GCSE Physics · Edexcel 1PH0 · Topic 2A
Speed, velocity and acceleration
Key points
- Speed is distance travelled per unit time: . Velocity is speed in a stated direction, so it is a vector.
- Acceleration is the rate of change of velocity: , measured in m/s². A negative value means slowing down (deceleration).
- For uniform acceleration use (given on the equation sheet).
- On a distance–time graph the gradient is the speed; a flat line means stationary and a curve means changing speed.
- On a velocity–time graph the gradient is the acceleration and the area under the graph is the distance travelled.
- Typical speeds: walking about 1.5 m/s, cycling about 6 m/s, a car on a motorway about 30 m/s. Objects falling freely near Earth accelerate at about 10 m/s².
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Before you can explain motion you need to describe it precisely. This sub-topic covers the difference between speed and velocity, how to calculate acceleration, and how to read the two main motion graphs.
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