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LearnAQA7357First teaching 2017Paper 2 · Pure and MechanicsForces and Newton's laws

Paper 2 · Module

Forces and Newton's laws

8 subtopics≈ 280 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
Newton’s laws and F = ma
Resultant force equals mass times acceleration. It links the forces on an object to how its motion changes, and with suvat it lets you predict exactly where the object will be.
≈ 35 min
Connected particles and pulleys
Two objects joined by a taut string move together with the same acceleration. Write $F=ma$ for each one (or for the whole system) and solve for the acceleration and the tension.
≈ 40 min
Lifts and vertical motion
Why you feel heavy as a lift sets off upwards and light as it slows: the floor pushes with $R=m(g+a)$ . The same $F=ma$ handles cables, parachutes and anything else moving up or down.
≈ 30 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
Motion on inclined planes
Gravity pulls along the slope with $mg\sin\alpha$ ; friction, if any, opposes the motion with $\mu mg\cos\alpha$ . Put them into $F=ma$ along the slope, then let suvat finish the job.
≈ 35 min