz on a day when the speed of s;gpifet. 6;+ tu v(-fanz.crxound 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, the two soun0sjv* ks ujv8e p42e6fd 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 a0horc mc+ 0o ixq-kq+m m9-oq)nd a particular beat frequency is heard. What happens to the beat frequency if the frequency of one ofr)0q m xk+ohqoo i+--c 9mcqm0 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 explaiuzgu6 ,tp9w52v7yxtdns

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 stati:)7+iszk w :m3zo wilfonary observer. The frequency heard by the observer z:l+z k )imos7 wfw:i3is

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.te rzzz,q*:u the observe qztz e:,zur.*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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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 +z fabw9j-2, v h+73na u9xrzgo/imko half-angle will decrease by a facz f w9jxbm g,rz+7nou/ha-+va 29i3oktor 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. Whadnj6-/l hqs/at is the air temperah s /-dnj6a/lqture?

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 speed of sound in airwu+uvu)y 1fm jr4nbbon.c 0/0 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 speeddwx63se18w.w m 0czje of sound in air is 340 m/s, a bat emits a shriek whose echo reaches it 0.0250 s s .0 ce1jmw8e3wzw6 xdlater. How far away was the object that reflected back 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 temperatu0myqeo-31;;em+ju v -wmo 2j wjp -hture 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 after seeuu+qbiw/s z,6u fd12hfj( t2v ing a flash of lightning, the distance to the lightning striket1s,j/idhw fz6 + vuq2f(bu2u 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 a cliff on a day the cf ) j2: ftc,w1uzcz+utemperature 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 the splash 2.5 s xj;iaj9boj 9 2e351ye q9oh; 4zorhzvlater. How deep is the well? (Ignore air resistance, and ass ;rv9ebha5421yhojx9 qz zjeoji3o;9ume 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 fre+,dp+4c u hngvquency 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 air atwd2all/ 8lr5k $23 \; ^{\circ}C$ 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 intensi+(wiytoa;w ( w2ger:rty $10^{-3} \; W/m^{2}$?

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 70-dB b02p1weqn h79ek p5tzsound?

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 twoekh q xoz.504o sounds with intensity levels of 70 dB and 40 d oqo0h.5xz ek4B?

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. Wh1a t amc1uw bmj7t+q/7hx9jd5at is the intensity level generated 5 1umtjbha7wq xj9t7 /am 1+dcby one engine?

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 source that in5zym )*dugcg9yq v*+s radiating equally in all directg*gmzd) * q5y9 cyun+vions 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 fromtem4,ru of ub)89cmik-:a p3n a source that is radiating equally in all directi3p 9m:ct)uf,naome-ukri b 4 8ons 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, which is assumed to be unifoxv b ;((5dzvzkrmly distributed in all direbk(xzv5zv;( dctions. 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 distpo e60tr u3++gqft ,8ce tq5svance 5.00 m from a barking dog. What would be the intensity level if two identical dov8 te6 qt0t rq+5f+3ugocsep,gs 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 the igyr jj0mt; :j+ntensity level is 60 dB. What is the intensity level (in dB) at a point 2jg0 tj jry;+:m.0 m from the source? Assume that the 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 / g .iyf7ym5m lmbui60dB. At what distance will it be 7u fyyb0756il.immg /m5 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 tones8:eao;p1s slay8eq lpvfmo ju/48)9 has a frequency of 1200 Hz. What is the frequency of e s)ylvjpamlu9/4po18;as 8so8f: eq 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 b.:o jiv- r;(s2z0m)evs hzw mopen pipe is 900 Hz. What is the length of the pipes0jb zze;-h2 wosmvvm :i)r.(?

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 res1 iyg, pga9f-yonate in an open pipe of length L is 400 Hz. What is the fp 91i,fga -yygrequency 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 length of 0.80 m. If the veloci nvo g-1d3zt6g3 yka8nty of sound in air is 340 vang83 zky-o1gtd6 n3 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 h)8/w8:lticb rt yg(u the 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 pipe closed at one end is 330 Hz. What is the fr/pk oir/cnyoi0r (47d ;ee6u pequency of theocyid6;ier(7e0p /k/onru p4 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 pi78 *qyne6l vlsv14i jgpe closed on one end that will have a fundamental frequenlj 7i n6vs14q8v*lge ycy of 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 room where the temperature m c ,d0im*y,cie,zv( f2ykbkcwox 5/1 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*yt-o7 sq0idf5;bst m(mm6 ktere 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 c) y6mi-i: ae3bjco+yof length 0.75 m is played when the speed of sound in air is 340 m/s. What is the fundamenymc)3c:ji 6yibae o-+tal 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: one is open and the other is closed on ot *g2t1b pe*trvvpd,0 ne end. If the fundamental frequency of thete*gv, t* vdp2bt0pr1 open 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)+8zholisw xr x;r)i 5/ify )u each emit a frequency of 800 Hz in air where the velocity of sound is 340 m/s. How much farther back would source 1 have toirz)o5) i)xsxrify ; /+lwuh 8 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 driven by the same frequencypg5:tbw el y05 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 the following is a possible the distance from the person to the otheb: wtp05y5elgr 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 and 444 Hz. Whatmhat9qp8di dj3 )aq0/ 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 cdwhb7 d/z0 y-of a musical instrument. If the tuner hears a beat frequency of 2 Hz, zcyhdw7b-/0d 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 tod--lmrvi l9+yv2 p.sounds produced by two horns are 6 m and 7 m respectively. What beat frequency is het2yrl i+md--. lpvov9 ard when the horns are 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 on two vizow zf2gwb-.r*u2 g)oolins in an orchestra are found to produce a beat frequency of 2 Hz when a frequency of 660 Hz is played. What percentage change in 2ofzog) brw z-gwu. 2*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-Hn;v + kfb b2joseg;w5+z sound source at twice the speed of sound. The observer hears a frequs+webf b kn+;5 ovg;j2ency 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 (norm8m ewf,bu rj+2al frequency of 1000 Hz) approaches a stationary observer at one-half the speed of sound. The observer hea r2bf8+,wmj uers 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 listener moves9j; jkww71fev q ;5rd yckgw51 with a speed of 30 m/s away from the source, what is the frequency heard by the observer? (The sound speed is 340 mwywdg5e7k51 r cvjk9q ; ;jw1f/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 travens s:(u (8yzltmm-:er ov6*qpling at 35 m/s on a day when the speed of sound through air is 340 m/y*( 6tqr-spv(unm e:so :m lz8s. 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 o2//m5uhah mue bserver when a train approaches with a speed of 30 m/s. The frequency of the train horn is 600 Hz and the speed of sound is 340 m/s. u2ehm mah/5u/

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 f8d(-:w7qiem);gg ):eo amh p+ z qejwwhistle. Take the speed of sound to be 340 :gjfeiwe (gqw;z)qd -p mo +7:)me8ahm/s. What 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 toward a statir6vpu0 2 zww+sonary train. The train blows its 400-Hz whistle. Takez 0+rpu6w 2swv the speed 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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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..yn :yjpto hw8acz10e;tj u- 1 The train blows its 400-Hz whistle. Take the speed of sound to be 340 m/s. What frequency do you hear?uwop tjy-jeat0 .z 18hcy:;n1

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 frvj8uf8fj0ne1po ( 1 zvom you at 120 km/h. It blows its whistle, and you hear n0 8u1pvf(18zje vj ofa tone of 400 Hz. Take the speed of sound to be 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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教师可以抽题组卷或一键复制本试卷，布置为在线考试或在线作业，全自动判分成绩一键排序导出，省时省力

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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 soutmt+ hnc( o:.zigjv,(nd in air is 340 m/s. What is the frequency heard by an observer if the observer is v.it jg,no:c(t +zh m(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 soun6d - shiyncj.1 t vicbzm87:x)d in air is 340 m/s. What is the frequency heard by an observeinc7s: dtiv 1 b8xj.6hmy) zc-r 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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教师可以抽题组卷或一键复制本试卷，布置为在线考试或在线作业，全自动判分成绩一键排序导出，省时省力

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84#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Sonar is used to determine the speed of an object. A 40-kHz signal is sent ou5 mz 5bx)ktq3dtga7)si b (iz:3wk*wht, and a 42-kHz signal is returned. Assum:ba7z 5i)d m tgk5 w)zk3whqs(t xb3i*e 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 conical shock wave pti-9d6x5 hv /jng:oqproduced 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-angle4(ribg*7i4bdetqmoy ;s. /fk8 o scr 1 of the conical shock 7(fty*rg 8cmb/;4kq o14.bersdosiiwave 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 States to Europe with a Mach numbeilu6,lhxl6h1nq 4w n6r of 1.05 where the air temperatu4u6q n6ilw h lln,x1h6re 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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