Numbers
Edexcel GCSE Combined Science Physics 1SC0
Key Concepts of Physics
Motion and Forces
Topic overviewScalar and vector quantitiesExamples of vectors and scalars, and velocitySpeed, distance, time and distance-time graphsAcceleration and the equation v squared minus u squaredVelocity-time graphs and free fallMeasuring speed in the laboratory, and typical everyday speedsNewton's first law, and investigating force, mass and accelerationNewton's second and third lawsWeight, mass and gravitational field strengthReaction time, stopping distance and large decelerationsFactors affecting stopping distance and reaction time
Conservation of Energy
Waves
Light and the Electromagnetic Spectrum
Topic overviewProperties of electromagnetic wavesInvestigating refraction in glass blocksThe groups of the electromagnetic spectrumThe continuous spectrum, and what our eyes can detectHow radiation is generated, and why danger rises with frequencyHarmful effects of excessive exposure to radiationUses of electromagnetic radiation
Radioactivity
Topic overviewThe atom and the size of atomsIsotopes, atomic number and mass numberRelative masses and charges of subatomic particlesElectron orbits and energy levelsForming ions, and how the atomic model changedTypes of ionising radiationBackground radiation and detecting radioactivityAlpha, beta and gamma, and their penetrating powerBeta-minus and beta-plus decayEffects of decay on atomic number and mass numberBalancing nuclear equationsActivity and the becquerelHalf-life and the randomness of decayHalf-life calculationsThe dangers of ionising radiationSafety precautions, contamination and irradiation
Energy – Forces Doing Work
Topic overviewEnergy stores and energy transfer diagramsChanging a system's energy, and measuring work doneWork done and the energy changes it causesGravitational potential and kinetic energy calculationsDissipation and wasted energyPower as the rate of energy transferThe watt, and calculating efficiency
Forces and Their Effects
Electricity and Circuits
Topic overviewThe atom, and drawing circuit diagramsSeries and parallel circuitsPotential difference and the voltmeterEnergy transferred by moving chargeCurrent, charge and measuring currentResistance and the equation V = IRResistors in series and in parallelDesigning circuits to test componentsInvestigating resistance in circuitsCurrent-potential difference graphs for componentsLight-dependent resistors and thermistorsThe heating effect of an electric currentUses of the heating effect, and the equation E = IVtPower as energy transferred per secondCalculating electrical powerEnergy transfer in domestic devices, and power ratingsDirect and alternating currentAlternating current and the UK mains supplyLive and neutral wires, earthing and fusesFuses in the live wire, mains voltages and electrical dangers
Magnetism and the Motor Effect
Electromagnetic Induction
Particle Model
Topic overviewKinetic theory and differences in densityCalculating density, and investigating itChanges of state and internal energySpecific heat capacitySpecific latent heat and thermal insulationInvestigating the specific heat capacity of waterGas pressure and the motion of particlesAbsolute zero and the kelvin scale
Radioactivity
Half-life and the randomness of decay
- 3 things to know
- Paper 5
Overview
Half-life defined by undecayed nuclei and by activity, the fraction left after one or two half-lives, and why random decay still gives reliable predictions for a large sample.
What you need to know
Answer each one before you reveal it.
Your recallNot started
Key term
What fraction of the original undecayed nuclei is left after two half-lives?
Key term
Why can half-life still be used to make reliable predictions about a radioactive sample?
Questions from this subtopic
Each one with the model answer underneath.
- 1
What is meant by the half-life of a radioactive isotope?
Model answer
It is the time taken for half the undecayed nuclei in a sample to decay.
- 2
State what the half-life of a radioactive isotope means in terms of activity.
Model answer
It is the time taken for the activity of a source to fall to half its value.
- 3
A sample contains 8.0 × 10⁸ undecayed nuclei. How many are left undecayed after one half-life?
Model answer
4.0 × 10⁸ undecayed nuclei remain.
- 4
Does the half-life of an isotope depend on how large a sample you start with?
Model answer
No, the half-life is the same whatever the size of the sample.
- 5
What fraction of the original undecayed nuclei is left after two half-lives?
Model answer
One quarter of the original nuclei are left undecayed.
- 6
Can it be predicted when one particular nucleus in a sample will decay?
Model answer
No, the decay of any individual nucleus is completely random.
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