Kinematics: Study Guide

This guide covers sub-topic A.1, Kinematics, from Topic A, Space, Time and Motion, of IB Diploma Programme Physics, first assessment 2025. Like A.2, this sub-topic has no additional higher level (AHL) extension – the syllabus specifies identical content for both Standard Level and Higher Level students.

Where this fits in DP Physics

Kinematics is the first sub-topic of Theme A, Space, Time and Motion, and it establishes the vocabulary – displacement, velocity, acceleration – that the rest of Theme A and later themes build on directly. A.2 Forces and momentum immediately extends kinematics by asking what causes acceleration, introducing Newton’s laws and momentum on top of the SUVAT toolkit covered here. Without a secure grip on the distinction between scalar and vector quantities established in kinematics, force and momentum calculations in A.2 become far harder, since forces and momentum are themselves vectors and inherit the same sign-convention discipline. For the full five-topic picture of the syllabus, see the IB DP Physics syllabus guide.

Syllabus coverage

IB DIPLOMA PROGRAMME PHYSICS – A.1 KINEMATICS (SL AND HL)

• Core quantities and the scalar/vector distinction: distance and speed (scalars); displacement, velocity and acceleration (vectors)
• The SUVAT equations for motion under constant acceleration: v = u + at; s = ut + ½at²; v² = u² + 2as; s = ½(u + v)t
• Interpreting displacement-time graphs (gradient = velocity) and velocity-time graphs (gradient = acceleration; area under the graph = displacement), including curved graphs indicating non-uniform motion
• Projectile motion, treating horizontal and vertical components as independent: constant horizontal velocity (ignoring air resistance) combined with vertical motion under uniform gravitational acceleration

Vectors versus scalars in practice

The distinction between vector and scalar quantities is not just definitional – it determines which equations you can use and how you must handle direction. A common error is substituting a distance or speed value (scalars) into a SUVAT equation, which strictly requires displacement and velocity (vectors). This matters especially in problems involving a change of direction: an object thrown upward and caught again has travelled a distance equal to twice its maximum height, but its displacement – if caught at the same point it was thrown from – is zero. Always identify which of the two the question is actually asking for before substituting into an equation.

Worked example: projectile motion

A ball is thrown horizontally from a cliff top at 12 m/s and lands 2.4 s later. Find the height of the cliff. Horizontal and vertical motion are independent, so only the vertical direction matters here, since the ball has no initial vertical velocity: using s = ut + ½at² with u = 0, s = 0 + ½ × 9.81 × 2.4² = ½ × 9.81 × 5.76 = 28.3 m. The horizontal speed (12 m/s) is irrelevant to this particular question – it would only be needed to find the horizontal distance travelled, a separate calculation using s = vt in the horizontal direction. Keeping the two directions in entirely separate working, rather than mixing values from one into the other’s equation, is the single most common source of error in this topic.

How to approach it

Before reaching for a SUVAT equation, confirm the question genuinely describes constant acceleration – these four equations only hold under that condition, and a curved velocity-time graph is the clearest sign that they cannot be applied directly. Practise reading both displacement-time and velocity-time graphs fluently, since gradient and area carry different physical meanings on each (gradient of a displacement-time graph gives velocity; gradient of a velocity-time graph gives acceleration, while its area gives displacement) and exam questions frequently test this distinction directly. For projectile motion, set up two entirely separate sets of working – horizontal and vertical – before combining any results, since mixing values between the two directions is the most common source of error at this level. Set a consistent positive direction before starting any problem involving vectors, and apply it throughout, since sign errors are a frequent and avoidable source of lost marks.

Common mistakes

Using distance or speed values in a SUVAT equation that requires displacement or velocity, losing sign and direction information in the process. Forgetting that the gradient of a velocity-time graph gives acceleration, not velocity. Treating projectile motion’s horizontal and vertical components as connected, when they must be solved independently. Applying the standard SUVAT equations to a velocity-time graph that is curved rather than straight, when curved velocity-time graphs indicate non-uniform acceleration that the constant-acceleration SUVAT equations cannot handle directly.

Quick revision checklist

• Confirm a scenario describes constant acceleration before applying a SUVAT equation.
• Practise reading gradient and area correctly from both displacement-time and velocity-time graphs.
• Set up horizontal and vertical working separately for every projectile motion problem, combining results only at the end.
• Fix a consistent positive direction at the start of any vector-based problem and apply it throughout.

Connecting kinematics to internal assessment

Because kinematics involves quantities that are straightforward to measure with common equipment (distance, time, and derived speed or acceleration), it is a frequent starting point for student-designed internal assessment investigations – for example, measuring the acceleration of a trolley on a ramp, or the time of flight and range of a projectile launched at different angles. When kinematics forms the basis of an investigation, applying the same scalar/vector discipline and SUVAT framework covered here to justify a chosen method, and to explain any systematic error introduced by how a quantity was measured (reaction-time error in manual timing, for instance), demonstrates exactly the kind of connection between taught content and independent investigation that a strong IA report draws on.

Official syllabus

International Baccalaureate Organization, Physics guide (Diploma Programme), first assessment 2025, sub-topic A.1. Overview at ibo.org – the same source already cited by the full syllabus guide and the revision notes already on the site. Verified 2026-09-06.