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LearnCambridge97092026–2027Paper 4 · MechanicsForces and equilibrium

Paper 4 · Module

Forces and equilibrium

4 subtopics≈ 140 min in total

Start the module: Forces, components and resultants Open graphing calculator

Forces, components and resultants
Every force has a size and a direction. Split each force into a horizontal and a vertical part, add the parts, and Pythagoras gives you the overall effect.
≈ 30 min
Equilibrium of a particle
A particle in equilibrium has zero resultant force. Resolve in two directions, set each total to zero, and you have two equations for two unknowns.
≈ 35 min
Friction
Friction is lazy: it only pushes back as hard as it needs to, up to a maximum of $\mu R$ . Reach that maximum and the object is on the point of moving.
≈ 35 min
Inclined planes
Tilt the axes to match the slope. Weight splits into $mg\sin\alpha$ down the slope and $mg\cos\alpha$ into it, and friction points whichever way stops the slide.
≈ 40 min