Overview
This lecture provides a rapid summary of all key content for Edexcel GCSE Physics Paper 1, spanning topics 1 to 7 and suitable for both combined and separate science students.
Key Concepts in Measurement and Units
- Physical quantities have units (e.g., meters, seconds), and prefixes denote size (e.g., kilo = ×1,000, micro = ÷1,000,000).
- Convert units by multiplying or dividing by the conversion factor depending on whether you want a bigger or smaller number.
- Standard form expresses large or small numbers as powers of ten (e.g., 5 × 10^-6 m).
Forces and Motion
- Forces can be contact (e.g., friction, tension) or non-contact (e.g., gravity, magnetism).
- Forces are vectors: described by magnitude and direction, represented by arrows.
- Resultant force is found by adding vectors (opposing directions need negatives).
- Balanced forces mean constant velocity (Newton's First Law); unbalanced forces cause acceleration (Newton's Second Law: F = ma).
- Scalars have only magnitude (e.g., speed); vectors also have direction (e.g., velocity, displacement).
- Weight = mass × gravitational field strength (g, usually 9.8 or 10 N/kg).
- Work done = force × distance (energy transferred).
Kinematics and Graphs
- Speed/velocity = distance/time; acceleration = change in velocity/time.
- Distance-time graph gradient = speed; velocity-time graph gradient = acceleration; area under velocity-time graph = distance.
- Acceleration due to gravity on Earth = 9.8 m/s².
- Equations of motion (SUVAT) predict displacement, velocity, acceleration, or time.
Newton’s Laws and Momentum
- First Law: constant motion with no resultant force; inertia resists motion change.
- Second Law: F = ma; acceleration proportional to resultant force.
- Third Law: every action has equal and opposite reaction.
- Stopping distance = thinking distance + braking distance; braking distance increases with speed².
- Momentum = mass × velocity; total momentum is conserved in collisions.
Energy Stores and Transfers
- Energy cannot be created/destroyed; stored as kinetic, gravitational potential, elastic potential, thermal, chemical, etc.
- Kinetic energy = ½mv²; GPE = mgh; elastic potential = ½ke²; thermal = mcΔT (specific heat capacity).
- Closed systems conserve total energy; energy can be lost to surroundings as heat due to friction/air resistance.
Waves and the EM Spectrum
- Longitudinal waves: oscillations parallel to energy transfer (e.g., sound); transverse waves: perpendicular (e.g., light).
- Wavelength (λ): distance between peaks; frequency (f): waves per second; wave speed = fλ.
- Reflection: angle in = angle out; refraction: change in speed and direction at boundaries.
- EM spectrum: radio, micro, infrared, visible, UV, X-ray, gamma; higher frequency = more energy.
Sound, Ultrasound, and Imaging
- Human hearing range: 20 Hz to 20 kHz; above this is ultrasound.
- Ultrasound used for medical imaging and sonar; some waves reflect, some transmit at boundaries.
- Seismic P-waves travel through liquids; S-waves cannot (evidence for Earth's liquid core).
Lenses, Color, and Reflection
- Convex lenses converge light to a focus; concave lenses diverge rays.
- Magnification = image height/object height.
- Color depends on reflected/emitted wavelengths; objects absorb some wavelengths and reflect others.
Radioactivity and Nuclear Physics
- Radioactive decay emits alpha (α), beta (β), or gamma (γ) radiation.
- Alpha: 2 protons + 2 neutrons, stopped by paper; Beta: electron, stopped by aluminum; Gamma: EM wave, reduced by lead/concrete.
- Activity (Bq) = decays per second; half-life = time for activity/mass to halve.
- Nuclear fission splits heavy nuclei, releasing energy and neutrons (chain reactions).
- Fusion combines light nuclei (e.g., in stars); both fission and fusion release energy due to mass–energy conversion.
Astronomy
- Solar system: sun, eight planets, asteroid belt, moons (natural satellites).
- Stars form from nebulae; life cycle includes main sequence, giant/supergiant, supernova, white/black dwarf, neutron star, black hole.
- Satellites: geostationary (communications), elliptical (reconnaissance); centripetal force acts towards orbit center.
- Red-shift of galaxies supports the Big Bang theory; cosmic microwave background is further evidence for universal expansion.
Key Terms & Definitions
- Vector — quantity with magnitude and direction.
- Scalar — quantity with only magnitude.
- Resultant Force — single force replacing combined effect of all forces acting on an object.
- Momentum — mass × velocity, conserved in collisions.
- Work Done — energy transferred by force over distance.
- Half-life — time for activity or mass of a radioactive sample to halve.
- Specific Heat Capacity (SHC) — energy needed to raise 1 kg of substance by 1°C.
- Refraction — bending of a wave as it passes from one medium to another.
- Red-shift — stretching of light waves due to objects moving away.
Action Items / Next Steps
- Review relevant equations and practice calculation problems, especially SUVAT, energy, and wave equations.
- Complete any assigned questions or past papers on these topics.
- Prepare revision cards for definitions, laws, and formulas for quick recall before the exam.