physics course exercisesIstituo Superiore Enrico Fermi - Mantova

the physics of sound

in accordo con il

Ministero dell’Istruzione, Università, Ricercae sulla base delle

Politiche Linguistiche della Commissione Europea

percorso formativo a carattere tematico-linguistico-didattico-metodologico

scuola secondaria di secondo grado

teacherFederica Motta

the physics of sound

Indice Modulo

Strategies – Before Prerequisites Linking to Previous Knowledge and Predicting con questionari basati su stimoli

relativi alle conoscenze pregresse e alle ipotesi riguardanti i contenuti da affrontare

Italian/English Glossary

Strategies – During

Video con scheda grafica Keywords riferite al video attraverso esercitazioni mirate Conceptual Map

Strategies - After

Esercizi: Multiple Choice Matching True or False Cloze Flow Chart Think and Discuss

Summary per abstract e/o esercizi orali o scritti basati su un questionario e per esercizi quali traduzione e/o dettato

Web References di approfondimento come input interattivi per test orali e scritti e per esercitazioni basate sul Problem Solving

Answer Sheets

1

Strategies BeforePrerequisites

2

the physics of sound

can be approached in

after teaching

after teaching

after teaching

2

Strategies BeforeLinking to Previous Knowledge and Predicting

sound

music physics

biology

Acoustic apparatus

anatomy and physiologyPlaying and singing

techniquePentagram reading

Goniometric functionsElastic forceHarmonic motionMechanical energy and power

3

the physics of sound

1. Are you able to define the sine of an angle?

2. Are you able to define the radiant as the angle international unit?

3. Are you able to draw the Cartesian graph of the sine function?

4. Are you able to define the elastic force?

5. Are you able to write the displacement, velocity and acceleration laws for a

harmonic motion?

6. Are you able to demonstrate that an elastic force causes a harmonic motion?

7. Are you able to write the kinetic energy and the elastic potential energy formulas?

8. Are you able to demonstrate that total energy in a harmonic motion is constant and

calculate its value?

4

the physics of sound

3Strategies Before

Italian / English Glossary

Ampiezza AmplitudeCinetica KineticDiapason Tuning forkElastica ElasticEnergia EnergyFase PhaseFunzione goniometrica Goniometric functionInfrasuono InfrasoundIntensità IntensityIntervallo (di valori) RangeLongitudinale LongitudinalLuce LightLunghezza d’onda WavelengthMeccanica MechanicalMezzo MediumMoto armonico Harmonic motionOnda WaveOscillazione OscillationPercepire To perceivePeriodo PeriodPerturbazione PerturbationPipistrello BatPressione PressureSeno SineSferica SphericalSuono SoundSuperficie SurfaceTemperatura TemperatureTerremoto EarthquakeTrasmissione tv TV broadcastingUltrasuono UltrasoundVelocità Speed

5

the physics of sound

4

Strategies During Keywords

1) Circle the odd one out: a wave can be

spherical – plane – longitudinal – transverse – chemical - harmonic – mechanical – elastic – periodic – seismic

2) Circle the odd one out: a wave has got a

frequency – wavelength – amplitude – phase – period – speed – direction of propagation – direction of oscillation – energy – tangent function graph - medium of propagation – source – intensity – sine function graph

3) Circle the odd one out: a sound has got a

frequency – wavelength – amplitude – phase – period – speed – direction of propagation – energy - propagation in steel – source – intensity – propagation in a vacuum

6

the physics of sound

5

Strategies During Conceptual Map

Complete the conceptual map using the following words:

frequency - gas - oscillating source - longitudinal

wave

medium

ear

From

through

to

liquid solid

sound

is a

spherical

parameterswith her

wavelengthamplitude

range

20 Hz 20 kHz

7

the physics of sound

6

Strategies After Multiple Choice

1) If two sound waves have the samea. frequency, they have the same wavelength toob. amplitude, they have the same period tooc. period, they have the same frequency tood. wavelength, they have the same speed too

2) The speed of propagation of a sound wavea. in a gas depends on the pressureb. depends on the nature of the source and not on the mediumc. is always independent from the temperatured. is a fundamental nature constant

3) A wave with a wavelength of 10 cm spreads out in the air. It is:a. an ultrasoundb. a soundc. an infrasoundd. a 34,3 Hz sound

4) A siren emits a 500 Hz sound. Its wavelength in air is: a. 0,688 mb. 1,46 mc. 0,688 cmd. 1,46 cm

5) A bat emits an ultrasound with λ = 6,8 mm that spreads out in the air with a speed of 343 m/s. Its frequency is:a. 5,0 103 Hzb. 5,0 104 Hzc. 5,0 105 Hzd. We don’t know the ultrasound physics laws

6) A music piece can be played at different volumes. That is, you can change its:a. period b. frequency c. wavelengthd. amplitude

7) The intensity of a sound is 10-6 W/m2 at 2 m from the source. At 10 m from the source it will be:a. 4 ∙10-7 W/m2

b. 4∙10-6 W/m2 c. 1 ∙10-6 W/m2

d. 4∙10-8 W /m2

8) A harmonic wave has a wavelength of 2 m and a frequency of 5 Hz. Its speed is:a. 0,1 m/s

8

the physics of sound

b. 0,4 m/sc. 10 m/sd. 2,5 m/s

9) You drop a stone in a well deep 9,50 m. After how much time will you hear the splash (v = 343 m/s)?a. 1,39 s b. 1,40 s c. 1,41 s d. 1,42 s

10) The equation of a wave is y = (6,0 mm) sin [ (3,25 m-1)x-(7,22 s-1)t].What is the speed value?a. 0,450 m/sb. 1,41 m/sc. 2,22 m/sd. 3,16 m/s

9

the physics of sound

7

Strategies After Matching

Match the results on the left with the correct data on the right:

1) v = 3,43∙102 m/s a) λ = 14,6 m = 4,40∙102 Hz

2) v = 5,01∙103 m/s b) λ = 14,6 m = 1,01∙102 Hz

3) v = 1,47∙103 m/s c) λ = 146 m T = 2,91∙10-2 s

4) v = 6,42∙103 m/s d) λ = 2,19 m T = 2,27∙10-3 s

5) v = 9,65∙102 m/s e) λ = 0,800 m = 4,40∙102 Hz

6) r1 = 1,00 m r2 = 1,95 m f) I1 = 2,80 ∙10-6 W/m2 I2 = 1,55 ∙10-7 W/m2

7) r1 = 1,00 m r2 = 4,25 m g) I1 = 2,80 ∙10-6 W/m2 r1 = 1,00 m

8) r1 = 140 m r2 = 8,63 ∙103 m h) I1 = 2,80 ∙10-6 W/m2 I2 = 7,40 ∙10-7 W/m2

9) P = 3,52∙10-5 W i) I1 = 9,9 ∙10-6 W/m2 I2 = 3,80 ∙10-7 W/m2

10) r1 = 27,4 m r2 = 140 m l) I1 = 3,80 ∙10-7 W/m2 I2 = 1,00 ∙10-10 W/m2

10

the physics of sound

8

Strategies After True or False

State if the following sentences are true (T) or false (F).

1) Changing the medium of propagation, the sound speed changes.2) Changing the medium of propagation, the sound frequency

changes.3) Changing the medium of propagation, the sound wavelength

changes.4) Changing the sound amplitude, the note you hear changes.5) Changing the sound frequency, the note you hear changes. 6) Increasing the sound amplitude, its intensity decreases.7) Doubling the sound amplitude, its intensity doubles.8) Doubling the sound amplitude, the energy it carries quadruplicates.9) You can hear on the Earth an explosion from the Sun.10) You can hear supersonic waves.

T F

T F

T F

T F

T F T F

T F T F T F

T F

11

the physics of sound

9

Strategies After Cloze

Complete the sentences with one word.

Oscillations often make waves which carry ......................... [1] away from the place where the wave started.The time it takes any of the oscillating parts of the wave to repeat its motion is called the .......................... [2]The energy contained in a wave is directly proportional to the square of the ............. [3], which is measured from the ............. [4] of oscillations at its highest value.Waves such as sound, where the oscillations are in the wave directions, are ............. [5]

12

the physics of sound

10

Strategies After Flow Chart

Complete the flow chart.You can use the terms listed below:

start

13

the physics of sound

11

Strategies After Think and Discuss

The following activity can be performed in a written (A) or oral (B) form. The teacher will choose which students are better in each ability.

The contexts in which the task will be presented to the students are:

A) the student is writing an article about physics of sound for a music magazineB) the student is preparing for a talk in an intermediate school to show younger pupils a sample of his high school activities.

In both cases the student should choose which contents are more suitable, outlining the main points of the argument, on the basis of what has been studied.

Either write the article, indicating the target of readers to whom is addressed.

Or simulate the talk to the whole class with a debate at the end.

end

Air molecule begin to oscillate.

I strike a bell.

Your ear receives the sound.

Energy spreads out as well.

Oscillation spreads out with a spherical symmetry.

14

the physics of sound

12

Strategies AfterSummary

A wave is a perturbation of the physical state at one place that propagates through space.Many phenomena are concerned with wave motion, among which sound.Sound needs an oscillating source and a medium to propagate.The physical property getting perturbed is the displacement of each medium particle relative to the equilibrium shape: sound is a mechanical, elastic wave.Sound is a longitudinal wave, as displacement is oriented along the direction of propagation and a spherical wave, as it is symmetrical in the three directions.Speed is typical of both the medium and the kind of wave. For example, in air its value is 343 m/s.Displacement (s) can be represented by the mathematical functionS = A sin (2 (x/λ – t/T))A is the amplitude, that is, the maximum displacement from the equilibrium shape.The sine function is known, as well as its angular periodicity 2.x/λ and t/T, being goniometric functions arguments, are pure numbers.X is the direction of propagationS, represented on the y axis, is actually along the X direction.If we fix a time instant, we project on the X axis the special shape of the wave.If we fix a space point, we project on the X axis the time evolution of the harmonic motion.The wavelength λ represents the space, the period T represents the time period of the curve.Instead of T, we usually indicate the frequency = 1/T as a wave parameter.As the wave covers a λ space in a T time, its speed is v = λ/T = λ . depends on the source, V on the medium, so if v changes, λ also changes.The wave identity is given by its frequency.We call sound the longitudinal, elastic wave perceived by human ear.Sound has a frequencies range from 20 Hz to 20 kHz, and a minimum amplitude of about 10-10 m.Ultrasounds have frequencies higher than sound.Infrasound have frequencies lower than sound.

15

the physics of sound

1) Answer the following questions. The questions can be answered in a written or oral form, depending on the teacher’s objectives.

a) What are the characteristics of any wave?b) What are the characteristics of a sound wave?c) How do you relate physics and musical parameters?d) What does the sound speed depend on?e) Which kinds of energy are involved in the sound propagation ?

2) Write a short abstract of the summary (max 150 words) highlighting the main points of the video.

16

the physics of sound

Web ReferencesYou can find a topic about sound in every website from a Physics University course. Here we give general references from which you can get formulas, test, simulation applets, animation, videos, data-bases.

By the Physics in Society team at the Institute of Physics. Its aim is to inspire people of all ages about physics. It is a guide and shows the best physics places on the webhttp://www.physics.org/aboutus.aspphysics.org

By Georgia State University, HyperPhysics is an exploration environment for concepts in physics which employs concept maps and other linking strategies to facilitate smooth navigation http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html

Short and rigorous stuffhttp://scienceworld.wolfram.com

Physics linked with all day lifehttp://physics.about.com

MIT, the best physics university in the worldhttp://scripts.mit.edu/~tsg/www/

Another US university website, with good appletshttp://www.colorado.edu/physics/2000/index.pl

17

the physics of sound

13

Activities Based on Problem SolvingSolve the following problems:

1)A dipper in a ripple tank makes 8 complete oscillations in a time of 2,0 s. When it is just about to make the 9th, the first has travelled 48 cm from the dipper.Calculate, explaining how, the frequency, the wavelength, the speed. Express the results in scientific notation, paying attention to the significant figures.

2) Primary earthquake waves travel at 7,5 km s-1, while secondary ones travel at 4,5 km s-1. What is the delay between the two types arriving at a seismographic research station 8,0 105 m from the centre of the earthquake?

3) A water wave has an amplitude of 50 cm. A wavefront of this wave carries 250 kJ of energy. What would be the energy carried by the same wavefront with the same wavelength but an amplitude of 150 cm? Does the answer change if the zero digits of the data aren’t significant figures?

4)A lamp gives off an intensity of 0,4 W m-2 on a newspaper 2 metres away.What is the output power of the lamp?What is the intensity 4 m away from the lamp?Justify the number of significant figures.

5)Draw a graph of the displacement of a particle in a longitudinal wave against distance from the source. The amplitude be 10 mm and the wavelength 2,0 m.Label the points A B C D E at a distance of 0,5 1,0 1,5 2,0 2,5 m from the point of origin.Write down the letters of:All the points at which the speed of the particle is a maximumAll the points at which the acceleration of the particle is a maximum Two points which are in phase.Two points which are 90° out of phase.

18

the physics of sound

Answer Sheets

Keywords:

1) chemical2) tangent function graph3) propagation in a vacuum

Conceptual Map:

wave

oscillating source

medium

ear

From

through

to

gas liquid solid

sound

is a

sphericallongitudinal parameters

with its

frequencywavelength

amplituderange

20 Hz 20 kHz

19

the physics of sound

Multiple Choice:

1 c, 2 a, 3 b, 4 a, 5 b, 6 d, 7 d, 8 c, 9 d, 10 c

Matching:

4a, 3b, 2c, 5d, 1e, 7f, 9g, 6h, 10i, 8l

True or False:

1 true, 2 false, 3 true, 4 false, 5 true, 6 false, 7 false, 8 true, 9 false, 10 true

Cloze:

1 Energy, 2 period, 3 amplitude, 4 centre, 5 longitudinal.

Activities Based on Problem Solving: 1) 4,0 Hz 6,0 10-2 m 2,4 10-1 m/s2) 71 s3) 2,25 MJ 2,3 MJ4) 20 W 0,1 Wm-2

5) B and D A, C and E A and E any adjacent pair

20

the physics of sound

Flow Chart:

Materiale sviluppato da eniscuola nell’ambito del protocollo d’intesa con il MIUR

start

I strike a bell.

Air molecules begin to oscillate.

Oscillation spreads out with a spherical symmetry.

Energy spreads out as well.

Your ear receives the sound.

end

21