Speed of sound - WordPress.com · 2016-01-25 · Sound in different materials Which state of matter...

Speed of sound

How fast does sound travel?

© cgrahamphysics.com 2016

Starter - recap

Sound waves are

collected by the

pinna.

The waves

travel along

the ear

canal.

The waves

make the

ear drum

vibrate.

The small bones

[ossicles]

amplify the

vibrations.

The cochlea

turns the

vibrations into

electrical

signals.

The auditory

nerve takes

the signals to

the brain.

Put these Sentences in the right order:


Have you ever wondered…

Why is there a delay between a lightening strike and the thunder?

EXTREME Close Lightning in HD compilation! Loud thunder!.mp4





Objectives:

•Calculate the speed of sound

•Explain why sound travels at different speeds through different mediums

Speed of sound


Sound waves are vibrations and so need a substance to travel through.

With air inside, the sound can be heard.

With nothing inside [a vacuum], the sound can’t be heard.

What happens when the air is removed from the bell-jar?


Sound travels by particles vibrating. To understand this better you need to remember what the particles look like in a solid, liquid and a gas:

solid liquid gas

Which state does sound travel fastest through? Why?


Sound waves need particles in order to travel.

The substance that the sound travels through affects the speed of sound greatly.

330 350

1450

5000

6000

0

1000

2000

3000

4000

5000

6000

7000

Air at 0 C Air at 30 C Water Concrete Steel

Material


• Rabbits warn each other of danger by thumping the ground.

• Explain why this is more effective than ‘crying’ a warning.


Sound : How fast does it travel?

Most of us have seen thunder storms - which comes first, the thunder or lightning?

The lightning gets to our eyes before the thunder reaches our ears.

1) Thunder & lightning are made at the same time so we deduce that light travels much faster than sound.

2) In fact light travels so fast that:

the time between seeing the flash and hearing the bang = time taken for sound to travel.


Sound : How fast does it travel?

> 100m

00:0000

START

00:0034

STOP

1) When you see the cymbals crash, press START.

2) When you hear the cymbals crash, press STOP.


Experiment

Record the results of the sound experiment in a table like this:

Speed of sound – results

100 0.34 294 1

2

3

4

Distance (m) Time (s) Speed (m/s)

How are these values used to estimate the speed of sound?

=

100

0.34 294 m/s = speed =

distance

time © cgrahamphysics.com 2016

The first cymbal experiment gives an estimate for the speed of sound as 294 m/s.

Speed of sound – analysis

Use the average of your results to calculate another

estimate for the speed of sound.

1. How does this calculation for the

average speed of sound compare

with the real speed?

2. What errors could have affected the

results of the cymbals experiment?

3. Do you think the speed of sound in

water is the same as the speed of

sound in air? © cgrahamphysics.com 2016

Energy transfer

How many different energy transfers do you think take place

during this experiment?

When the sound waves reach the ear, there is a transfer of kinetic energy from the air particles to the eardrum.

kinetic energy of

cymbals

kinetic energy of air particles

kinetic energy in

eardrum

When the cymbals crash there is a transfer of kinetic energy from the cymbals to the air particles.


Sound needs a substance through which to travel because it

travels by making particles vibrate.

Sound in different materials

Which state of matter does sound travel fastest through?

The particles in a solid are closer together than in a gas,

and more tightly bound than in a liquid. This means

vibrations are more easily passed from particle to particle,

and so sound travels faster.

Sound waves travel fastest through solids.


Sound waves in different materials


Speed of sound in different materials


Which of these travel faster than the speed of sound in air?

Breaking the sound barrier

The jet fighter and the

meteorite travel faster than

the speed of sound in air.

This is called breaking the

sound barrier.

Movie Sound - Lesson 3 - Sound

barrier.flv

120 600 small aeroplane

jet fighter

cheetah

meteorite

Distance (m)

5

Time (s) Speed (m/s)

900

50

10,000

2

2.5

0.35

450

20

28,571.4

Movie Sound - Lesson 3 - Sound barrier 2.flv


Movie Sound - Lesson 3 - Sound barrier.flv















Science Bingo Starter or Plenary


Science Bingo • Draw a 3x3 grid.

• Write in 9 of the key words.

• If the clue matches your key word, cross it off.

• Once you have crossed off all key words shout “bingo!”

• If two people complete their grid at the same time, the winner will be the one with the most star words.


Key Words Frequency

The number of waves each second.

Amplitude Half the height of a wave

Oscilloscope An instrument which shows a picture of a wave on a screen

Wavelength The distance between the top of one wave and the top of the

next.

Vibration Move backwards and

forwards

Intensity The loudness or volume of a

sound.

Vacuum A completely empty space

with no particles.

Wave A way of transferring energy.

Gas Sound travels slowest through

this

Noise Unpleasant sound

Pitch How high or low a note

sounds.

Solid Sound travels fastest

through this

Pitch How high or low a note

sounds.

Impulse Electrical signal carried by a

nerve cell.

Threshold of hearing

The quietest sound that can be heard.

Volume How loud a sound is

Sound intensity meter

An instrument which measures the loudness of sound.

Eardrum A thin membrane inside the

ear which vibrates when sound reaches it.

Cochlea The part of the ear that changes vibrations into

electrical impulses.

Ultrasound Animals use this to hear

Decibel Unit for measuring the

loudness of a sound.

Noise Pollution

Constant unpleasant sound

Rarefaction Area of low pressure in a

sound wave.

Hertz The unit for frequency


Task: • Create an instruction booklet for novice-

spies on how to communicate using light and sound

OR

• A script for a children’s television programme about sound and light


Speed of sound - WordPress.com · 2016-01-25 · Sound in different materials Which state of matter...

Documents

Transcript of Speed of sound - WordPress.com · 2016-01-25 · Sound in different materials Which state of matter...