Velocity-time graphs

• Velocity means speed in a certain direction

• A velocity-time graph is sometimes called a speed-time graph

• You need to be able to interpret a velocity-time graph

• Use the two golden rules on the right to answer questions involving speed, time and acceleration

Golden rules

• The gradient of a velocity-time graph tells you the acceleration

• The most common units of acceleration are m/s(2)

  • Acceleration = change in velocity / change in time

• The area underneath a velocity-time graph tells you the distance travelled

  • If you have to estimate the area under a curve use the techniques shown later

Problem solved

• The easiest way to solve this problem is to sketch a velocity-time graph of a journey

• The graph doesn’t have to be to scale, but make sure you label the axes and mark any important points

• Constant deceleration means that this section of the velocity-time graph will be a straight line

• To calculate the total distance travelled you need to work out the total area underneath the graph

• Divide it into sections, work out the area of each section, and then add them together