Kinematics: Uniform Acceleration

Kinematics is the branch of mechanics that describes motion without worrying about what causes it. Before we can understand forces and Newton's laws, we need a solid grasp of how objects move — and the mathematical tools to describe that motion precisely.

In this lesson, we focus on uniformly accelerated motion in a straight line — the foundation of almost every mechanics problem at A-Level.

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Key Definitions

Displacement (s) — the distance moved in a particular direction from a reference point. A vector quantity, measured in metres (m).

Velocity (v) — the rate of change of displacement. A vector quantity, measured in m/s.

Average velocity = total displacement / total time

Acceleration (a) — the rate of change of velocity. A vector quantity, measured in m/s².

Average acceleration = change in velocity / time taken = (v - u) / t

When acceleration is uniform (constant), we can use a special set of equations to solve problems.

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The SUVAT Equations

For motion with constant acceleration in a straight line, five quantities are related by four equations. The five quantities are: