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 d9y0/qqjvgf1 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 u9 xn0,mp9,xfuddklpspoifv1 8 i( +, c9 m-dgthrough

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 stee,f4nx w2wo,2ho- a4gzw9jauz l 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 happe4hasoci*(f q/a:p- e,), obaoh dxbl8ns to the velocity of sound? (Assume that all other factors remainep,:aoo q4ob-flia,)* a (8d bsx/hh c 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 200 Hz 2pzgjc:4s wuc .)wu 6rsound through2pzr.us)4 cgjw:u 6wc 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 wavelengx1 p-gzfnld+k 4yn a49th of a 200 Hz sound in air panzxn-9k41g 4ly fd+ 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 greatez7w8ou si+ .mor 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 -qb-t pk-fk- yless 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 is emitting waves uniformly ilp ;7 yozj72qcn all directions. If you move to a point twice as far away from the y; z7j qpol72csource, 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, ;v4p+ bqk/m-p3fue t bintensity 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 distg3v7 kt2firyxk t4k8pv pu668ance d from the source is I. What is the intensity at a distance 2d 466ktkirfkv 7g3yxppu 2 v88t 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 equally irf)2g5d2dgtg n all directions. What happens to the intensity of the sog)g d2 5tfdrg2und? 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 froms * ;u+6a i y332n4inzvkposwb/r9 uc8hysss. a sound source that is radiating equally in all directions. Wha ioun3 ny v.ras2wby36s9;z84+cskss /p*uh it happens 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 increass i: 9jc;.btqnes 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. n:ogg3 uajw.9 What characteristic of the sono au wj:9.g3gund 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 musical notogrb2on r/0v) e?

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?jdr l2y-zu1/pha y2z 9 o*jbh*

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 ab46elsq t6pp lgif5 1n-y48- szgw1* re*laoiir 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 displacs gb87be1m1gk ement 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 strinpva), udgch+ u11 if 9f)lj5qj0w9qfz g and the sound wave generated by the guitar as a result of thil5 i)uv)gd910fq, afjzhp 1f 9 ucj+qws 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 open at both ends, there1j3p mru .k8pp

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. What are the wavelengths of 1i9l xvyb.3wqe+ rzy1 the three loweste bwvyx1 l3r.19+yiqz tones 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 reson)g 9a,xc ervjv9m(i d.)gx/wuy s,/eqate in an open pipe of length L is 200 Hz. Which one of the f x,/a9gjugdwmir (q cev.ev x)) ,9y/sollowing 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* tonbzhk 3rc7+6x22f dkj10pqz+ye q is resonating at its fundamental frequency. Which statement is co+k7zf2n3ozpj *rkh6dbqqyxe2 t c1+0 rrect?

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 open at one end am zdx7q4:7,zj2lif/-tovm v bnd 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 wavelenw85z0met b-v p 7ha.u,ivawz .gths of the three lowest tones produced w0e. - zi.7 a8pzwv a5mu,hvbtby 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 Hz. Which of4h)(giy *+vc voyj/v*1wfllq e2ut dct+)m5r the following frequencies will not resonatcgil)qrdyye 2mlt 1v/54 ujvt*f) hwv++o *(ce in 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 closed at one end is resonating at its fundamena/ew)w a ; f(x)x d.1wjlavvr3tal frequency. Which statement is co) wv axawr3wa(xj/;fed 1)v.lrrect?

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. Each speak byen6xgbgk3xg x1. )c:*z6cw5vo rg,er produces a tone with a frequency of 200 Hz gr1* onw3)c6 65ecxvkby:xx, .g bgzgon 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, the two sound waves should hp/yghgcbmp:h 498w3yave

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 frequ;*fnmu:p (8e rimfxb 9ency is heard. What happens to the beat frequency if the frequency of one of the tones is increasenm8fbm9r*;fu(:ei px d?

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 explainv-, zsb+h(xlpue4/ y ns

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. uw c ro 9fgz4wa)dsv(s(g210eThe frequency heard by the obse21r (z edf sowsca)gwu v94(0grver 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 t l/y44tcw..ogh* bup 8,egy sfrom a stationary observer. The frequency heard by the observertbw,c.og 4t u 48*y les.g/phy 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, itrxt 33r* ntssdf)6,mns half-angle will decrease by a factomxtd 3fs*6,rrt)nsn3 r 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 i0yff /ar;9 f)is1 f qhzd0ik6 7l6asnns the aik;fas0s1 f hi6 n f7z9yirf0)nadq6l /r temperature?

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 of6cwe5a-2 :falo4lr mr the speed 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 bat emits a shriekhy;k4ofnir,of6: d *s whose echo reaches it s i ny,fdoo:*6kh; fr40.0250 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 4.00 s. The tempe;i5, 8otq-awz t sjkv:rature 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 ligfwca we40((gb xq+o 3uyxq7z7htning, the distance to the lig e wxbza7q40f3(c(g+u oy7 xwqhtning 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 clil+i :u8oj ei1;- fu io1rzd7owff 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 -y*snubv; n;0lbra 4h a deep well and hear the splash 2.5 s later. How deep is the well? (Ignore air resistance, and assume the velocity of sound is 340 mnlb; y4s*0hrvuna;b- /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 o ipp * vf,0ipi ubs*8kvbj.l1:f 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 ais9qntl tg . 4 ,nesyj/.135cgwbgnx3wr 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 m 6uifnig 1i) g/e pmko*40g.pwith 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 intensity of a 70-dB sou cs8dta4q-h4l .a :8z1 nlxixsnd?

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 int t pikdth5a* fy1;eb0vl71-rrensities of two sounds with intensity levels of 70 dB and 40t1ar veky1-bil0 p7rht* ;5f d 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 is5w fb eh:h9a8h the intensity level generated by of hw :9a5b8ehhne 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 is radiating eq) r-mk gslrb2)ually in all dire))r2- lrb smgkctions 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 that is t2 sahmq6g6u4 v, py9pradiating equally in al 6tp6 94s2pq,mvu ahygl directions 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*nr+k/32kt(dnb w zru about 1 mW of power, which is assumed to be uniformly distributed in all directions. What is the intensi3kwk b+ n/*nt(rd2urz ty 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 f)z vaas0, vp4n3zg a3srom a barking dog. What would be the intensity level if two identical dogs very close to each other area0szzn4) s pva3,a3gv 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 fr2 ng mj4q1p+q hn*;cy90x;ot5yroaz kom a sound source the intensity level is 60 dB. What is the intensity level (in dB) at a point 2.0 m from the sourp04 j5aq tc2q*z;;9o+x1kygnhm ry on ce? 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 leiv(s9co v4* cr+udv-xvel 5.0 m from a point source is 95 dB. At what distance will it be 75 dBd c+ouv *s-4xv irc9(v?

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 a5g icsr6w85ta d)7k+d q7d zje frequency of 1200 Hz. What is the frequ55ti)s 8+zderk adc6gj7 dw7q ency 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 ; 8iawf* 8+jyinx1nu xis 900 Hz. What is the leng*+ai w8xn fji y;8ux1nth of the 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. Wha3j/* 9uuf,ag pz ooudox49-gyudc 0 ,dt is the frequency of the lowest tone that will resonate in an open pipe o43 yg0cj/fp-,ddo9gu x u aduo*o z,u9f 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; r9nvy15sfi6e c8 nvy the velocity of sound in air is 340 m/s, what is the frequency of the sr69 n n1 f8ei5vvycy;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 w9z zo:(.+bk h.x* obuvx/ds ni* ttm.bhere 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 bzq 0mkx+4-yr qmz0k,one end is 330 Hz. What is the frequency of the third harm4zkk+qx q,ym-r0mb0 z onic?

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 r8gv jdrv9dn3;kjyn,m(;i 6n)m y+kx will have a fundamental frequency d+jnnxm 9;)vd6vk;yrrimg j(8,n y3kof 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 temperatur+thqz 21nueq3 e 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 where the tempera*t v73yoml; aypkx3: bture 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 gc 3yg*9sq w0a0.75 m is played when the speed of sound in air is 340 m/s. What is the fundamenta9sgwcy0 *3q gal 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,gc,o h*1+qpujw - h)2mruduy the other is closed on one end. If the fundamental frequency of the open dg+,,1o2u- ur wmh)j*cpuqy hpipe 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 velocs1 kt 9v.erxmm/8o pb6ity of sound is 340 m/s. How much farther back would source 1 have to be moved so an observervm/pe o tb6.kr9s1xm8 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+dj5 jqlhn/4ma63g gu1hae1w 6geoq 0 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 0h41/66amql dnqh e+u5 gowjg13jage 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 and 444 Hz. What is the beat frequency?0 :8esl2 stqun

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 inspvb ,3 b*4ic-qckw* hbtrument. If the tuner hears a beat frequency of 2 Hz, what is the frequency of the iwhq**- bcb v4pbkic ,3nstrument?

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);fp r eyxy;+hl3u 7.bs (zamc two horns are 6 m and 7 m respectively. What beat frequee uzs .yp rh)malxy 3+cf(b;;7ncy is heard 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 violins in an orchestra areb:rc p9rnj1 rgm7 rmo3,7dsk; found to produce a beadc:b7 rm71gkonr j3mr; r9,p st frequency of 2 Hz when a frequency 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 at twice the speeg vgow7)/ r,h q v0i9jh +ra9d8vgkf5kd of sound. The oj )gwvq, 0rh fkd5v9/kog8r+hagvi 7 9bserver 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) approaches a stationary observ0y+r3 s 0v7za878hmjf sjqwaker at one-half the speewqjsj 7s3v87 ryzm0a+8fa0 khd 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 Hz. If a listener moves w8( wafhr* gpzkg5y2v1 ith a speed of 30 m/s away from tvg ah(y 8* kg2fwzrp15he 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-Hz siren. It is traveling at 35 m/8+gox- l7sbbiq00u mcs on a day when the speed of sound through air is 340 m/s. The car approaches and passes an o+8 i sblubo7xmq0 c0g-bserver 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)(.0jvp:yskzxt fw f; heard by a stationary observer when a train approaches with a spe k ;xfjzv0w)( :ty.fpsed of 30 m/s. The frequency of the 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 you at 120 km/h. The train blows its 40s h/54l) 7pcc:isrsuv 0-Hz whistle. Take the speed of sound to be 340 m/s. What fr:pl4r 7/s)sic uhvs5cequency 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 stationary train. Thvf )trgke7b 79g2/z rre train blows its 400-Hz whistle)/erz2 79v rbfrkgt7 g. Take 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 kk1 g hb*n//c w.+huorhm/h. The train blows its 400-Hz whistle. Take the speg/w c+bnu/o .*h1 hhrked 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 zh f2zp h tjn71x6+po6120 km/h. It blows its whistle, and you hear a tone of 400 Hz. Take the speehzozp ft xn667 1j+2phd 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 soundnb51 vntn6jk - in air is 340 m/s. What is the freq -b5j6nkv1tn nuency heard by an observer 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 sound in e9 b8 mtl;cwbu63p;mkwc,j 3uair is 340 m/s. What is the frequency heard by an o,wblukt ;39j cm ew;pm6cu3 b8bserver 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 (exfz 67dtxog rd7u-,of an object. A 40-kHz signal is sent out, and a 42-kH o,76e-t7f rudz(xdgxz 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 conical shock wave produced by a supersonicxi j8lr, 8rohofmeui14 dud41h u cuq*8q)g* / 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-angszz1ed yf ,2d2le of the conical shock wave f1sd y e,2d2zzformed?

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 fromk-o 1l1iha: fe the United States to Europe with a Mach number of 1.05 where the air hl11:f- oiaketemperature 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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