Key term
OCR A-Level Physics A H556
Practical Skills in the Written Papers
The Practical Endorsement
Topic overviewAnalogue and digital measuring instrumentsImproving accuracy with repeat timing, fiducial markers and plumb linesTiming, calipers and micrometersConstructing and testing circuitsSignal generators and oscilloscopesGenerating and measuring wavesData loggers, modelling software and ionising radiation
Physical Quantities and Units
Making Measurements and Analysing Data
Nature of Quantities
Motion
Forces in Action
Work, Energy and Power
Materials
Newton’s Laws of Motion and Momentum
Charge and Current
Energy, Power and Resistance
Electrical Circuits
Waves
Topic overviewProgressive waves and their propertiesThe wave equationReflection, refraction and diffractionWave graphs and intensityThe electromagnetic spectrumPolarisationRefraction and refractive indexCritical angle and total internal reflectionThe principle of superpositionInterference, coherence and path differenceTwo-source interference, Young's double-slit experiment and the diffraction gratingForming stationary wavesStationary waves on strings and in air columnsMeasuring the speed of soundNode spacing, amplitude and phase in stationary wavesHarmonics and the fundamental mode
Quantum Physics
Thermal Physics
Topic overviewThermal equilibrium and absolute temperatureThe kinetic model of solids, liquids and gasesBrownian motion and internal energySpecific heat capacityMeasuring specific heat capacitySpecific latent heatMeasuring specific latent heatMoles, the Avogadro constant and kinetic theoryGas laws, the ideal gas equation and r.m.s. speedMaxwell-Boltzmann distribution, Boltzmann constant and internal energy
Oscillations
Gravitational Fields
Astrophysics and Cosmology
Topic overviewThe solar system and the birth of a starThe death of a low-mass starSupernovae, neutron stars and black holesThe Hertzsprung-Russell diagramEnergy levels and emission spectraAbsorption spectra and spectral linesPhoton energy and the diffraction gratingWien's law and Stefan's lawAstronomical distances, parallax and the cosmological principleDoppler shift and Hubble's lawThe expanding universe and the Big BangEvidence for the Big Bang and dark energy
Capacitors
Topic overviewCapacitance and charging a capacitorCapacitors in seriesCapacitors in parallel and combined circuitsEnergy stored by a capacitorCharging and discharging through a resistorInvestigating capacitor dischargeThe time constantIterative modelling, exponential decay and the constant-ratio property
Electric Fields
Electromagnetism
Nuclear and Particle Physics
Topic overviewAlpha-particle scattering and the nuclear modelProton number, nucleon number and isotopesThe strong nuclear force and nuclear radiusParticles, antiparticles and hadronsLeptons and the quark modelQuark composition and chargesBeta decay in the quark modelRadioactive decay and the three radiationsNuclear decay equationsActivity, decay constant and half-lifeExponential decay and radioactive datingMass-energy equivalenceAnnihilation, mass defect and binding energyBinding energy per nucleon and induced fissionThe fission reactor and nuclear wasteNuclear fusion and balancing nuclear equations
Gravitational Fields
Newton's law of gravitation
- 3 things to know
- Papers 1, 2 and 3
Overview
Recall questions on the statement of the law, the inverse square relationship, and the gravitational constant.
What you need to know
Answer each one before you reveal it.
Your recallNot started
Key term
In the equation F = −GMm/r², what does the symbol r represent?
Key term
If the distance between two point masses is doubled, what happens to the gravitational force between them?
Questions from this subtopic
Each one with the model answer underneath.
- 1
State Newton's law of gravitation.
Model answer
The gravitational force between two point masses is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.
- 2
If the distance between two point masses is doubled, what happens to the gravitational force between them?
Model answer
The gravitational force decreases to one quarter of its original value, because force is inversely proportional to the square of the separation.
- 3
Write the equation for the gravitational force between two point masses and define each symbol.
Model answer
F = −GMm/r², where G is the gravitational constant, M and m are the two masses, and r is the separation between their centres.
- 4
In the equation F = −GMm/r², what does the symbol r represent?
Model answer
The distance between the centres of the two point masses.
- 5
What does the negative sign in the gravitational force equation F = −GMm/r² indicate?
Model answer
It indicates that the force is attractive, acting in the opposite direction to increasing separation (i.e., directed towards the other mass).
- 6
Why is the gravitational force assigned a negative value in the equation F = −GMm/r²?
Model answer
Because gravitational force is always attractive, pulling masses together rather than pushing them apart, so it acts opposite to the direction of increasing r.
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