Velocity and Acceleration

This lesson covers the difference between velocity and speed, the acceleration equation, velocity–time graphs and the area-under-the-graph method, as required by the Edexcel GCSE Combined Science specification (1SC0). Understanding acceleration is essential for analysing motion.

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Velocity vs Speed

• Speed is a scalar — it has magnitude only. It tells you how fast an object is moving.
• Velocity is a vector — it has magnitude and direction.

An object moving at constant speed in a circle has a changing velocity because its direction is constantly changing, even though its speed stays the same.

Quantity	Type	Includes Direction?
Speed	Scalar	No
Velocity	Vector	Yes

Example

A car travelling at 20 m/s due north has:

• A speed of 20 m/s
• A velocity of 20 m/s north

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Acceleration

Acceleration is the rate of change of velocity. It is a vector quantity.

$a = \frac{\Delta v}{\Delta t} = \frac{v - u}{t}$a=ΔtΔv​=tv−u​

where:

• a = acceleration (m/s²)
• v = final velocity (m/s)
• u = initial velocity (m/s)
• t = time taken (s)