Instantaneous Speed (AQA GCSE Physics)

Instantaneous Speed

• If an object’s speed is changing, then its distance-time graph will be a curve

  • If it’s accelerating (speeding up), then the line will curve upwards

  • If it’s decelerating (slowing down), then the line will curve downwards

• The speed at a particular time is found by calculating the gradient of a tangent to the curve, as shown in the image below:

Tangents are used to calculate the gradient at specific points on curved lines. On a distance-time graph, the gradient represents the speed of a moving object

• The tangent is a straight line that touches the curve at a particular point

  • This point will be the time at which the speed is to be found

• The gradient of the tangent is then found from the same gradient equation: