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
Deformation of Solids
Strain energy and force–extension graphs
- 3 things to know
- Unit A2 1
Overview
Recall questions on what strain energy is, the two forms of the equation and why there is a factor of ½, the area under a force–extension graph, the effect of doubling the extension, finding the energy under a curved graph, what the area of a loading and unloading loop represents, and a catapult calculation.
What you need to know
Answer each one before you reveal it.
Your recallNot started
Key term
What is meant by strain energy?
Key term
Why does the equation for strain energy carry a factor of ½?
Questions from this subtopic
Each one with the model answer underneath.
- 1
What is meant by strain energy?
Model answer
Strain energy is the elastic potential energy stored in a material because work has been done in stretching or compressing it.
- 2
State the equation for strain energy in both of its forms and define every symbol.
Model answer
E = ½Fx = ½kx², where E is the strain energy in joules, F the final force in newtons, x the extension in metres and k the spring constant in N m⁻¹.
- 3
Why does the equation for strain energy carry a factor of ½?
Model answer
The force grows steadily from zero to F as the material stretches, so the average force doing the work is F/2 rather than F.
- 4
What does the area under a force–extension graph represent?
Model answer
The area under the graph is the work done on the material, which is the strain energy stored in it, in joules.
- 5
Calculate the strain energy stored in a spring of spring constant 200 N m⁻¹ extended by 4.0 cm.
Model answer
E = ½kx² = ½ × 200 × (0.040)² = 0.16 J.
- 6
A force of 8.0 N produces an extension of 4.0 cm in a spring. Calculate the work done in stretching it.
Model answer
E = ½Fx = ½ × 8.0 × 0.040 = 0.16 J.
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