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 aq (u .llg;uj /pe:ar-x 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 fastesyayutq ;z40 5 gge oo68rl0ef:t 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 sound in a steel .ki jzg - +6ide9f/hlorod?

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 happens to tqe /x+ uos5:gyz8g* clhe velocity of sound? (Ass gexg8*qcu:y5 szol/+ ume 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 velocitvr3jk8h v :cjgt:;w+ qy of a 400 Hz sound, the velocity of a 200 Hz sound through air icwg3: jk vvh8r;:q+tjs

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 wavelen/pzyhyi(-v3)ot jljz*:u ri2gth of a 200 Hz sound inypr*/zz)3i uv:hi(lojjt-2y air 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 20,000 Hz axp+9nai f m)u.16vsy vre 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 frequencyeh w6oq3gr01a;un e)x less than 20 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 ij(k+el hz- 6ey)q;blxy *gz)ps emitting waves uniformly in all directions. If you move to lpz* q6jg-yyxl)khe b)+e z;( a point twice as far away 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 waves, intensity is propey zqx:*si5x, ortional 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 distan1jqdu-pkzw3 fd / o9:xce d from the source is I. What is t-o1dudwzj q fpx:9/3khe intensity 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 ivp*78 efsi *iss radiating equally in all directions. What happens to the intensity of the sound? It reduces ip8*f si*se7vto

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 nwr rse1ii/b9 92awai1 m u58gsound source that is radiating equally in all directions. What h9 5rg/1eaaiwbi2iw us89n1r mappens to 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 increases as a sound beco )pe9l (w:bprymes 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 emitt7 ;jcmvzqx cj sy-k8. i)vau.*ing a pure tone. What characteristic of the sounci kv)acz mjj-;.xs 7*y8v.q ud 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 mu r4buj ga.zws+ +oq97qsical 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 musical note? smye:sv 40 8el/j e65o4tsdyc

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 a0yyiu sv d64t .n,ov7xly7x/3mk 6qdsir into 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 m *dd2t,xq)dgp9 q-xiwaves 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 gena6 7/mexby c-) he6j 5wyw.umnerated by the guita.u5wynwm7 x a6be hj6cy/)m-er as a result of this 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 which is opnfk(v 22cyj 9qen 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 lg c),g-w6v.h otj9p:5d bymdzength L. What are the wavelengths of the three lowest tones pro- z95bj)tdd .m hvg 6c,gwpoy:duced 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 of length L is 200bc0ub avm5;ej fo5glxzweqb.k ,ik 6,r ::o(4 Hz. Which one of the following frequenc0 ab;wc4k:6 5v .kbj, lioumor,g f(xez :5bqeies 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-(eq 5;fhwa sc at its fundamental frequency. Which statement isawe f;q5sh (c- 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 whic-oxx t/t ;(s+u8ccedih 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 L. What are the wavelengths of dh25u2cxq)nr y8wgr vz) wu8t5 7ic(n the three lowest tones prodvui )zh d2g58n5uy7 x(w2r)nctrq8 wc uced 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 closed pipe of length L is 200 Hbhrc2ph q69w2hd 1;ms zd(pi 0 )fep/ez. Which of the following frequencies will not resonate in thatph/p0q(s;e2ez mf6ci19dwrp2d h hb) 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 closed at one end is resonating at its fundas q 87lov9wj1q qsne6ng8s *i6mental frequency. Which statement is corsqe o 169* wqg sj87il86nnqvsrect?

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 y;h 6:xfwj ;9762 gxyhe;c1e e, nomfjm3tkky speakers driven by the same source. Each speaker produces a tone with a frequency of 200 Hz on a day when the speed of sound is 330 m/s. The nj w x 6oxm3e;f7eek,y;6j ty1k:; 9hm2gc yfhperson 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 sound waves sho+ 4*alpr4fad l8vpdnkm8 ;1 oauld 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. Wzgxf *q/l d+brww, c84hat happens to the beat frequ8+wg* ,czwrl fbd qx/4ency 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 explainh6 cu7jjs/ctzx *6kbmh.8v 8zs

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. w174bbj afd6 zj l1s;wjbf-p6 The frequency heard by the obsjf ;jf 6p-wb6s1alb 71dbzwj4erver 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 ,sxt8kq1 i 1oj1d pdd9from a stationary observer. The frequency heard by the observer is1tjk1 idpqs1dx o8d9,

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 wisytl2yy 7.r-vl j9tj 4ll decrease by a factor of 2s jvll-r.ty947 jtyy:

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.rk5vvn1hc qdg)efly548 6kz; What is the air tem kgq4vey8hrk1zn; d5vl6f) c5perature?

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 air atwl+hi/b,lx il6ex0q8waosr .f-y,h . $0 \; ^{\circ}C$ 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 bat em ko85.wg+ ln+xf,r thxits a shriek whose echo reache kf+ x+hx5.gol wt8nr,s it 0.0250 s later. 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 p 0 ,4ii,kz j/qvs/ykg4.00 s. The temperature 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 seeing a flash of lightn0f3,4bw ge(q) rf/ x9lis/-m rem cewring, the distance to thebm- ql eiwe/30 wrg)r4 ff,/mx s9r(ec lightning 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 a cqw7)qnw2 +u fi6s/wxqliff 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 hear the splash 2m2(ba:gl : 6-h bb-ircnn pwo9.5 s later. How deep is the well? (Ignore air resistance, and assume the velocity of sr2bh69b ac :g mb(-ionpwn:l- ound 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 s ,.3:1msw6uzdom ) ;bc immpfbound wave of frequency 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 ai dcwvyyo;,-m+m o,v+p bh lg6/r 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 intensity u65k+:zbk l i45u1qyzzjb(e ler 2mb:$10^{-3} \; W/m^{2}$?

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 intensityx*lzoj1 l+ 7zj 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 intensities of two sw(b cm;mp :p(p;)t rg( w3ghykounds with intensity levels of 70 dB ah3m((y:pg; ( mcrktbp)ww; pgnd 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 ita-;sex* wx9.am9uwq n oy 48ls the intensity level generated by one engine.a4wxn;oa8u*9e lm9y xqswt - ?

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 distan i9l46s. qolx1 m.wo4h 5qvpwxce of 6.0 m from a source that is radiating equally in all directwoi 49p.mo xw6llxqvs. h541 qions 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 k0xahgy)f o) h5q:m5cof 6.0 m from a source that is radiating equally in all directions5yoh ck )xm0:qhfa5)g 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 assumekk0kkl8 n9j:c,8mywd d to be uniformly distributed: m n9,lwd88jckk0kyk in 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 distan)hay)b2r/soz*e4 ykm* ll3k8it af u2ce 5.00 m from a barking dog. What would be the intensity level if two identical dogs very clo3 umalk r/t*f)y hes kb 2a24)8zy*olise 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 intensity level is 60 wnna 8z /44p:id ohd2zdB. What is the intensity level (ind2/:dz8n4z4 owian p h dB) at a point 2.0 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 4nbi+2mf0a 3ocqr u* flevel 5.0 m from a point source is 95 dB. At what distance will it be 75 dB+af 34nrm2qc b0o*f ui?

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 is tilt,wd vcf1 z 2 zb).c9z3420otftoanhe frequency of tlfbwz t)401o ai3c 92 dtz, fcozvtn.2he 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. What iajj8n5rd -b/h4rkx vfru+sxdwb5c) 4 *i pm**s the length of tx-)fh / 8+*urbicdxk4rand*4 w*vmj rsbj 5p5he 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 resomdsfsa5t d;, (1ehh(t3 joo0onate in an open pipe of length L is 400 Hz. What is the frequency of the lowest tone that will resonate in an open pipe of l ; 1do(,fh5dh0ts sa(j et3mooength 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 thyodkp e(4g0c:e velocity of sound in air is 340 m/s, what iscoey:p(k d4g0 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 temperature(o2xyua3j 9n p 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 ao(.r k glnu xvh* :iom+c7a,:in a pipe closed at one end is 330 Hz. What is the frequency of th*(+ko:, vuimang.7 rh clx:a oe 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 hxnzgtiziz14gf12bt 6q tdz7/x/ ah /: ave a fundamental frequency of 60 Hz on a day 2b1/ zn tdx/i4: /76ggf 1ttxihaqzzzwhen 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 a3f pak s;m3+eg9 hjvt/ 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 room ;ax.;8eer s:2pb4 3 cnugydzqwhere 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 mpihd3.oe y1l7*n+dewg y o n(cg.8 kk* is played when the speed of sound in air is 340 m/s.eon17dgho* w+ gyelk8dip.n*k(3 c y. 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: one is open and the other is c guj- /wix4x8mlosed on one end. If the fundamental frequency of the open pipe is 300 Hz, what is8 imw4/xjgxu- 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 emmkf mf,r;ds s* x6(el5it a frequency of 800 Hz in air where the velocity of sound is 340 m/s. Hs mfx (r5f,m ldsk;6e*ow much farther back 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 t9brd 2+72tddzls4rbx2r i )wside by side and driven by the same 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 the following is a possible the distance from the petr)dx2bwz4dbd r t lis7r922+rson 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 and 444 Hz. What is tln0e*+it r*tkhe 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 music (s9(sy9tek fdzy1uu8 al instrument. If the tuner hea99dts u fseyk(u1y8(zrs 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 e*g7numsig j4j60m:s f tpp0;n q(w r/6 m and 7 m respectively. What beat frequency is heard when f04 mjsp/u* j0pis mgn: (et6ng;rqw7the 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 violiy bql,x 4(,sv:wc1llxns in an orchestra are found to produce a beat frequency of 2 Hz when a frequency of 660 Hz is played. What percentage changv x,l l,s( 1b:q4xlwcye 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 soufp l aoec 9.xu20sxgb8n +oc0;e9 eh7 8prdjw7nd source at twice the speed of sound. The observer hears a frfg9c9+07ow2pn.hd8sar x7 je 8ob;ecxe u0plequency 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 H(6+ajf/qvqf oz) approaches a stationary observer at one-half the speed of sound. T qajvqf/(6 of+he 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 100k c7;o11c4 ttlvgr,q14 uet in0 Hz. If a listener moves with a speed of 30 m/s away from the source, what is the frequency heard by the observer? (The sound speed is 340 m/s.ltutir 4qkc,4ev11g71 on ct;)

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 tr h v3+4gj33glmwxh/xvy qh xe43 e+hq,aveling at 35 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 standing alvhy3jvq h4 ++ lq,3 mg3 gx3/we4xxhehong 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 70 x2cjru)jio-ft8wm d i2zf4a stationary observer when a train approaches with a speed of 30 m/s. The frequency of the t)2 ijdmf 78t2ic-zour4 0fwj xrain 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 you at 120 km/h. The train blows its 4007wmp-5fzv/ 2)vwpx gd -Hz whistle. Take the speed of sound to be 340 m/s. What frequency do you h/pvpwv )d m2 xfwzg7-5ear?

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 stations e awt: p.6-jwapg7c9ary train. The train blows its 400-Hz whistle. Take the speed of 7wc 6.a:p9-s wjteg apsound 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 vm+6djae+-6i-x qayes4 qo5v from you at 120 km/h. The train blows its 400-Hz whistle. Take the spev +qvyd6eiqo 5-mea sj4+ax-6 ed 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 away from you at 1+- 22 xy eqzoasn/zio-20 km/h. It blows its whistle, and you hear a tonoe n2/+- x-qo ysz2ziae 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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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 soun e1o 8ofuxt)(z-/ndlod in air is 340 m/s. What is the frequency heard by an observer if the observer is moving a lo/f-z n x1(toou)d8eway 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 H* tzsjyx(j +o2z. Assume the speed of sound in air is 340 m/s. What is the frequency heard by an observer if the observer isj*zy2jtx(+os 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 anlok d8: 1w7xnv object. A 40-kHz signal is sent out, and a 42-kHz signal is returned. Assume the speed of sound is 3458:v71dnwkl xo 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 produced by a supersonic aircra4 ;+f;dr/vloh8r. fnlazhr b1ft 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 1j.wlslz +5j,q4 i-owv.4. What is the half-angle of the conical shock wave formj -5o l+vzsq,j.il4ww ed?

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 numbey--kze6p z5pu r of 1.05 where the air temperaturyp-ze6k u- 5pze 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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