• Speed (ms^-1)= Distance/ Time
• A distance-time graph can make it easier to represent motion
• A velocity (speed in a given direction) – time graph can show the instantaneous speed

• DISTANCE – the length of the path you have taken
• DISPLACEMENT – the straight line distance between two places 
• To describe displacement, you need to say how far you are away from the start and 
  • Scalar – only size or magnitude
  • Vector quantity – size and direction

• Acceleration is the rate of change of velocity with time, so it is also a vector. Acceleration happens when there is:
  • A change in SPEED, or
  • A change in DIRECTION, or
  • A change in speed AND direction
• If an objects speed is constant but its velocity is changing, we say it is also accelerating

• With a train travelling at a constant speed in a circle, it is considered to be accelerating but its average velocity as it goes round the track back to its starting point is zero, as its DISPLACEMENT is ZERO

• When something decelerates, it is negative acceleration, so -1 ms-2 A straight line on a velocity time graph is UNIFORM acceleration

ACCELERATION – the rate of change of velocity with time

The graph shows the motion of a ball being thrown up in the air, falling, and then being caught.

• A – The ball is at rest
• A to D – the ball is thrown up with a uniform upward acceleration
• D to B – it has a negative acceleration as the ball accelerates downwards until resting at B
• B to E – the same velocity as D to B but it is negative as it accelerates down
• E – The ball is caught and brought to rest by C

Non-linear graphs (curved graphs) – make strips/rectangles under the graph, calculate the area and add it up

'this is less accurate than a linear graph'

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