Thermodynamics, Radiation, Oscillations and Cosmology

Worked examples (9)

• 1Energy to heat water using ΔE = mcΔθ (2 marks)
• 2Energy to melt ice using ΔE = LΔm (2 marks)
• 3Temperature rise from an immersion heater (2 marks)
• 4Specific heat capacity by electrical heating (4 marks)
• 5Specific latent heat of vaporisation from power and rate of boiling (4 marks)
• 6Method of mixtures — final temperature (4 marks)
• 7Melting ice then warming the water (5 marks)
• 8Correcting for heat loss to find the true SHC (6 marks)
• 9Specific latent heat from mass boiled off, allowing for heat loss (6 marks)

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• ✓Model answer — Adapted from Edexcel IAL Physics Unit 5 (CP13)
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• ✓Model answer — Adapted from Edexcel IAL Physics Unit 5

Worked examples (9)

• 1Mass defect of a helium nucleus (2 marks)
• 2Converting 1 u to MeV/c² (2 marks)
• 3Balancing a uranium-235 fission equation (3 marks)
• 4Binding energy per nucleon of helium-4 (4 marks)
• 5Energy released in deuterium–tritium fusion (5 marks)
• 6Energy released per fission in joules (5 marks)
• 7Why both fission and fusion release energy (6 marks)
• 8Why fusion needs extremely high temperatures (6 marks)
• 9Comparing nuclear and chemical energy per unit mass (6 marks)

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Worked examples (9)

• 1Converting a temperature to kelvin (2 marks)
• 2Pressure of a gas from pV = NkT (2 marks)
• 3Boyle's law at constant temperature (2 marks)
• 4Pressure from a number of moles (4 marks)
• 5Mean kinetic energy of a molecule (3 marks)
• 6Root-mean-square speed of a molecule (4 marks)
• 7Finding the temperature to double the r.m.s. speed (5 marks)
• 8Combined gas behaviour with changing p, V and T (6 marks)
• 9Core Practical 14 — verifying Boyle's law from a graph (6 marks)

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Worked examples (6)

• 1Identifying radiation from penetration (2 marks)
• 2Balancing an alpha decay equation (2 marks)
• 3Half-life from the decay constant (3 marks)
• 4Carbon dating — finding the age (4 marks)
• 5CP15 — absorption coefficient of lead (6 marks)
• 6Count rate remaining after several half-lives (5 marks)

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• ✓Model answer — Adapted from Edexcel IAL Physics Unit 5 (CP15)
• ✓Model answer — Adapted from Edexcel IAL Physics Unit 5
• ✓Model answer — Adapted from Edexcel IAL Physics Unit 5 (synoptic with Unit 4)

Worked examples (9)

• 1Redshift of a receding galaxy (2 marks)
• 2Recessional velocity from a shifted spectral line (3 marks)
• 3Recessional velocity from Hubble's law (2 marks)
• 4Hubble constant as the gradient of a $v$–$d$ graph (4 marks)
• 5Age of the universe from $H_0$ (4 marks)
• 6Blueshift of an approaching galaxy (4 marks)
• 7Age of the universe in years and the constant-rate assumption (5 marks)
• 8Peak wavelength of the CMB (5 marks)
• 9Fate of the universe and critical density (6 marks)

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Worked examples (9)

• 1Angular frequency and maximum values (2 marks)
• 2Acceleration from displacement (2 marks)
• 3Frequency and period from angular frequency (3 marks)
• 4Speed at a given displacement (4 marks)
• 5Period of a mass–spring system (4 marks)
• 6Length of a simple pendulum (4 marks)
• 7Maximum kinetic energy in SHM (5 marks)
• 8Verifying SHM from acceleration–displacement data (5 marks)
• 9Core Practical 16 — spring constant from a T² vs m graph (6 marks)

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Worked examples (9)

• 1Field strength from the weight of a mass (2 marks)
• 2Gravitational force between two masses (3 marks)
• 3One similarity and one difference of the two fields (2 marks)
• 4Field strength and potential near a planet (4 marks)
• 5Orbital speed of a satellite (4 marks)
• 6Change in gravitational potential energy in orbit (4 marks)
• 7Derive Kepler's third law $T^2\\propto r^3$ (5 marks)
• 8Radius of a geostationary orbit (6 marks)
• 9Escape velocity from a planet (5 marks)

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Worked examples (6)

• 1Luminosity from the Stefan–Boltzmann law (2 marks)
• 2Luminosity of a star from its radius (4 marks)
• 3Effect of doubling the temperature on power (4 marks)
• 4Peak wavelength and surface flux together (4 marks)
• 5Comparing two stars' luminosities (5 marks)
• 6Radius of a cool, luminous red giant (6 marks)

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Worked examples (9)

• 1Radiant flux intensity at a distance (2 marks)
• 2Peak wavelength, temperature and spectral class (2 marks)
• 3Placing a star on the HR diagram (2 marks)
• 4Distance to a star from luminosity and intensity (4 marks)
• 5Luminosity of a star from its measured intensity (4 marks)
• 6Comparing intensities of two identical stars (3 marks)
• 7Distance to a galaxy from a Type Ia supernova (5 marks)
• 8Why a red giant is so much more luminous (5 marks)
• 9Evolution of a Sun-like star on the HR diagram (6 marks)

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