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
- 7 subtopics
- 21 things to know
- Papers 1, 2 and 3
What Gravitational Fields covers
Newton's law of gravitation and the field it describes: field strength, Kepler's laws and orbits, and gravitational potential and potential energy.
Where it is assessed
Papers 1, 2 and 3
Newtonian world, astrophysics and particles, drawn on across the papers.
Check the OCR specification ↗The 7 subtopics
Each one has its own page.
- Gravitational fields and field strengthRecall questions on modelling a sphere as a point mass, field lines, and g as force per unit mass.Open →
- Newton's law of gravitationRecall questions on the statement of the law, the inverse square relationship, and the gravitational constant.Open →
- Field strength of a point mass and the uniform field near EarthRecall questions on gravitational field strength g = −GM/r² for a point mass with calculations, why the field is approximately uniform near the Earth's surface, and why g equals the acceleration of free fall.Open →
- Kepler's laws and orbital motionRecall questions on the three laws and on gravity supplying the centripetal force for an orbit.Open →
- Orbital period and geostationary orbitsRecall questions on T² ∝ r³, and on the conditions for and uses of a geostationary orbit.Open →
- Gravitational potentialRecall questions on gravitational potential and why it is negative, V = −GM/r, its unit and where it applies, and finding and calculating the change in potential between two points.Open →
- Gravitational potential energy and escape velocityRecall questions on gravitational potential energy E = −GMm/r and its link to potential, how it changes with distance, the area under a force-distance graph, and deriving and calculating escape velocity.Open →
What you need to know
Answer each one before you reveal it.
Your recallNot started
Key term
In the gravitational potential energy equation E = −GMm/r, what do M, m and r represent?
Key term
State the unit of gravitational field strength.
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What phenomenon do fields provide a model for, and what does this mean?
Key term
In the equation F = −GMm/r², what does the symbol r represent?
Numbers
When deriving the orbital period equation, what is the first step involving forces?
Numbers
Write the equation relating orbital period T to orbital radius r for a body orbiting a central mass M.
Numbers
After substituting v = 2πr/T into v² = GM/r, what final rearrangement gives the orbital period equation?
Key term
Define gravitational potential at a point.
Key term
In the derivation of escape velocity, what relationship exists between kinetic energy and gravitational potential energy?
Evaluation
State the equation for gravitational field strength at a distance from a point mass and define each term.
Key term
In the equation g = −GM/r², what physical quantity does M represent?
Key term
State Kepler's first law of planetary motion.
Key term
In the equation V = −GM/r, what does G represent?
Key term
In which direction do gravitational field lines point around a mass?
Key term
If the distance between two point masses is doubled, what happens to the gravitational force between them?
Numbers
Which formula is used to calculate the gravitational field strength at a given distance from a point mass?
Key term
What does Kepler's second law state about the motion of planets?
Key term
What substitution for orbital speed v is made when deriving the relationship between T and r?
Numbers
State the equation for gravitational potential at distance r from a point mass M.
Key term
On a force–distance graph for a point or spherical mass, what does the area under the curve represent?
Take Gravitational Fields further
The same content, four other ways.
Commonly confused
Pairs that lose marks when they are blurred together.
Gravitational field strength vs Gravitational potential
Gravitational field strength: force per unit mass. Gravitational potential: work per unit mass from infinity.
Uniform field vs Radial field
Uniform field: field with constant magnitude and direction. Radial field: field directed toward or away from a central source.
Escape velocity vs Orbital velocity
Escape velocity: minimum launch speed needed to escape a gravitational field. Orbital velocity: tangential speed required for a particular orbit.
Questions from this topic
Each one with the model answer underneath.
- 1
What property must an object possess in order to produce a gravitational field?
Model answer
Mass
- 2
When modelling the gravitational effects of a spherical object, where is its mass considered to be concentrated?
Model answer
At a single point located at the centre of the sphere
- 3
Under what condition is it valid to treat a spherical mass as a point mass at its centre?
Model answer
When calculating gravitational effects at positions outside the sphere
- 4
What are gravitational field lines used for?
Model answer
To map and represent gravitational fields
- 5
In which direction do gravitational field lines point around a mass?
Model answer
Towards the centre of the mass (in the direction a test mass would accelerate)
- 6
Explain why gravitational field lines around an isolated planet are drawn pointing inward rather than outward.
Model answer
Because a test mass placed in the field would experience a force directed towards the planet's centre, and field lines show the direction of this force
What is inside Levo
Six ways to work the same material.
Gravitational Fields revision questions
- What does Gravitational Fields cover in OCR A-Level Physics A?
- 7 subtopics: gravitational fields and field strength, newton's law of gravitation, field strength of a point mass and the uniform field near earth, kepler's laws and orbital motion, orbital period and geostationary orbits, gravitational potential and gravitational potential energy and escape velocity. Each one has its own page with questions and model answers.
- How is Gravitational Fields organised?
- By the OCR H556 specification, subtopic by subtopic, so it matches the order you are taught it in.
Every question in Gravitational Fields, on a schedule.
Attempt a question from memory, write the correct version, then attempt it again. Levo records the jump between your first attempt and your last, and brings each question back on the day you are due to forget it.
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