Cambridge IGCSE Physics 0625
1.0 Motion, forces and energy
Chapter overview and direct access to all eight topics.
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Table of contents
Select a topic to open its complete Core and Extended notes, equations, examples, questions and flashcards.
- 1.1 Physical quantities and measurement techniquesLength, volume, time, averages, scalars, vectors and vector resultants
- 1.2 MotionSpeed, velocity, acceleration, graphs, free fall and terminal velocity
- 1.3 Mass and weightQuantity of matter, gravitational force and gravitational field strength
- 1.4 DensityMass per unit volume, practical measurements, floating and sinking
- 1.5 ForcesEffects of forces, friction, springs, moments, equilibrium and centre of gravity
- 1.6 MomentumMomentum, impulse, conservation and force as a rate of momentum change Extended
- 1.7 Energy, work and powerEnergy stores, transfers, resources, efficiency, work and power
- 1.8 PressureForce per unit area and pressure changes beneath liquid surfaces
Chapter overview
What this chapter is about
This chapter develops the language and calculations used to describe objects, their motion and the interactions that change that motion. It begins with accurate measurement because every later conclusion depends on reliable values and correctly stated units.
Motion is described using distance, speed, time, velocity and acceleration. Distance–time and speed–time graphs then provide visual ways to interpret movement and calculate quantities such as speed, acceleration and distance travelled.
Mass, weight and density describe important properties of objects and materials. Mass measures the quantity of matter, weight is a gravitational force, and density compares mass with volume.
Forces explain changes in speed, direction and shape. The chapter includes friction and drag, spring behaviour, resultant forces, circular motion, moments, equilibrium and centre of gravity.
Momentum and energy provide two powerful conservation principles. Momentum is especially useful for collisions, while energy stores and transfers connect motion, forces, work, power, efficiency and energy resources.
The final topic introduces pressure. Pressure links a force to the area over which it acts and explains both solid-contact examples and the increase in pressure beneath a liquid surface.
Big-picture understanding
How the topics connect
Measurement supports every topic
Length and time measurements are used to calculate speed. Mass and volume measurements give density. Force, area and depth measurements are needed for pressure. Correct units and sensible precision matter throughout.
Vectors carry direction
Velocity, acceleration, force and momentum are vectors. Direction signs are essential when resolving forces or solving one-dimensional momentum problems.
Graphs turn data into meaning
The gradient of a distance–time graph gives speed, while the gradient of a speed–time graph gives acceleration. The area beneath a speed–time graph gives distance travelled.
Forces link motion and energy
A resultant force can accelerate an object and change its momentum. When a force moves an object, work is done and energy is transferred.
Conservation solves changes
Momentum is conserved in a closed system with no resultant external force. Energy cannot be created or destroyed, although it may be dissipated to less useful stores.
Properties affect outcomes
Mass affects inertia, weight, momentum and kinetic energy. Density affects floating and liquid pressure. Contact area determines the pressure produced by a force.
Quick reference
Chapter equation map
Use this map for orientation. Each linked topic page explains the symbols, units, rearrangements and worked examples in full.
| Topic | Key equations | Level |
|---|---|---|
| 1.2 Motion | v = s ÷ t; average speed = total distance ÷ total time; a = Δv ÷ Δt | Core + Extended |
| 1.3 Mass and weight | g = W ÷ m; W = mg | Core + Extended |
| 1.4 Density | ρ = m ÷ V | Core |
| 1.5 Forces | moment = force × perpendicular distance; k = F ÷ x; F = ma | Core + Extended |
| 1.6 Momentum | p = mv; impulse = FΔt = Δ(mv); F = Δp ÷ Δt | Extended |
| 1.7 Energy, work and power | W = Fd = ΔE; P = W ÷ t; Ek = 0.5mv2; ΔEp = mgΔh | Core + Extended |
| 1.8 Pressure | p = F ÷ A; Δp = ρgΔh | Core + Extended |
Recommended order
How to study this chapter
- 1Build the measurement foundation
Start with Topic 1.1. Practise reading instruments, using SI units and distinguishing scalars from vectors.
- 2Master motion and graphs
Study Topic 1.2 and practise gradients, areas beneath graphs and descriptions of acceleration.
- 3Connect matter to forces
Study mass, weight and density before the larger forces topic. This makes gravitational and material examples easier to interpret.
- 4Apply conservation principles
Use momentum and energy to solve events involving collisions, falling objects, machines and transfers.
- 5Finish with pressure
Combine force, area, density and depth in the final topic, then return to mixed Chapter 1 questions.