GCSEPhysics: Combined ScienceAQARevision Notes5. Forces5.4 Describing Motion5.4.2 Speed

Speed (AQA GCSE Physics: Combined Science)

Revision Note

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Speed

  • The speed of an object is the distance it travels every second
  • Speed is a scalar quantity
    • This is because it only contains a magnitude (without a direction)

  • The average speed of an object is given by the equation:

  • Distance is measured in metres, m
  • Time is measured in seconds, s
    • Speed is therefore measured in metres per second, m/s

Person vs Bee, downloadable IGCSE & GCSE Physics revision notes

A hiker might have an average speed of 2.0 m/s, whereas a particularly excited bumble bee can have average speeds of up to 4.5 m/s

Examiner Tip

Remember that average speed is the mean speed of the moving object.Its speed at a specific moment could be higher or lower - so because the speed changes you need to consider the total distance and time taken.

Non-Uniform Motion

  • The speed of an object is rarely constant
    • Hikers change their pace continuously as they walk
    • Bumblebees buzz around in all directions with varying speed
    • Cars are constantly speeding up and slowing down throughout a journey

  • Non-uniform motion refers to motion that is changing
  • Changing motion can mean the object is changing its speed, direction or both

Non-Uniform Speed, downloadable IGCSE & GCSE Physics revision notes

Race drivers know all about non-uniform motion, especially slowing down for corners and speeding up on the straight sections of track

Katie M, Physics

Teacher tip

Katie M

Physics

In my experience of teaching, non-uniform motion is one of those phrases in physics that sounds much more complicated than it actually is, and students can initially be a bit intimidated by it. When we met phrases like this, I would get them to explain the meaning of each word individually. What does uniform mean? The same. Great, so what does non-uniform mean? Not the same. Fantastic. So non-uniform motion is just motion that doesn’t stay the same, in other words, motion that changes. This is a great technique to use for unfamiliar words and phrases, in all subjects. But especially in the sciences where there is a lot of specialist terminology that can sound very intimidating.

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    Katie M

    Author: Katie M

    Expertise: Physics

    Katie has always been passionate about the sciences, and completed a degree in Astrophysics at Sheffield University. She decided that she wanted to inspire other young people, so moved to Bristol to complete a PGCE in Secondary Science. She particularly loves creating fun and absorbing materials to help students achieve their exam potential.