Key term
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 strengthCircular motion and centripetal forceInertial mass and momentumCollisions, and force as the rate of change of momentumReaction 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 detectAbsorption, transmission and the velocity of electromagnetic wavesHow 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
Topic overviewMagnetic poles, permanent and induced magnetsUses of magnetic materialsThe magnetic field around a bar magnetPlotting compasses and the Earth's magnetic fieldThe magnetic effect of an electric currentSolenoids and electromagnetsThe motor effect and Fleming's left-hand ruleThe force on a conductor in a magnetic field
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 calculations
- 2 things to know
- Paper 5
Overview
Activity or nuclei remaining after a number of half-lives, finding a half-life from a fall in activity or from a graph, and the percentage left after three half-lives.
What you need to know
Answer each one before you reveal it.
Your recallNot started
Key term
The activity of a source falls from 1600 Bq to 100 Bq in 20 days. What is the half-life of the isotope?
Questions from this subtopic
Each one with the model answer underneath.
- 1
A source has an activity of 800 Bq and a half-life of 6 hours. What is its activity after 24 hours?
Model answer
The activity is 50 Bq, because four half-lives have passed.
- 2
The activity of a source falls from 1600 Bq to 100 Bq in 20 days. What is the half-life of the isotope?
Model answer
The half-life is 5 days, because the activity halved four times.
- 3
A sample holds 6.4 × 10⁷ undecayed nuclei of an isotope whose half-life is 3 years. How many are left undecayed after 9 years?
Model answer
8.0 × 10⁶ nuclei remain, after three half-lives.
- 4
What percentage of a radioactive sample is left undecayed after three half-lives?
Model answer
12.5% of the sample is left undecayed.
- 5
An isotope has a half-life of 15 hours. How long does its activity take to fall to one eighth of its starting value?
Model answer
It takes 45 hours, which is three half-lives.
- 6
A graph shows the activity of a source falling from 400 Bq at the start to 200 Bq after 7 hours. What is the half-life?
Model answer
The half-life is 7 hours.
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