A.1.7—Uniform vs non-uniform acceleration

Uniform acceleration

Acceleration is uniform when the velocity changes by equal amounts in equal time intervals. The velocity–time graph is a straight line with constant gradient.

Non-uniform acceleration

Acceleration is non-uniform when its magnitude or direction changes. The velocity–time graph then has a changing gradient, and a single SUVAT value cannot describe the entire interval.

Model versus reality

A constant-acceleration model can be useful over a limited interval even when real forces vary. State the approximation and identify the neglected force or changing condition.

Common trap

A curved trajectory does not by itself prove that acceleration is non-uniform: projectile motion without drag has constant downward acceleration while its velocity direction changes.

How it is assessed

The evidence asks for one reason a spacecraft’s acceleration is not constant and one reason a dancer model is unrealistic, rewarding a specific neglected or changing physical parameter.

Command terms

State / Outline

What earns marks

Give a physical reason why acceleration changes: for example, a changing force, changing radiation intensity, changing force direction, drag, or an omitted interaction. Link the reason to the acceleration rather than merely saying the motion is unrealistic.

Watch for

Giving a vague statement such as “the model is not realistic” without naming a force, changing condition, or neglected parameter.

Representative question

[Maximum number: 1]

State one reason why the acceleration of the spacecraft will not be constant.

A.1.7—Uniform vs non-uniform acceleration

Recognize Uniform and Non-Uniform Acceleration

A.1.7 Exam Analysis

Assessment in practice

Question 1