Key term
CCEA A-Level Physics 1210
Physical Quantities, Scalars and Vectors
Moments and Equilibrium
Linear Motion and Dynamics
Newton's Laws of Motion
Linear Momentum and Impulse
Work, Energy and Power
Current, Charge and Potential Difference
Resistance and Resistivity
Topic overviewResistance and Ohm's lawOhmic and non-ohmic behaviourResistors in series and in parallelInvestigating current, voltage and resistance in series and parallel circuitsElectrical power and energy in resistive circuitsResistivity and the equation R = ρl/AMeasuring the resistivity of a metalCurrent–voltage characteristics of a conductor, a lamp and a diodeResistance, temperature and superconductivity
Internal Resistance and Potential Dividers
Topic overviewInternal resistance and terminal potential differenceConsequences of internal resistance for external circuitsMeasuring electromotive force and internal resistanceThe potential divider and variable outputPotential dividers in lighting and heating control circuitsLoaded potential dividers and output voltage calculations
Waves
Refraction
Lenses
Superposition, Interference and Diffraction
Topic overviewSuperposition of wavesStanding waves, nodes and antinodesStanding waves on stretched stringsStanding waves in a pipe closed at one endMeasuring the speed of sound with a resonance tubeConditions for observable interferencePath difference and phase differenceYoung's double slitDiffraction at a single slitThe diffraction grating
Quantum Physics
Wave-Particle Duality
Astronomy
Practical Skills and Data Analysis
Topic overviewChoosing and using measuring instrumentsPrecision, accuracy and recording measurementsUsing the cathode ray oscilloscope to measure voltage and frequencyTables, graphs and presenting resultsLinearising a relationship and using the gradientAbsolute and percentage uncertaintyCombining uncertainties and uncertainty on a graphRandom and systematic error, reliability and refining an experiment
Deformation of Solids
Thermal Physics
Topic overviewBoyle's law, Charles's law and the pressure lawThe ideal gas equation pV = nRTThe Avogadro constant, the mole and pV = NkTInternal energy and the distribution of molecular energyThe kinetic theory equation pV = ⅓Nm⟨c²⟩Average molecular kinetic energy and temperatureAbsolute zero and the kelvin scaleSpecific heat capacity and the electrical method
Uniform Circular Motion
Simple Harmonic Motion
Topic overviewDefining simple harmonic motion and a = −ω²xDisplacement, velocity and acceleration: x = A cos ωtThe simple pendulum and T = 2π√(l/g)The loaded spiral spring and T = 2π√(m/k)SHM graphs and finding velocity from a gradientFree vibrations, forced vibrations and resonanceDamping: light, critical and over-damping
The Nucleus and Radioactive Decay
Topic overviewAlpha-particle scattering and the nuclear atomNuclear radius and nucleon numberThe density of nuclear matterAlpha, beta and gamma radiation: nature, penetration and rangeNuclear equations and changes in nucleon and proton numberThe random and exponential nature of radioactive decayActivity, the decay constant and A = −λNExponential decay calculations with A = A₀e^(−λt)Half-life and measuring it
Nuclear Energy, Fission and Fusion
Gravitational Fields
Electric Fields
Capacitors
Magnetic Fields
Charged Particles and Accelerators
Newton's Laws of Motion
Newton's third law
- 3 things to know
- Unit AS 1
Overview
Newton's third law of motion and why a rifle recoils when it is fired.
What you need to know
Answer each one before you reveal it.
Your recallNot started
Key term
State the conditions that a pair of forces must satisfy to form a Newton's third-law pair.
Key term
A book rests on a table. Identify the Newton's third-law partner of the upward contact force of the table on the book.
Questions from this subtopic
Each one with the model answer underneath.
- 1
State Newton's third law of motion.
Model answer
If body A exerts a force on body B, then body B exerts a force on body A that is equal in magnitude and opposite in direction.
- 2
State the conditions that a pair of forces must satisfy to form a Newton's third-law pair.
Model answer
The two forces must be equal in magnitude, opposite in direction, of the same type, and they must act on two different bodies.
- 3
Explain why the two forces in a Newton's third-law pair never cancel each other out.
Model answer
They act on two different bodies, so they never both appear in the resultant force on the same object and can never add to zero for either body.
- 4
A book rests on a table. Identify the Newton's third-law partner of the weight of the book.
Model answer
The partner is the gravitational pull of the book on the Earth, acting upwards on the Earth and equal in magnitude to the book's weight.
- 5
A book rests on a table. Identify the Newton's third-law partner of the upward contact force of the table on the book.
Model answer
The partner is the downward contact force of the book on the table, equal in magnitude and opposite in direction.
- 6
Explain why the upward contact force on a book resting on a table is not the third-law partner of the book's weight.
Model answer
The two act on the same body and are different types of force, one gravitational and one contact, and they are equal only because the book happens to be in equilibrium; they are a first-law balance, not a third-law pair.
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