AQA · GCSE · Physics

    Course version: 8463 · Version from Sept 2016

    It is not only moving objects that have varying speed. The speed of sound…

    Full specification wording

    Speed: It is not only moving objects that have varying speed. The speed of sound and the speed of the wind also vary.

    The speed of sound is a property of the material the wave travels through rather than of the source, and it changes when the material changes: about 330 m/s in air, roughly 1500 m/s in water and…

    Checked against the AQA 8463 specification (opens in a new tab) on .

    • Point 6 of 9

    Study notes

    From the checked teaching notes for this specification point.

    The idea

    The speed of sound is a property of the material the wave travels through rather than of the source, and it changes when the material changes: about 330 m/s in air, roughly 1500 m/s in water and around 5000 m/s in steel, because particles that are closer together pass the vibration on faster. Warmer air also carries sound a little faster, so the figure for air is only a typical one. Wind speed varies constantly with the weather, with height above the ground and with the shelter of buildings and hills, which is why wind turbines are mounted on tall towers in exposed places. In both cases a single quoted number is an average or a typical figure and not a fixed constant of nature.

    What earns the marks

    • The speed of sound depending on the medium it travels through.
    • Sound travelling faster in solids than in gases, with closer particles as the reason.
    • The speed of sound in air changing with temperature.
    • Wind speed varying with the weather, the height or the surroundings.

    Common mistakes and how to put them right

    • Believing a loud sound travels faster than a quiet one.

    • Quoting the speed of sound in air for a sound travelling through water or metal.

    • Saying sound travels fastest in a vacuum.

    • Treating 330 m/s as an exact value under all conditions.

    Exam tips

    • Check the medium before choosing a value for the speed of sound.
    • Use 330 m/s for air unless the question supplies a different figure.

    Try the lesson

    The start of the Speed: It is not only moving objects that have varying speed. The speed of sound and the speed of the wind also vary. lesson, made from checked teaching notes for this specification point.

    Have a go first

    Which of the following statements about the speed of sound and the speed of the wind is correct?

    Listen

    The speed of sound is a property of the material the wave travels through rather than of the source, and it changes when the material changes: about 330 m/s in air, roughly 1500 m/s in water and around 5000 m/s in steel, because particles that are closer together pass the vibration on faster. Warmer air also carries sound a little faster, so the figure for air is only a typical one. Wind speed varies constantly with the weather, with height above the ground and with the shelter of buildings and hills, which is why wind turbines are mounted on tall towers in exposed places. In both cases a single quoted number is an average or a typical figure and not a fixed constant of nature. A strong answer earns marks for these points. the speed of sound depending on the medium it travels through. sound travelling faster in solids than in gases, with closer particles as the reason. the speed of sound in air changing with temperature. wind speed varying with the weather, the height or the surroundings. Exam tip: Check the medium before choosing a value for the speed of sound.

    See it

    A top-down flowchart. The top node reads 'Speed of sound depends on the medium' and branches to three nodes: 'Air: about 330 m/s', 'Water: roughly 1500 m/s' and 'Steel: around 5000 m/s'. The steel node leads to 'Particles closer together pass the vibration on faster'. The air node leads to 'Warmer air carries sound a little faster', which leads to 'Figure for air is only a typical one'. A separate node 'Wind speed varies' branches to three nodes: 'With the weather', 'With height above the ground' and 'With shelter of buildings and hills'.
    Shows that the speed of sound depends on the medium and that wind speed varies with the weather, height and surroundings.

    Label the diagram

    Some boxes have lost their names. Pick the right name for each number.

    The diagram again, with 3 boxes numbered instead of named. A top-down flowchart. The top node reads 'Speed of sound depends on the medium' and branches to three nodes: 'Air: about 330 m/s', 'Water: roughly 1500 m/s' and 'Steel: around 5000 m/s'. The steel node leads to 'Particles closer together pass the vibration on faster'. The air node leads to 'Warmer air carries sound a little faster', which leads to 'Figure for air is only a typical one'. A separate node 'Wind speed varies' branches to three nodes: 'With the weather', 'With height above the ground' and 'With shelter of buildings and hills'.

    • 1Box 1

    • 2Box 2

    • 3Box 3

    0 of 3 labelled

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