Edexcel A-Level Maths: Mechanics — Complete Revision Guide (9MA0 Paper 3)
Edexcel A-Level Maths: Mechanics — Complete Revision Guide (9MA0 Paper 3)
Mechanics is the half of Edexcel A-Level Maths Paper 3 that often feels the most foreign at first, and the most rewarding once it clicks. It is where the pure mathematics you have practised — calculus, vectors, trigonometry, algebra — gets pointed at physical situations: a particle sliding down a slope, two masses connected over a pulley, a projectile launched at an angle, a beam balanced on a support. The maths is not new. The discipline of choosing the right model, drawing a clean force diagram, and resolving in sensible directions is.
This guide is a topic-by-topic walkthrough of the mechanics content in the 9MA0 specification. For each topic you will see the core skills, the typical pitfalls, a short worked example, and a link to the full lesson on the LearningBro course. The aim is not to replace working through past papers — the only way to get good at mechanics is to do dozens of full questions, force diagrams and all. The aim is to give you a clear map of what you need to know, in the order Edexcel teaches it, so your revision is targeted rather than scattered.
What the Edexcel 9MA0 Specification Covers
The Edexcel A-Level Maths qualification (9MA0) is assessed through three two-hour papers, each worth 100 marks. Papers 1 and 2 cover pure mathematics. Paper 3 is split: Section A is statistics, Section B is mechanics, with roughly 50 marks each. Mechanics therefore carries about a sixth of the whole A-Level, and the questions tend to be longer and more structured than pure questions — multi-part, with clear method marks for each stage of the argument.
Mechanics on 9MA0 sits in Section 8 of the overall specification. The conventional value g=9.8 m/s2 is used throughout unless a question states otherwise, and standard modelling assumptions — particles treated as points, strings as light and inextensible, pulleys as smooth, surfaces as smooth or rough — are assumed unless told otherwise. The table below shows the sub-topics, the part of the specification they sit under, and a realistic estimate of how the 50 marks of Paper 3 Section B typically distribute.
| Topic | Spec Section | Typical Paper 3B marks weight |
|---|---|---|
| Kinematics with constant acceleration | 8.1 | 6-10 marks |
| Kinematics with variable acceleration (calculus) | 8.2 | 6-8 marks |
| Forces and Newton's laws | 8.3 | 6-10 marks |
| Connected particles and pulleys | 8.3 | 6-8 marks |
| Moments | 8.4 | 5-8 marks |
| Vectors in mechanics | 8.5 | 4-6 marks |
| Projectile motion | 8.6 | 6-10 marks |
| Friction | 8.7 | 4-6 marks |
| Statics and equilibrium | 8.8 | 4-8 marks |
| Applications and modelling | 8.9 | spread across all topics |
These weights are estimates based on the spread of typical 9MA0 papers — not guarantees for any single year. What is reliable, however, is that Paper 3 Section B almost always contains one extended kinematics or projectile question, one connected-particles or pulley question, and one moments or equilibrium question, with vectors and friction often woven into the others. Mastering the standard question shapes is high-leverage revision.
Kinematics with Constant Acceleration
Kinematics is the description of motion without yet asking what causes it. With constant acceleration in a straight line, the whole topic reduces to five quantities — displacement s, initial velocity u, final velocity v, acceleration a and time t — and the suvat equations that link them: v=u+at, s=ut+21at2, s=21(u+v)t, v2=u2+2as and s=vt−21at2. Each equation contains four of the five quantities. The question tells you three and asks for one; choose the equation that contains your three knowns and the one unknown, and avoid the one containing the quantity you do not need.
The other essential tool is the velocity-time graph. The gradient is the acceleration; the area under it is the displacement. Many Edexcel questions reduce to splitting the area into triangles and trapeziums. For motion under gravity, take downward as positive (or upward; just be consistent) and use a=g=9.8 m/s2 in the chosen direction.
A common pitfall is mixing sign conventions partway through a question. If you choose upward as positive, then g must be entered as −9.8 in every suvat equation, and an upward velocity is positive throughout. Switching mid-problem is the single biggest source of lost marks in vertical-motion questions. Another pitfall is using suvat when the acceleration is not constant — these equations are only valid when a is constant.
A short worked example. A ball is thrown vertically upwards from ground level at 14 m/s. Taking upward as positive, u=14, a=−9.8. At the highest point v=0, so 0=14−9.8t gives t≈1.43 s. The maximum height comes from v2=u2+2as: 0=196−19.6s, so s=10.0 m to 3 s.f.
For full coverage with practice questions and worked solutions, see the Kinematics: Constant Acceleration lesson.
Kinematics with Variable Acceleration
When acceleration varies with time, the suvat equations no longer apply and you must use calculus. The relationships are simple to state: differentiating displacement with respect to time gives velocity, and differentiating velocity gives acceleration. Integrating reverses the chain. So v=dtds, a=dtdv=dt2d2s, and s=∫vdt, v=∫adt.
The standard workflow is to identify which quantity you have been given as a function of t and which one you need, then differentiate or integrate as required. Constants of integration matter — they are usually fixed by an initial condition such as "the particle starts from rest at the origin" giving v(0)=0 or s(0)=0. Forgetting to find C is one of the most common ways to lose method marks here.
A short worked example. A particle moves along a straight line so that its velocity at time t seconds is v=3t2−12t+9 m/s for t≥0. Find the times at which it is instantaneously at rest, and its displacement from the start at t=4.
Setting v=0: 3t2−12t+9=0, so t2−4t+3=0, giving t=1 or t=3. Integrating, s=t3−6t2+9t+C. Taking s(0)=0, we find C=0, so at t=4, s=64−96+36=4 m.
A common pitfall is confusing distance with displacement when the particle changes direction. Displacement at t=4 is 4 m; total distance travelled is s(1)−s(0)+∣s(3)−s(1)∣+s(4)−s(3) and is larger. Edexcel questions often ask for one or the other specifically, and writing the wrong quantity costs the final mark even when the calculus is correct.
For worked examples on differentiating and integrating motion, including distance-versus-displacement problems, see the Kinematics: Variable Acceleration lesson.
Forces and Newton's Laws
Once you know how a particle moves, the next question is what causes it to move that way. Newton's second law, F=ma, is the central equation of mechanics. Almost every mechanics question on 9MA0 reduces, somewhere, to applying F=ma to a clearly drawn free-body diagram.
The skill that makes mechanics work is drawing force diagrams properly. For each particle, draw an arrow for every force acting on it — weight mg downward, normal reaction R perpendicular to any surface, tension T along any string, friction F opposing motion, applied force as given. Resolve along sensible axes — usually horizontal/vertical for level motion, or parallel/perpendicular to the slope for inclined motion. Apply F=ma in each direction independently.
A short worked example. A box of mass 5 kg is pulled along a smooth horizontal floor by a horizontal force of 20 N. Vertically, R=mg=49 N. Horizontally, F=ma gives 20=5a, so a=4 m/s2.
A common pitfall is forgetting that weight is mg, not m — convert mass to a force using g=9.8 m/s2. Another is mixing magnitude and direction; F=ma is a vector equation. A third is dropping the normal reaction on inclined planes — on a slope, R=mgcosθ, not mg.
For force-diagram practice and worked F=ma problems on horizontal, vertical and inclined motion, see the Forces and Newton's Laws lesson.
Connected Particles and Pulleys
A connected-particle problem is one in which two or more bodies move together because they are joined by a string, rod or contact. Provided the string is light and inextensible, both particles share the same magnitude of acceleration and the tension is the same throughout the string. For a smooth pulley, the string changes direction without losing tension, so the tension is identical on each side.
The workflow is to draw a separate force diagram for each particle, write F=ma for each particle in the direction of its motion, and solve the resulting simultaneous equations for the two unknowns (typically the acceleration a and the tension T).
A short worked example. Two particles, masses 3 kg and 5 kg, are connected by a light inextensible string over a smooth pulley and released from rest. For the heavier particle (descending): 5g−T=5a. For the lighter particle (ascending): T−3g=3a. Adding gives 2g=8a, so a=g/4=2.45 m/s2. Then T=3g(5/4)=36.75 N.
A common pitfall is signing the acceleration inconsistently. Set up each equation in the direction the particle actually moves so a comes out as the same positive number in both. A second pitfall is forgetting to convert mass to weight; a third is missing a force on one of the diagrams (usually the tension).
For pulley problems with two particles, particle-on-table-with-hanging-mass set-ups, and connected particles on slopes, see the Connected Particles and Pulleys lesson.
Moments
A moment is the turning effect of a force about a point. The moment of a force of magnitude F about a point, when the perpendicular distance from the point to the line of action is d, is Fd. Units are newton-metres (N m). Moments are signed; declare your sign convention at the start.
For a body in rotational equilibrium, the total moment about any point is zero. Combined with translational equilibrium (∑F=0), this lets you solve problems with several unknown forces by taking moments about a point that eliminates an unknown from the equation.
The classic Edexcel question is a uniform beam on two supports, with weights placed on it. "Uniform" means the weight acts at the midpoint. Vertical equilibrium gives R1+R2= total weight; taking moments about one support eliminates the corresponding R and lets you solve directly for the other.
A short worked example. A uniform beam of length 4 m and mass 20 kg rests horizontally on supports at each end. A weight of 50 N sits 1 m from the left end. The beam's weight is 20g=196 N acting at the centre. Moments about the left support: R2×4=50×1+196×2, so R2=110.5 N. Then R1=246−110.5=135.5 N.
A common pitfall is using the wrong distance — moments use the perpendicular distance from the pivot to the line of action. For a non-uniform beam the centre of mass is given to you and is not the midpoint. A third is choosing a poor pivot; pick one where unknowns vanish.
For beam-on-supports problems, including non-uniform beams and tipping-point questions, see the Moments lesson.
Vectors in Mechanics
Vectors in mechanics applies the i, j notation from pure to displacement, velocity, acceleration and force in two dimensions. The pure-side rules — adding components, magnitude ∣a∣=a12+a22, direction by arctan — carry over unchanged.
The new content is vector kinematics with constant acceleration: v=u+at and r=r0+ut+21at2. Each component obeys the scalar suvat equations independently, so a particle's x-motion and y-motion can be analysed separately and combined at the end. For variable acceleration, the rules are the same applied componentwise: v=dtdr and a=dtdv.
A short worked example. A particle has initial velocity u=(3i+4j) m/s and constant acceleration a=(i−2j) m/s2. At t=2, v=(3i+4j)+2(i−2j)=5i m/s, so ∣v∣=5 m/s.
A common pitfall is mixing scalar and vector reasoning — reporting the speed as u+at rather than ∣u+at∣. Another is confusing displacement (a vector) with distance (its magnitude).
For component-wise suvat practice and 2D vector kinematics problems, see the Vectors in Mechanics lesson.
Projectile Motion
Projectile motion is one of the highest-value topics on Paper 3 Section B and one of the most predictable in shape. A particle is launched into the air with some initial speed at some angle, and you are asked about its trajectory: the time of flight, the range, the maximum height, the speed and direction at a given time. Once gravity is the only force acting, the motion separates into two independent suvat problems — one horizontal, one vertical.
The setup is always the same. Launch speed u at angle θ above the horizontal. Resolve the initial velocity into components: horizontal ux=ucosθ, vertical uy=usinθ. Horizontally, there is no force (we ignore air resistance), so the horizontal velocity stays at ucosθ and the horizontal displacement after time t is x=ucosθ⋅t. Vertically, the only force is gravity, so a=−g, the vertical velocity is vy=usinθ−gt, and the vertical displacement is y=usinθ⋅t−21gt2.
From these four equations, every projectile question follows. Time of flight for a level launch and landing: set y=0 and discard t=0. Maximum height: set vy=0 to find the time, then substitute back. Range: substitute the time of flight into the horizontal equation. Speed at time t: combine vx=ucosθ and vy=usinθ−gt using Pythagoras.
A short worked example. A stone is thrown from ground level at 20 m/s at 30∘ above the horizontal. Find the range over level ground.
ux=20cos30∘=103 m/s, uy=20sin30∘=10 m/s. Time of flight: 0=10t−21(9.8)t2, so t=20/9.8≈2.04 s. Range: x=103×2.04≈35.3 m to 3 s.f.
A common pitfall is using the resultant initial speed in vertical suvat equations. The vertical motion only sees usinθ, not u. Another is forgetting that on uneven ground (launch height different from landing height), the vertical equation has a non-zero target y, and the resulting quadratic in t usually has two solutions of which only the positive one is physical. A third is mixing degrees and radians — make sure your calculator is in degrees mode.
For worked range, height, and uneven-ground problems, see the Projectile Motion lesson.
Friction
Friction is the contact force that opposes relative motion between two surfaces. On 9MA0 the simplified model gives the maximum frictional force as Fmax=μR, where μ is the coefficient of friction and R is the normal reaction.
Static friction takes whatever value is required (up to μR) to keep the body in equilibrium. Limiting friction is the value μR itself, the maximum it can reach. Once the body moves, kinetic friction acts at F=μR in the direction opposite the motion.
The most common question is a body on a rough inclined plane. Resolve perpendicular to find R=mgcosθ. Along the slope, F=ma gives mgsinθ−μmgcosθ=ma for a body sliding down. The mass cancels: a=g(sinθ−μcosθ), which is positive when tanθ>μ.
A short worked example. A block of mass 4 kg rests on a rough horizontal table with μ=0.3. A horizontal force of 15 N is applied. R=mg=39.2 N, so maximum friction is μR=11.76 N. The applied force exceeds this, so the block moves. Net force =3.24 N, giving a=0.81 m/s2.
A common pitfall is using R=mg on a slope (it is mgcosθ). Another is treating friction as always equal to μR — that is the maximum; in equilibrium below the limit, friction equals the applied force, not μR. A third is sign errors — friction always opposes motion or attempted motion.
For inclined-plane and table problems with full friction analysis, see the Friction lesson.
Statics and Equilibrium
A body is in equilibrium when the resultant force is zero and the resultant moment is zero. On 9MA0 the problems are typically a particle held by several forces, or a rigid rod or beam in equilibrium under several forces and a pivot.
For a particle, ∑Fx=0 and ∑Fy=0. The standard example is a particle on two strings at different angles to the vertical: resolving horizontally and vertically gives two equations in the two tensions. A useful alternative for three forces is the triangle of forces — the three force vectors form a closed triangle when drawn head-to-tail.
For a rigid body you also need ∑M=0. The standard example is a ladder against a wall: weight at the centre, friction and normal reaction at the foot, normal reaction at the wall (usually modelled as smooth). Take moments about the foot to eliminate two unknowns. The "limiting equilibrium" version asks for the angle at which the ladder is on the point of slipping — friction at the foot is at its maximum μR.
A short worked example. A uniform ladder of mass 20 kg, length 5 m, leans against a smooth vertical wall, foot on rough ground, at 60∘ to the ground. Vertical equilibrium: Rg=196 N. Horizontal: F=Rw. Moments about the foot: Rw×5sin60∘=mg×2.5cos60∘, giving Rw=196/(23)≈56.6 N. So minimum μ=F/Rg≈0.289.
A common pitfall is forgetting to take moments at all, when force balance alone gives too few equations. Another is taking moments about a point where every force passes through, producing a trivially-true equation. Pick the pivot to eliminate the most unknowns.
For ladder problems, beams on supports, and limiting-equilibrium analysis, see the Statics and Equilibrium lesson.
Applications and Modelling
The final strand of the specification is modelling. Every mechanics question is built on idealisations — particles instead of extended bodies, light strings, smooth pulleys, no air resistance. Edexcel will sometimes ask you to identify these assumptions, justify them, or comment on their effect on the answer.
The standard modelling vocabulary is worth memorising precisely. Particle: size ignored, all forces act at one point. Light: mass negligible. Inextensible: does not stretch, so connected particles share the same speed and acceleration. Smooth: frictionless. Rough: friction present, coefficient μ given. Uniform: weight acts through the centre. Rigid: does not bend.
Typical questions read: "How would your answer change if the string were not light?" — a heavy string would mean the tension varies along its length, breaking the shared-T assumption and invalidating the connected-particle equations. Or: "Effect of ignoring air resistance?" — in reality, air resistance reduces both range and maximum height, so the modelled answer is an upper bound.
A common pitfall is vague modelling answers. "It would be different" scores nothing; "the tension would no longer be the same on both sides of the pulley, so the connected-particle equations would no longer share a common T" scores. Be specific.
For practice on modelling-comment questions and a vocabulary checklist, see the Applications and Modelling lesson.
Common Mark-Loss Patterns Across Mechanics
Across the whole mechanics section, a small set of habits accounts for a disproportionate share of lost marks. None of these are about content you do not know. They are all about content you do know, applied carelessly under time pressure.
- Skipping the force diagram. A clean labelled diagram is worth its weight in method marks. Mechanics questions where students go straight to algebra usually lose the easy initial marks.
- Using m instead of mg for weight. Mass and weight are different quantities. The force on a body due to gravity is mg, not m.
- Using R=mg on an inclined plane. On a slope of angle θ, the normal reaction is R=mgcosθ, not mg.
- Using suvat with non-constant acceleration. The five suvat equations are only valid when a is constant. For variable acceleration, switch to calculus immediately.
- Mixing sign conventions within a single question, especially in vertical motion under gravity. Pick a positive direction at the start and stick to it everywhere.
- Treating friction as always equal to μR. The formula F=μR gives the maximum static friction. In equilibrium, friction equals whatever is needed to balance the applied forces, up to the maximum.
- Confusing distance with displacement in variable-acceleration problems where the particle changes direction. Read the question carefully.
- Failing to resolve along the slope in inclined-plane problems. Resolving horizontally and vertically also works but produces messier algebra.
- Forgetting to take moments in static-equilibrium problems involving extended bodies. Force balance alone is not enough.
- Vague modelling comments. "The assumption affects the answer" scores zero; "the assumption that the string is light means the tension is the same throughout — if the string had mass, the tension would vary along its length" scores.
- Not showing enough working. Edexcel mark schemes award method marks generously when the working is clear and the equations are quoted before substitution. A correct final answer with no working can score fewer marks than an incorrect final answer with clean method.
A revision plan that explicitly drills these habits — not just the content — will move your grade more than another pass through the textbook.
Recommended Six-Week Revision Plan
This plan is designed for a candidate who has covered the mechanics content in lessons but wants to revise it cleanly before the exam. It assumes about 5-6 hours per week on this section. Adjust pace if you are starting earlier or later.
| Week | Topics | Practice |
|---|---|---|
| 1 | Constant-acceleration kinematics; vertical motion under gravity | 30 suvat problems including 10 vertical-motion under gravity; 10 velocity-time graph problems |
| 2 | Variable acceleration via calculus; vectors in mechanics | 15 differentiate/integrate motion problems; 10 distance-vs-displacement problems; 10 vector-suvat problems |
| 3 | Forces and Newton's laws; connected particles and pulleys | 15 F=ma problems on horizontal, vertical and inclined surfaces; 10 connected-particle / pulley problems |
| 4 | Friction; statics and equilibrium; moments | 10 friction problems; 10 ladder/beam-on-supports problems; 10 moments problems |
| 5 | Projectile motion; modelling and assumptions | 15 projectile problems including 5 on uneven ground; 10 modelling-comment questions |
| 6 | Mixed practice; targeted review of weakest topics; full Paper 3B question sets | One full mixed problem set per day; review marking-scheme working for any question scoring below 60% |
The point of the plan is to keep moving forward while maintaining contact with earlier topics. Do not spend three weeks on suvat and run out of time before projectiles. By the end of week 5, every topic in the section should have had focused contact and a practice round. Week 6 is consolidation and weakness-targeting.
A useful discipline through the whole plan is to treat any question you got wrong not as a mistake but as a diagnostic. Was it a content gap? A method error? A force missed off the diagram? A sign-convention slip? Logging the cause means your next review session targets the right thing.
How LearningBro's Edexcel A-Level Maths Mechanics Course Helps
LearningBro's Edexcel A-Level Maths: Mechanics course is built around the structure of this guide. Each of the ten lessons covers one section of the 9MA0 specification, in the order Edexcel teaches it, with worked examples, practice questions and full mark-scheme-style solutions. Lessons end with a short review and quick-recall questions designed for spaced revisits.
The course is designed to be used in two ways. As a first pass, you can work through the lessons in order, building each topic on the last — kinematics before forces, forces before connected particles, all of it before projectiles. As a revision tool, you can drop into any lesson and work the practice independently — for example, drilling moments for a week before mocks. The AI tutor is available throughout to give targeted hints when you get stuck, without giving away full solutions, and to mark your written working with structured feedback.
If you want one place to revise this section of the spec well, with realistic practice and clean explanations of every topic, the full course is the right next step. Start with the Edexcel A-Level Maths: Mechanics course.