Unit Overview

Kinematics

CIE A-Level Physics· 5 min read 📊 n/a

1. Unit at a glance

Kinematics is the study of how objects move, without yet considering the forces that cause motion. We start by defining key quantities, then build up to solving problems for straight-line motion and curved projectile motion.

This learning path progresses from foundational definitions to practical problem solving, with graphical methods building intuition before we introduce algebraic equations for accelerated motion.

This unit is split into the following sub-topics:

Distance, displacement, speed, velocity and acceleration

Distinguishes scalar vs vector quantities and defines core kinematic terms for motion.

★⏱ 10 min

Graphical representation of motion

Teaches how to interpret and draw displacement-time and velocity-time graphs for motion.

★★⏱ 12 min

Uniformly accelerated motion equations

Derives and applies the 4 suvat equations for motion with constant acceleration.

★★★⏱ 15 min

Free fall

Analyzes motion of objects accelerating under gravity only, including experimental methods.

★★⏱ 10 min

Projectile motion

Resolves projectile motion into horizontal and vertical components to solve trajectory problems.

★★★★⏱ 15 min

2. Common Pitfalls

Wrong move:

Mixing up scalar (distance/speed) and vector (displacement/velocity) quantities in calculations

Why:

This leads to incorrect signs and wrong final answers, especially for motion that changes direction

Correct move:

Always confirm whether a question asks for scalar or vector values, and assign signs correctly based on your reference direction

Wrong move:

Using suvat equations for motion with non-uniform acceleration

Why:

The suvat equations are only derived for constant acceleration, so they give incorrect results for changing acceleration

Correct move:

Use graphical methods to solve problems involving non-uniform acceleration in this syllabus

Wrong move:

Treating horizontal acceleration as non-zero for standard projectile motion

Why:

Ignoring the standard assumption of negligible air resistance leads to incorrect trajectory calculations

Correct move:

Always assume $a_{x} = 0$ for horizontal projectile motion, unless the question explicitly states otherwise

3. Quick Reference Cheatsheet

Concept	Key Formula/Rule
Average speed	$v_{a v} = \frac{total distance}{total time}$
Gradient of displacement-time graph	Equal to velocity
Area under velocity-time graph	Equal to displacement
Gradient of velocity-time graph	Equal to acceleration
SUVAT equations (constant $a$ )	$v = u + a t$ , $s = u t + \frac{1}{2} a t^{2}$ , $v^{2} = u^{2} + 2 a s$ , $s = \frac{( u + v )}{2} t$
Free fall acceleration	$a = g = 9.81 m s^{- 2}$ downwards
Projectile horizontal motion	$a_{x} = 0$ , $v_{x} = u_{x} = constant$
Projectile vertical motion	$a_{y} = g$ , follows uniform acceleration rules

What's Next

Begin your study of this kinematics unit with the first sub-topic, which introduces the core scalar and vector definitions you will rely on for all subsequent topics in mechanics. After completing all sub-topics in this unit, you will progress to Unit 3: Dynamics, which builds on kinematic concepts to explain how forces cause changes in motion.