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General Physics 1
Quarter 2 - Module 4:
Mechanical Waves and Sound
Name of Learner: ___________________________
Grade & Section: ___________________________
Name of School: ___________________________
What I Need to Know
What is your favorite musical instrument? Whether it’s a guitar, a violin, a piano,
or a flute, the same concepts in waves and in acoustics can explain how they work. In
this module, you will see that the sound produced by musical instruments can be
described using wave mechanics.
The module covers:
- Lesson 4 – Mechanical Waves and Sound
After going through this module, you are expected to:
1. Differentiate underdamped, overdamped, and critically damped motion
(STEM_GP12PMIId-28)
2. Define mechanical wave, longitudinal wave, transverse wave, periodic wave,
and sinusoidal wave; ( STEM_GP12PMIId- 31 )
3. From a given sinusoidal wave function infer the speed, wavelength, frequency,
period, direction, and wave number ( STEM_GP12PMIId- 32 )
4. Apply the inverse-square relation between the intensity of waves and the
distance from the source ( STEM_GP12MWSIIe- 34 )
Module 4 Mechanical Waves and Sounds Source:https://www.vectorstock.com/royalty-free-vector/cartoon-musical-instruments-vector- 22524630
What’s New
Activity 2. Let’s Make Some Wave
Directions:
1. Get a piece of rope about 2 m long. Fix one end of a rope by tying it around a post
or a rod.
2. Have a single disturbance in one end of the rope. What is formed? This time move
that same end with a series of disturbances. What did you observe? The single
disturbance made in a rope is called wave pulse while a series of disturbances are
called wave trains.
Guide Questions: (3pts each)
1. How did you generate waves in a rope?
________________________________________________________________
2. What is transferred by waves from one place to another?
________________________________________________________________
3. What is necessary so that energy could be transferred by the waves produced by
a rope?
________________________________________________________________
What is it
Types of Waves
There are two types of waves: the transverse waves and the longitudinal waves.
These are mechanical waves that require a medium for propagation. Water waves and
rope waves are examples of transverse waves. On the other hand, light wave is an
example of electromagnetic wave, which does not require any medium for
propagation. Rope waves travel in a direction perpendicular to the direction of wave
motion. This kind of wave is what we call transverse wave as seen in Figure 1 below.
Source:https://www.google.com/search?q=rope%20wave&tbm=isch&hl=en&hl=en&tbs=rimg%3ACYMhx4MIWADNYRrOJF _15OLjZ&sa=X&ved=0CCUQuIIBahcKEwjo7_Wyvd7rAhUAAAAAHQAAAAAQGQ&biw=1519&bih=754#imgrc=82e8tq7ilS11HM
Figure 1. Transverse Wave
SCORE: ____/
On the other hand, longitudinal waves are waves which travel in a direction
parallel to the direction of wave motion or parallel to the direction of vibration (see
Figure 2).
Source:https://cnx.org/contents/FFC6Ygl0@3.2:yzEWB8wD/Longitudinal-Waves
Figure 2. Longitudinal Wave
Characteristics of Waves
Water waves are easily produced and observed. By touching one point on the
surface you can see the peaks of the waves form circles and move outwards from the
source of the disturbance.
Some of the characteristics used to describe transverse wave motion are
enumerated below (see also Figure 3 on the next page):
§ The high points are called crests or peaks while the low points are called
troughs.
§ The amplitude is the maximum displacement from the rest position. It is the
height of the crest or depth of a trough measured from the normal undisturbed
position.
§ The wavelength, λ, is the distance between two successive crests or two
successive troughs. It is also equal to the distance between any two identical
points on successive waves, for example points A and B, and points C and D.
§ The frequency, f, is the number of crests or troughs that pass a point per
second. This is equivalent to the number of complete waves generated per
second. Frequency is measured in terms of hertz (Hz).
§ In a periodic wave , the motion of each point of the medium is periodic with
frequency f and period T.
§ The period, T, is the time taken to generate one complete wave. It is also the
time taken for the crests, or any given point on the wave, to move a distance of
one wavelength.
T = 1/f
over damping: the condition in which damping of an oscillator causes it to return to
equilibrium without oscillating; oscillator moves more slowly toward equilibrium than in
the critically damped system (see Figure 4 in pink color)
under damping: the condition in which damping of an oscillator causes it to return to
equilibrium with the amplitude gradually decreasing to zero; system returns to
equilibrium faster but overshoots and crosses the equilibrium position one or more
times (see Figure 4 in red color)
Source:https://www.google.com/search?q=critical+damping&tbm=isch&ved=2ahUKEwj_ifD16N_rAhWiI6YKHYVYDRAQ2- cCegQIABAA&oq=critical+damping&gs_lcp=CgNpbWcQAzICCAAyAggAMgIIADICCAAyAggAMgIIADICCAAyAggAMgIIADICCAA6BAgAEEM6BwgAELEDEEM6BQgAELEDOggIABCxAxCDAVCeqi hYic4oYIfQKGgAcAB4AIABcYgB5gySAQM3LjmYAQCgAQGqAQtnd3Mtd2l6LWltZ8ABAQ&sclient=img&ei=N8FaX7-SCqLHmAWFsbWAAQ&bih=706&biw=1536#imgrc=Tbz39EQjfFODOM
Figure 4. Damp Harmonic Motion
Sound
- Intensity is the same for a sound wave as was defined for all waves; it is
I=P/A
where P is the power crossing area A. The SI unit for I is watts per meter
squared. The intensity of a sound wave is also related to the pressure amplitude
Δ p ,
I=(Δp)^2 /2pvw
where ρ is the density of the medium in which the sound wave travels and v w is
the speed of sound in the medium.
- Sound intensity level in units of decibels (dB) is
β(dB)=10log 10 (I/I 0 )
where I 0 = 10–^12 W/m^2 is the threshold intensity of hearing.
What’s More
Activity 3. Guess What?
A. Below is an illustration of a transverse wave. Identify the characteristic of the
wave that is called for in the given item. Write your answer on the space
provided below the figure. Refer to the description of each characteristic as
mentioned in the early part of Lesson. (1 point each)
Source:https://home.apu.edu/~disaak/gp2/resources/16sampleHWproblem.pdf
1. __________________ 3. __________________
2. __________________ 4. __________________
B. How are the frequency, period and speed of a transverse wave related? (3pts)
___________________________________________________________________________
___________________________________________________________________________
Activity 4. Problem Solving
Sample Problem:
The frequency of some approaching ocean waves is 2 Hz and the length between two
wave crests is 3 m. What is the speed of the ocean waves moving towards the shore?
Given: Formula:
f = 2 Hz v = f λ
λ = 3 m = 2 Hz x 3 m
= 6 m/s
Solve the following exercises. Show all necessary solution inside the box: (5 pts
each problem)
1. A vibration of frequency 5 Hz sends a wave of wavelength 0.8 m down a rope.
What is the speed of the wave?
SCORE: ____/
SCORE: ____/
B. Match the word in column A to the sentences in column B that best
describes the word/s. Write the letter of your answer on the space
provided before each number. (1pt each)
___1. Mechanical Waves
___2. Longitudinal Waves
___3. Periodic Waves
___4. Sinusoidal Waves
___5. Transverse Waves
C. Solve the following problems below showing all necessary solutions in
the space provided below each question. (5pts each)
1. A wave is modeled by the wave function
y(x,t)=(0.30m)sin[2π/4.50m(x−18.00m/st)].
What are the amplitude, wavelength, wave speed, period, and frequency of
the wave?
A. waves that require a medium for
propagation
B. the motion of each point of the medium
is periodic with frequency f and period T
C. waves travel in a direction perpendicular
to the direction of wave motion
D. waves which travel in a direction parallel
to the direction of vibration
E. vibration that propagates as an acoustic
wave, through a transmission medium
such as a gas, liquid or solid
F. special periodic wave in which each
point moves in simple harmonic motion
COLUMN A COLUMN B
2. What is the intensity in watts per meter squared of 85.0-dB sound?
What I Can Do
Activity 6. Feeling Sound
Directions:
1. Search for a rock music on your android phone and connect it to a speaker.
2. Place the speaker on a light table and start playing the rock music.
3. Place your hand gently on the table next to the speaker.
4. Increase the volume and note the level when the table begins to vibrate as the
rock music plays.
5. Increase the reading on the volume control until it doubles.
6. Observe what happened to the vibrations.
7. Record your observation on the table below
Data Observed:
Volume Vibration (weak-strong)
(2pts each)
Observation (shaking of the table)
(3pts each)
Soft
Medium
Loud
Very loud
SCORE: ____/
9. Which of the following is an example of longitudinal wave?
a. blue light
b. radio waves
c. water ripples
d. sound waves
10. A source of frequency 500 Hz emits waves of wavelength 0.2 m. How long does it take
the waves to travel 600 m?
a. 3 s
b. 6 s
c. 12 s
d. 60 s
11. A large ripple tank with a vibrator working at a frequency of 30 Hz produces 25
complete waves in a distance of 50 cm. The velocity of the wave is ___________.
a. 60 cm/s. c. 750 cm/s.
b. 5/3 cm/s. d. 1500 cm/s.
The figure below represents a sea-wave that causes a small cork (Z) to rise up and down
through one complete oscillation every 4 seconds.
Refer to this figure for questions 12-15.
Source:https://home.apu.edu/~disaak/gp2/resources/16sampleHWproblem.pdf
12. The amplitude of the wave is __________.
a. 0.5 m c. 1.5 m
b. 1.0 m d. 3.0 m
13. The wavelength of the wave is __________.
a. 0.5 m c. 1.5 m
b. 1.0 m d. 3.0 m
14. The horizontal speed of the wave is __________.
a. 4 m/s
b. 12 m/s
c. 0.25 m/s
d. 0.75 m/s
15. If the wave is moving to the right, after 4 seconds the cork (Z) will be at position
________.
a. P c. R
b. Q d. S
Additional Activity
Activity 7. Let’s Have Some Vlog
Directions:
1. Look for at least two stringed and percussion instruments like in the figure below.
2. Record yourself through a video while making sounds from the different instruments.
3. Describe how tones and vibrations are produced by each instrument by stating it on
your video presentation.
4. Refer the rubric in Table 1 for your guide.
5. Submit your output to your science teacher through his/her email.
Figure 5. Stringed and Percussion Instruments
Category Excellent ( 10 pts) Very Satisfactory ( 8 pts) Satisfactory ( 6 pts) Needs Improvement ( 4 pts) Concept The video clearly demonstrates a key concept. The video demonstrates key concepts. The video demonstrates a previous concept. The video does not demonstrate a clear concept. Design The quality and materials in the video are very well organized and understandable. The quality and materials in the video adequately organized and somewhat clear. The quality and materials in the video lacked some organization and 50% clear. The quality and materials in the video are not organized and lack clarity Final Product Final product looks professional and the concepts were visibly demonstrated. Final product looks decent and the concepts were somewhat demonstrated. Final product l required more revisions and the concepts were not clearly demonstrated. Final product looks unrefined and the concepts were not demonstrated.
Table 1. Rubric for Video Presentation
SCORE: ____/
Source:https://www.vectorstock.com/royalty-free-vector/cartoon-musical-instruments-vector- 22524630
Reference
Mechanical Wave: (2020, September 8). Retrieved from google.com: https://www.google.com/search?q=rope%20wave&tbm=isch&hl=en&hl=en&tbs=rimg%3ACYMhx4MIWADNYRrOJ F_15OLjZ&sa=X&ved=0CCUQuIIBahcKEwjo7_Wyvd7rAhUAAAAAHQAAAAAQGQ&biw=1519&bih=754#imgrc=82e8t q7ilS11HM Musical Instruments: (2020, September 8). Retrieved from google.com: https://www.vectorstock.com/royalty-free-vector/cartoon-musical-instruments-vector- 22524630 Transvers Wave: (2020, September 8). Retrieved from google.com: https://www.google.com/search?q=rope%20wave&tbm=isch&hl=en&hl=en&tbs=rimg%3ACYMhx4MIWADNYRrOJ F_15OLjZ&sa=X&ved=0CCUQuIIBahcKEwjo7_Wyvd7rAhUAAAAAHQAAAAAQGQ&biw=1519&bih=754#imgrc=82e8t q7ilS11HM Longitudinal Wave: (2020, September 8). Retrieved from google.com: https://cnx.org/contents/FFC6Ygl0@3.2:yzEWB8wD/Longitudinal-Waves Mechanical Wave: (2020, September 10). Retrieve from google.com: https://home.apu.edu/~disaak/gp2/resources/16sampleHWproblem.pdf Characteristics of Waves: (2020, September 10). Retrieve from google.com: https://courses.lumenlearning.com/suny-osuniversityphysics/chapter/16- 2 - mathematics-of-waves/ Harmonic Motion: (2020, September 10). Retrieve from google.com: https://www.google.com/search?q=critical+damping&tbm=isch&ved=2ahUKEwj_ifD16N_rAhWiI6YKHYVYDRAQ2- cCegQIABAA&oq=critical+damping&gs_lcp=CgNpbWcQAzICCAAyAggAMgIIADICCAAyAggAMgIIADICCAAyAggAMgII ADICCAA6BAgAEEM6BwgAELEDEEM6BQgAELEDOggIABCxAxCDAVCeqihYic4oYIfQKGgAcAB4AIABcYgB5gySAQM3Lj mYAQCgAQGqAQtnd3Mtd2l6LWltZ8ABAQ&sclient=img&ei=N8FaX7- SCqLHmAWFsbWAAQ&bih=706&biw=1536#imgrc=Tbz39EQjfFODOM Websites Sound: (2020, September 10). Retrieve from google.com: https://courses.lumenlearning.com/physics/chapter/17- 3 - sound-intensity-and-sound-level/ Mechanical Wave: (2020, September 14). Retrieve from google.com https://courses.lumenlearning.com/suny-osuniversityphysics/chapter/16- 2 - mathematics-of-waves/ Rubric: (2020, September 14). Retrieve from google.com http://veralisteportfolio.weebly.com/uploads/5/5/2/8/55283737/video_integraton_project.pdf Books Arevalo, R.L. DIWA. (2017). General Physics 1. DIWA Learning System Inc. Padua, A.L., et.al. Vibal. (2003). Practical and Explorational Physics. Vibal Publishing House, Inc. Writer: Andrhea Mae B. Sumamban Editors: Margie Lou C. Jacob Laarni A. Adonis Kathleen Joy B. Padilla Joly C. Baradero Reviewer: Sandy R. Albarico Illustrator: Layout Artist: Management Team: Majarani M. Jacinto, CESO VI SDS-ZDS Visminda Q. Valde, Ed.D ASDS Raymond M. Salvador, Ed.D ASDS Juliet M. Magallanes, Ed.D CID Chief Florencio R. Caballero, DTE EPS-LRMDS Sandy R. Albarico EPS-Science Adiós, Patria adorada, región del sol querida, Perla del mar de oriente, nuestro perdido Edén! A darte voy alegre la triste mustia vida, Y fuera más brillante, más fresca, más florida, También por ti la diera, la diera por tu bien. En campos de batalla, luchando con delirio, Otros te dan sus vidas sin dudas, sin pesar; El sitio nada importa, ciprés, laurel o lirio, Cadalso o campo abierto, combate o cruel martirio, Lo mismo es si lo piden la patria y el hogar. Yo muero cuando veo que el cielo se colora Y al fin anuncia el día tras lóbrego capuz; si grana necesitas para teñir tu aurora, Vierte la sangre mía, derrámala en buen hora Y dórela un reflejo de su naciente luz. Mis sueños cuando apenas muchacho adolescente, Mis sueños cuando joven ya lleno de vigor, Fueron el verte un día, joya del mar de oriente, Secos los negros ojos, alta la tersa frente, Sin ceño, sin arrugas, sin manchas de rubor Ensueño de mi vida, mi ardiente vivo anhelo, ¡Salud te grita el alma que pronto va a partir! ¡Salud! Ah, que es hermoso caer por darte vuelo, Morir por darte vida, morir bajo tu cielo, Y en tu encantada tierra la eternidad dormir. 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