What are speed, velocity and acceleration?

Speed, velocity and acceleration: a = Δv ÷ Δt. Speed is how far you go each second. Velocity is speed with a direction, and acceleration is how quickly the velocity changes: speeding up, slowing down or turning. Speed is distance ÷ time, in m/s (1 m/s = 3.6 km/h).

Read how it works: What are speed, velocity and acceleration? · The history of speed, velocity and acceleration · More boxes on Glassbox

Chapters in this interactive model

1. How fast, which way, and how quickly it changes: Speed, velocity and acceleration, on a straight road with a stopwatch.
2. Nought to a hundred: A drag race: how quickly a car, an EV, a motorbike and a bicycle gain speed.
3. Slowing down, stopping and falling: Stopping distances, school zones, a dropped ball and the g-force in a lift.
4. Going round, and what the needle shows: Steady speed can still be acceleration. And average speed is not the speed right now.
5. Speed is not velocity, and other surprises: A lap that goes nowhere, a myth about falling, and why nothing catches light.