AQA · GCSE · Physics

    Course version: 8463 · Version from Sept 2016

    The velocity of an object is its speed in a given direction. Velocity is a…

    Full specification wording

    Velocity: The velocity of an object is its speed in a given direction. Velocity is a vector quantity.

    Because a direction is part of it, a velocity changes whenever either the speed or the direction changes.

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

    • Point 1 of 3
    • 4 key terms

    Study notes

    From the checked teaching notes for this specification point.

    The idea

    Because a direction is part of it, a velocity changes whenever either the speed or the direction changes. A car driving round a bend at a steady 13 m/s has a constant speed but a changing velocity, and average-speed cameras can only report a speed, since the road between them is not straight. Constant velocity therefore means moving in a straight line at a steady rate, and anything else is accelerating. On a straight road, opposite directions are handled with signs, so a vehicle travelling at 20 m/s that turns round and comes back at 20 m/s has changed its velocity by 40 m/s. Velocity is measured in metres per second, exactly like speed, so the unit alone never tells you which quantity you are holding.

    What earns the marks

    • Velocity as a speed in a given direction.
    • Velocity as a vector and speed as a scalar.
    • A change of direction counting as a change of velocity.
    • Constant velocity requiring motion in a straight line at a steady speed.

    Common mistakes and how to put them right

    • Saying velocity and speed are the same because they share a unit.

    • Claiming a car on a bend at a steady rate has constant velocity.

    • Giving a velocity with no direction.

    • Asserting that a changing velocity always means a changing speed.

    Exam tips

    • If the path is not straight, the velocity is changing; say so explicitly.
    • Quote both the magnitude and the direction whenever a velocity is asked for.

    Try the lesson

    The start of the Velocity: The velocity of an object is its speed in a given direction. Velocity is a vector quantity. lesson, made from checked teaching notes for this specification point.

    Have a go first

    A car is travelling at 15 m/s due north. Which statement describes the velocity of the car?

    Listen

    Because a direction is part of it, a velocity changes whenever either the speed or the direction changes. A car driving round a bend at a steady 13 m/s has a constant speed but a changing velocity, and average-speed cameras can only report a speed, since the road between them is not straight. Constant velocity therefore means moving in a straight line at a steady rate, and anything else is accelerating. On a straight road, opposite directions are handled with signs, so a vehicle travelling at 20 m/s that turns round and comes back at 20 m/s has changed its velocity by 40 m/s. Velocity is measured in metres per second, exactly like speed, so the unit alone never tells you which quantity you are holding. A strong answer earns marks for these points. velocity as a speed in a given direction. velocity as a vector and speed as a scalar. a change of direction counting as a change of velocity. constant velocity requiring motion in a straight line at a steady speed. Exam tip: If the path is not straight, the velocity is changing; say so explicitly.

    See it

    A top-down flowchart. The top node reads 'Velocity: speed in a given direction'. Four arrows lead from it to: 'Vector quantity'; 'Measured in metres per second, like speed'; 'Velocity changes if speed changes'; and 'Velocity changes if direction changes'. From 'Velocity changes if direction changes' an arrow leads to 'Car on a bend at steady speed: constant speed, changing velocity'. Both 'Velocity changes if speed changes' and 'Velocity changes if direction changes' lead to 'Constant velocity: straight line at a steady rate', which leads to 'Anything else is accelerating'.
    It shows that velocity is speed in a given direction, that it changes if either speed or direction changes, and what constant velocity requires.

    Key words

    Say what each word means before you turn the card.

    velocity

    Try answering aloud or in your head before turning the card.

    constant velocity

    Try answering aloud or in your head before turning the card.

    changing direction

    Try answering aloud or in your head before turning the card.

    sign conventions

    Try answering aloud or in your head before turning the card.

    See every definition
    velocity
    The speed of an object in a given direction, and a vector quantity.
    constant velocity
    Moving in a straight line at a steady rate.
    changing direction
    A change of direction counts as a change of velocity.
    sign conventions
    On a straight road, opposite directions are handled with signs.

    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 'Velocity: speed in a given direction'. Four arrows lead from it to: 'Vector quantity'; 'Measured in metres per second, like speed'; 'Velocity changes if speed changes'; and 'Velocity changes if direction changes'. From 'Velocity changes if direction changes' an arrow leads to 'Car on a bend at steady speed: constant speed, changing velocity'. Both 'Velocity changes if speed changes' and 'Velocity changes if direction changes' lead to 'Constant velocity: straight line at a steady rate', which leads to 'Anything else is accelerating'.

    • 1Box 1

    • 2Box 2

    • 3Box 3

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