Test+FyBNVC09+Ch11 12+Waves Sound

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FyBNVC09 Ch11-12 Mechanical waves – Sound NV-College -INS

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Physics B

FyBNVCO09 Ch11, and 12 Mechanical Waves and Sound

Instructions:

Time: 140 minutes: 8:10-10:30

The Test At the end of each problem a maximum point which one may get for a correct solution

of the problem is given. (2/3/¤) means 2 G points, 3 VG points and an MVG ¤ quality.

Tools Approved formula sheets, ruler, and graphic calculator. You may use one page of a

personalized formula sheet which has your name on it. This should be submitted along

with the test.

Grade limits: There are 13 problem, 3 of which are ¤ MVG type. The test gives a maximum of 35

points of which 16 are VG points.

Lower limits for examination grade

Pass (G): 12 points

Pass with distinction (VG): 23 points of which at least 6 VG-points.

Pass with special distinction (MVG): 28 points of which at least 12 VG-pointsand most of MVG-qualities.

Problems number 10, 12, and 13 are heavily graded and are of greatest importance for

both VG and MVG. You may choose to solve these problems before solving the others.Waves Sting Pipe Pipe Bottle Standing W Earthquak Pitch Doppler Intensity Level

Problem 1 2 3 4 5 6 7 8 9

G 2 2 2 2 2 1 1 1 1

VG 1 1 1 1 1 2

G

VG

Waves Interference Doppler Organ Pipe Standing W Mechanical Waves

Problem 10 11 12 13 35 Total min G min VG min MVG

G 2 2 3 19 Total 12 23 28

VG 2 2 4 3 16 VG points 6 12

MVG¤ M235¤ M12345¤ M12345¤ M12¤¤¤3¤¤¤45¤¤¤ M12345¤¤G

VG

MVG¤





In the multi-choice problems below just circle the correct answer (s) in the test paper.

1. If a violin string vibrates at Hz588 as its second harmonic, what are the frequencies

of first three harmonics? [1/0]

a. Hz f 5881 , Hz f 17612 , Hz f 47013 ,

b. Hz f 2941 , Hz f 588

2 , Hz f 882

3 ,

c. Hz f 2941 , Hz f 882

3 , Hz f 4701

5 ,

d. Hz f 1471 , Hz f 294

2 , Hz f 5883 ,

e. None above, they are:

Why? Show a sample of your calculations. [1/0]

Answer:

Alternative ______

[1/0]

2. What is the length of an organ pipe whose

fundamental frequency is Hz440 at C 20 . How

long is the pipe, if it is open at both ends? At

C 20 , the speed of sound in air is sm / 343 .

a. cm5.19 ,

b. cm9.38 ,

c.

cm0.78 ,

d. None above, it is: _________________

Why? Show your calculations. [1/0]

Answer:

Alternative__________ [1/0]





3. If the air temperature in a room is increased, the fundamental frequency of the organ

pipes

a) will be increased.

b) will not be effected.

c) will be decreased.

d) will be equal to the frequency of the second harmonics.

Why? Explain and show a sample of your calculations. [1/0]

Answer:

Alternative_______ [1/0]





4. What resonant frequency would you expect from blowing an empty soda

bottle that is cm4.16 deep? What would the resonant frequency be if it

was %75 filled?

a. Hz262 , and Hz786 respectively.

b. Hz1046 , and Hz1834 respectively.

c. Hz523 , and Hz0902 respectively.

d. Hz953 , and Hz8582 respectively.

e. None above, they are:

Answer: Alternative ______ [1/0]

Why? Show your calculations in the space below. [1/1]

5. The velocity of waves on a string is sm / 0.94 . If the fundamental frequency of the

standing waves is Hz349 , how far apart are two adjacent nodes?

a. m08.1

b. cm9.53

c. cm9.26 ,

d. cm5.13

e. None above its ___________







6. In an earthquake, it is noted that a footbridge oscillates at fundamental frequency of

period s25.2 . What other possible resonant periods of motion are there for this

bridge?

a) ...,3,2,125.2 nsn

b) ..,3,2,14

9

ns

n

c) ...,3,2,19

4

ns

n

d) ...,3,2,125.2

2ns

n.

e) None above. It is …………………..

Answer:

Alternative ______ [1/0]






7. Of the following procedures, which one (s) will lower the pitch of a guitar string? i.e. it

will make its frequency smaller.

a) Decrease string tension.

b) Increase string tension.

c) Shorten the string.

d) Lengthen the string.

e) Use a heavier string.

f) Use a lighter string.


Why? Use words, formulas and logic in the space below to

show how you arrived in your conclusion. [0/1]





8. The siren of a police car at rest emits a sound wave at Hz6001 . What frequency will

you hear, if you are at rest and the police car is moving away from you at hkm / 108 .

a. I will hear the siren at Hz4711 .

b.

I will hear the siren at Hz7531 .c. I will hear the siren at Hz7401 .

d. I will hear the siren at Hz4601 .

e. I will hear the siren at Hz4602 .

f. I will hear the siren at Hz1851 .

g. None above. I will hear the siren at

…….


Why? Use words, formulas and logic in the

space below to show how you arrived in your

conclusion. [0/1]





9. The intensity level of the sound from a rock concert at a distance of m0.5 from the

main loudspeaker is dB130 which is the threshold of pain. How far away would the

intensity level be a somewhat reasonable dB100 ?

a. At m150 from the loudspeaker.

b. At m125 from the loudspeaker.

c. At m100 from the loudspeaker.

d. At m75 from the loudspeaker.

e. At m50 from the loudspeaker.

f. At m25 from the loudspeaker.

g. None above. At m from the

loudspeaker.

Answer:

Alternative ______ [1/0]

Why? Use words, formulas and logic in the space

below to show how you arrived in your conclusion.

[0/2]





10. Explain the phenomena of interference in words, formulas and necessary figures. What

are conditions for interference to take place? What are constructive interference versus

destructive interference? In the figure below identify points where constructive

interference, as well as points where destructive interference takes place. [2/2/M235¤]




© [email protected] Not for Sale. Free to use for educational purposes.☺10/11

11. An ambulance carrying a seriously injured patient moves down a highway at a constant

velocity of hkm / 126 . Its siren emits a sound at Hz.700 . Determine the frequency

heard by a car driver moving in the opposite direction at constant velocity of

hkm / 0.90 as the car approaches the ambulance. [0/2]




© [email protected] Not for Sale. Free to use for educational purposes.☺11/11

12. A particular organ pipe can resonate at Hz735 , Hz0291 , and Hz3231 , but not

any other frequencies between Hz735 and Hz3231 . [2/4/M1235¤]

a) Is this open or closed organ. Why? Show details of your calculation and explain

your reasoning.

b) What is the fundament frequency of this pipe?

13. The accompanying figure illustrates a

standing wave in a string at Hz735 .

It is produced by a frequency

generator. The string in the figure iscm0.51 . [3/3/M1235¤]

a) Calculate the wavelength of the

wave.

b) Calculate the velocity of the

wave in the string.

c) Explain in words in sufficient

details, formulas, and figures

what a standing wave is and

how it may be produced.

a) Which type of wave is the one in the picture? Longitudinal or transversal? What

are differences between longitudinal and transversal waves?

b) What will happen if the frequency of the generator is gradually changed? Will

any other standing wave occur if the frequency range of Hz200 to Hz5001 ?

If so, which ones and why? Explain in words in sufficient details, formulas, and

figures.

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