Overview
This lecture provides a concise summary of all key topics for AQA GCSE Physics Paper 2, covering Forces, Waves, Magnetism, and (for triple) Space, with core definitions, formulas, and exam tips.
Forces & Motion
- A force is any push or pull; it can be contact (touching) or non-contact (magnetism, gravity).
- Forces are represented as vectors, showing both direction and magnitude (size).
- Resultant force is the sum of all forces acting on an object; opposite directions are negative.
- If forces are balanced, object moves at constant velocity (Newton's 1st Law).
- Scalars have magnitude only; vectors have magnitude and direction.
- Weight = mass × gravitational field strength; on Earth, g = 9.8 or 10 N/kg.
- Work done = force × distance moved; for lifting, work = mass × g × height (gravitational potential energy).
- Hooke’s Law: force = spring constant × extension; valid for elastic deformation.
- Energy stored in a spring = ½ × spring constant × (extension)².
- A moment (turning force) = force × perpendicular distance to pivot.
- Pressure = force ÷ area; unit is pascal (Pa); pressure in liquids = depth × density × g.
- Speed = distance ÷ time; velocity is speed with direction.
- Acceleration = change in velocity ÷ time; area under velocity–time graph = distance.
- Newton’s 2nd Law: force = mass × acceleration.
- Newton’s 3rd Law: every action has an equal and opposite reaction.
- Stopping distance = thinking distance + braking distance; doubling speed quadruples braking distance.
- Momentum = mass × velocity; total momentum before and after a collision is conserved.
Waves
- Waves transfer energy without transferring matter.
- Longitudinal waves: oscillations parallel to direction of energy transfer (e.g. sound, P-waves).
- Transverse waves: oscillations perpendicular to energy transfer (e.g. light, water, S-waves).
- Amplitude: maximum displacement; wavelength: length of one complete wave.
- Frequency = number of waves per second; f = 1 ÷ period.
- Wave speed = frequency × wavelength (v = fλ).
- Reflection: angle of incidence = angle of reflection; refraction: wave changes direction at boundary.
- Electromagnetic (EM) waves travel in vacuum; spectrum includes radio, microwave, infrared, visible, UV, X-rays, gamma rays.
- Higher frequency EM waves have more energy.
- Ionising radiation (UV, X-ray, gamma) can cause mutations/cancer.
- Ultrasound and sonar use reflected sound waves for imaging.
- Lenses refract light to focus or spread rays; convex converge, concave diverge.
- Magnification = image height ÷ object height.
Magnetism & Electromagnetism
- Permanent magnets create constant magnetic fields; induced magnets only in a magnetic field.
- Magnetic field lines go north to south; field strength = magnetic flux density (B).
- Current in a wire creates magnetic field (right-hand rule).
- Motor effect: current-carrying wire in magnetic field experiences force (F = BIL).
- Electric motors use coils and commutators to produce rotation.
- Generator effect: moving a wire in a magnetic field induces current/potential.
- Transformers use coils and iron cores to change voltage; must use AC to induce current in secondary coil.
- Ratio of coils = ratio of voltages (Np/Ns = Vp/Vs); step-up increases voltage, step-down decreases.
Space Physics (Triple Only)
- Solar system: sun, 8 planets, asteroid belt, dwarf planets, moons (natural satellites).
- Stars form from nebulae; main sequence = stable fusion; red giants expand, white/black dwarfs cool or supernova leaves neutron star/black hole.
- Orbits: satellites move at constant speed but velocity changes (centripetal force).
- Red-shift of galaxies indicates universe expansion (evidence for Big Bang).
- Cosmic microwave background radiation is further evidence for Big Bang.
Key Terms & Definitions
- Force — a push or pull on an object.
- Scalar — quantity with only magnitude.
- Vector — quantity with magnitude and direction.
- Resultant Force — the sum of all forces acting on an object.
- Moment — turning effect of a force.
- Momentum — mass × velocity.
- Amplitude — maximum displacement in a wave.
- Wavelength (λ) — distance between two peaks/troughs in a wave.
- Frequency (f) — waves per second (Hz).
- Magnetic Flux Density (B) — strength of a magnetic field.
- Centripetal Force — force causing circular motion.
Action Items / Next Steps
- Review formula sheet, especially Newton’s equations and wave formulas.
- Practice drawing and interpreting graphs (force diagrams, speed–time, distance–time).
- Triple students: study space physics and associated lifecycle diagrams.
- Complete any assigned practice questions on forces, waves, and magnetism.