Physics Unit 5

📚 Oct 2022

• A massive nucleus splits into two (or more) smaller nuclei/fragments (of roughly equal mass and some neutrons)

📚 Oct 2022

• Positrons annihilate with electrons to produce gamma radiation
• Gamma radiation can penetrate the body
• Half life is long enough to allow the procedure to be performed
• Half life is short enough to avoid unnecessarily large radiation dose

📚 Jun 2023

• The thickness of the track related to the ionising ability of the particle (not its mass)
• Alpha is strongly ionising and beta is only moderately ionising (so alpha tracks are thick and beta tracks are thin) [Allow a comparison of ionising power of alpha with that of beta]
• The shape of the track related to the mass of the particle (not its ionising ability)
• Alpha particles are massive particles and beta particles are not massive particles (so alpha tracks are straight and beta tracks are twisted) [Allow a comparison of alpha mass with beta mass]

📚 Jan 2024

• The binding energy per nucleon is the energy required to remove a nucleon from the nucleus
• Large energy is required to break the helium nucleus apart
• Decay products (of helium) have a lower binding energy per nucleon

📚 Jun 2022

• Momentum must be conserved (in the decay)
• The lead nucleus must recoil after the decay Or the lead nucleus moves in the opposite direction to the alpha particle

📚 Oct 2022

• Momentum is conserved (so the Ba nucleus recoils)
• Energy released is shared (randomly) between the β− and ν̅ Or the energy is shared between the 3 particles in the decay

📚 Oct 2023

• Momentum (and energy) is conserved
• (So) products must have \(E_{\text{k}}\) / momentum after the reaction (as the alpha particle has momentum before the reaction)

📚 Jan 2024

• A large nucleus splits (into two nuclei plus neutrons)
• The binding energy increases, (so energy is released) [Accept binding energy per nucleon increases] Or There is a decrease in (total) mass, (so energy is released)

📚 Jun 2023

• In the fusion process mass decreases
• So energy is released according to \(∆E = c^{2}∆m\) Or energy is released to conserve mass-energy Or binding energy per nucleon increases

📚 Jun 2024

• The alpha radiation will not penetrate the lead
• Or The lead will absorb the alpha radiation

📚 Jan 2024

• Alpha radiation would not pass through the sheet of paper
• No change in count rate when paper placed (between source and GM tube), so there can’t be any alpha radiation
• There can’t be any gamma radiation, as gamma radiation would pass through the aluminium sheet Or There can’t be any gamma radiation, as count rate decreases to background with aluminium sheet.
• It must be beta radiation as beta radiation would not pass through the aluminium sheet.

📚 Jun 2024

• EITHER
• Determine the background count (rate)
• Subtract background count (rate) from the recorded count (rate) to eliminate systematic error Or Subtract background count from the recorded count to prevent the count rate being overestimated
• OR
• Record the count for a longer time interval Or Record the count more than once and calculate a mean value
• This will reduce the effect of random variation on the count rate Or this will decrease the percentage uncertainty

📚 Jan 2023

• IC1 As the temperature increases the (average) kinetic energy of the (air) molecules increases
• IC2 So mean/average speed of the air molecules increases
• IC3 The (average/mean) change of momentum of air molecules when colliding with the tank/walls increases
• IC4 The rate of collision of air molecules with the tank/walls increases
• IC5 The rate of change of momentum increases and so the force on the tank/walls, increases
• IC6 The pressure (exerted by the gas) increases, since p = F/A

📚 Jun 2023

• IC1 The internal energy of the wax decreases during cooling Or The internal energy of the wax decreases as time passes
• IC2 The internal energy of the wax is the sum of potential energy and kinetic energy of the molecules
• IC3 As the temperature of the wax decreases, the (molecular) kinetic energy
• decreases
• IC4 Between times X and Y the (liquid wax is solidifying and the molecular) potential energy decreases
• IC5 Between times X and Y the temperature is constant and so there is no change in (molecular) kinetic energy
• IC6 At time Y the wax has solidified

📚 Jan 2024

• Energy is transferred from banana to liquid nitrogen
• The molecular potential energy of nitrogen molecules increases (as the nitrogen boils) Or This provides the latent heat of vaporisation (of the nitrogen) Or This provides the latent heat to change state (of the nitrogen)

📚 Jan 2023

• Energy is transferred (from the water) to the surroundings Or Not all of the energy from the heater is used to raise the water temperature

📚 Oct 2023

• IC1 Connect the thermistor to a suitable circuit with voltmeter and ammeter Or Connect the thermistor to an ohmmeter
• IC2 Place the thermistor in a water bath Or place the thermistor in a beaker of water
• IC3 Add ice to reduce the water temperature to \(0^{o}C\)
• IC4 Heat the water and use a thermometer to measure the temperature Or Heat the water and use a temperature sensor and datalogger to measure the temperature
• IC5 Determine the resistance R (for each temperature) using R = V/I Or Measure the resistance (for each temperature) by reading from ohmmeter
• IC6 Stir the water (to ensure that the thermistor is at the temperature measured by the thermometer)
• Or Place the thermometer near to the thermistor (to ensure that the thermistor is at the temperature measured by the thermometer)
• Or Stop heating and wait before taking readings
• (to prevent it heating the thermistor)
• Or Switch current off between readings
• Or Read thermometer at eye level

📚 Oct 2022

• The particles are free to move inside the can
• Or Not all the particles will move with simple harmonic motion
• Or Amplitude/frequency/period of oscillation of particles is different to amplitude of can
• Or The particles may continue to move upwards as the can starts moving downwards
• Or The particles may collide with each other
• Or the force on the paint particles is not equal to the force on the can.

📚 Jun 2022

• Not all the energy will be used to increase the temperature of the lead shot Or some energy will be transferred to the surroundings Or not all the lead shot will fall through a distance d
• The method will not be accurate, as it will give a value of c that is too large Or The method will not be accurate as the (measured) temperature change will be too small

📚 Jun 2023

• Some of the energy from the student’s hand is transferred to the oscillating mass and some of the energy is transferred to surroundings
• When the amplitude is a maximum, minimum energy is transferred to surroundings [Accept “at the natural frequency” or “resonance” for when the amplitude is a maximum]
• (In a closed system) total energy is constant so the student is incorrect.

📚 Jan 2023

• (Kinetic) energy is transferred from the car Or (Kinetic energy transferred to the suspension/dampers)
• The energy is dissipated to the surroundings [so the vibration energy decreases]

📚 Oct 2023

• Energy is transferred out of the oscillating system Or energy is dissipated (to surroundings)
• Because work is done by/against resistive forces

📚 Jun 2024

• The motion of the box is (strongly) damped
• Amplitude at resonance is small
• Lead box has a large mass/inertia
• A large force is needed to set box into motion

📚 Jun 2024

• Match the natural frequency (of the dampers) to the driving frequency
• So that there is an efficient / maximum transfer of energy (to the dampers)

📚 Jun 2024

• Work is done (by roller) as oil is forced through the holes
• So energy is transferred from the building (and not returned) Or energy is transferred to the surroundings (and not returned) [Accept “dissipated” for “transferred to surroundings”]

📚 Jun 2022

• IC1 Striking the glass sets the glass into (free) oscillation.
• Or the oscillation is damped and the amplitude (of oscillation) decreases (quickly to zero).
• IC3 Sliding a wet finger around the top of the glass drives/forces the glass/system into oscillation.
• IC4 The driving frequency (produced by the wet finger) is equal/close to the natural frequency (of oscillation) of the glass/system
• IC5 Resonance occurs and there is an efficient/maximum transfer of energy
• IC6 The amplitude (of oscillation) increases (and transfers energy to the air)

📚 Oct 2022

• Period of the tide matches natural period of oscillation of water in the bay [accept references to frequency]
• Efficient/maximum transfer of energy (into water in the bay) Or Resonance occurs
• Amplitude (of tide) increases Or There is a maximum amplitude

📚 Jan 2023

• The car (body) is driven/forced into oscillation at its natural frequency Or The driving/forcing frequency is the same as the natural frequency of the car (body) Or the driving/forcing frequency from the road is the same as the natural frequency (of the car body)
• There is a maximum transfer of energy (to the car body)

📚 2023 Jun

• When the driving frequency is equal to the natural frequency of the mass-spring system
• Resonance occurs
• There is a maximum transfer of energy (to the mass-spring system and the amplitude increases)

📚 2024 Jun

• There is a (resultant) acceleration / force that is proportional to the displacement from the equilibrium position
• and (always) acting towards the equilibrium position

📚 2023 Oct

• There is a (resultant) force that is proportional to the displacement from the equilibrium position
• and (always) acting towards the equilibrium position

📚 2023 Jun

• For an object to move with simple harmonic motion
• there must be an acceleration/(resultant) force that is proportional to the displacement from the equilibrium position
• and (always) acting towards the equilibrium position

📚 2023 Jan

• The star is viewed from two positions at 6 month intervals Or the star is viewed from opposite ends of the diameter of the Earth's orbit about the Sun
• The change in angular position of the star against backdrop of distant/fixed star is measured
• Trigonometry is used to calculate the distance to the star [Do not accept Pythagoras]
• The diameter/radius of the Earth’s orbit about the Sun must be known

📚 2023 Jan

• There is a range of molecular speeds Or Some molecules will be travelling (much) faster than 1900 \(ms^{-1}\)
• So there will be some molecules with a speed greater than the escape velocity Or There will be some molecules with enough kinetic energy to escape

📚 2022 Jan

• \(v \propto \sqrt{\frac{M}{r}}\)
• Within the central region M changes a lot (so v increases) Or Outside the central region M is approximately constant (so v decreases)
• As r increases v reaches a peak value as shown on the graph

📚 2023 Jun

• This cluster has red giant stars on the top right of the diagram
• And white dwarf stars bottom left of diagram
• A young cluster would only have a main sequence Or Red giant stars only occur in the later stages of a star’s evolution Or White dwarf stars only occur in the later stages of a star’s evolution

📚 2023 Oct

• A main sequence star is a star that is fusing hydrogen in its core

📚 2022 Jun

• \(H_{\text{0}}\) is halved (for the same recessional velocity)
• So the (calculated) age of the universe doubles
• OR
• The universe would have taken twice as long to expand to its current size (assuming it expanded at the same rate)
• So the age of the universe is double what was previously thought

📚 2023 Oct

• EITHER
• A straight line through the origin would be consistent with Hubble’s expression
• There is scatter about the line but the points are distributed evenly
• So the expression may be valid (dependent upon MP2)
• OR
• A straight line through the origin would be consistent with Hubble’s expression
• (But) there are OUTLIERS and these are far from the line Or (But) only some of the points are close to the line
• So the expression may not be valid (dependent upon MP2)
• OR
• The gradient of the line is equal to \(H_{\text{0}}\)
• There is scatter about the line, so the value of \(H_{\text{0}}\) is uncertain
• So the expression may not be valid (dependent upon MP2)

📚 2022 Oct

• Very distant galaxies have (very) large red shifts
• So their light has become infrared when it arrives (at the telescope)

📚 2023 Oct

• The light / radiation (received) from the galaxies is red-shifted Or Wavelength of light / radiation (received) from the galaxies was longer than expected

📚 Jan 2024

• IC1 There must be a (very) high temperature (in the core)
• or \(E_{\text{k}}\)]
• IC3 So that nuclei/protons get close enough to fuse
• IC4 Because there is an electrostatic repulsion between nuclei/protons
• IC5 There must be a (very) high density
• IC6 To give a high collision rate to maintain fusion Or To give a high collision rate to maintain high temperature

📚 Jun 2023

• Very high temperature so that the nuclei have sufficient kinetic energy
• Nuclei must overcome electrostatic repulsion/forces [Allow a reference to overcome repulsion/forces due to positively charged nuclei]
• So that the nuclei come close enough to fuse
• Sufficient density so that the collision rate (between nuclei) is high (enough)
• Sufficient collision rate to maintain the (very high) temperature

📚 Jun 2022

• Parallax angle decreases as distance from the Earth increases Or parallax is only suitable for (relatively) close stars
• As parallax angle is too small to measure for distant stars

📚 Oct 2022

• IC1 Use (stellar) parallax to determine distance to a nearby standard
• candle,
• IC2 Measure the intensity of radiation from the standard candle Or Measure λmax and use Wien’s law to determine the (surface) temperature of the standard candle
• IC3 Use inverse square law to calculate the luminosity of the standard candle Or Use the Hertzsprung-Russell diagram to determine the luminosity of the standard candle
• IC4 Locate standard candle (in nearby galaxy)
• IC5 Standard candle has a known luminosity
• IC6 Measure intensity of radiation from the standard candle and use inverse square law to calculate distance to nearby galaxy
• Alternative for IC1, IC2 and IC3:
• IC1 Identify/observe a (Cepheid) variable star
• IC2 Measure the period/frequency of intensity variation
• IC3 Use a known relationship between period and luminosity to calculate the luminosity of the star

📚 Jan 2023

• Identify/locate standard candle (in nearby galaxy)
• Measure intensity of radiation from the standard candle
• Use inverse square law to calculate distance

📚 Jan 2024

• Standard candles are stellar objects with a known luminosity
• Locate a standard candle in the galaxy
• Measure the intensity of the standard candle (on Earth)
• Use the inverse square law to calculate the distance to the standard candle

📚 Jun 2023

• The luminosity of the standard candle is known
• Measure/determine intensity of radiation from V1 [standard candle] [do not accept ‘calculate’]
• Use inverse square law to calculate distance (to cluster)
• Distance is too large (for V1 to be in a nearby cluster) [Must have the idea of being too far away, rather than just being far away]

📚 Jan 2024

• Stars in area P are (massive) main sequence stars
• Stars in area P evolve into area S and stars in area S evolve into area Q [Allow P → S → Q, or arrows on diagram]
• Stars in area S are red giant stars and stars in area Q are white dwarf stars [accept red supergiant for red giant]

📚 Jun 2024

• IC1 Hydrogen fusion occurs in the core of the (main sequence) star
• IC2 Hydrogen (in the core) runs out
• IC3 The rate of fusion decreases and the star contracts
• IC4 The temperature rises (in the core) and fusion of helium begins
• IC5 The star expands (and cools) to form a red giant star
• IC6 (Helium) fusion stops and the star collapses to a white dwarf star Or helium runs out and the star collapses to a white dwarf star

📚 Jan 2023

• The ultimate fate of the universe depends upon the (average) density of the universe Or the (average) density of the universe must be compared with the critical density of the universe
• The amount of dark matter is uncertain (so the average density is uncertain)

📚 Jan 2022

• There must be more mass (than we can observe) [Accept statement that there must be a greater gravitational force]
• There is dark matter present (in the galaxy)

📚 Jan 2023

• Dark matter has mass Or Dark matter exerts a gravitational force
• Dark matter does not emit electromagnetic radiation

📚 Jun 2024

• The actual period is (much) smaller than the calculated value
• So the mass of the galaxy must be greater than 8.0 × 10^11 solar masses [accept the given mass for the numerical value] Or the gravitational force on the star must be bigger (than assumed)
• There must be matter that does not emit em-radiation Or There must be matter that we cannot detect via em-radiation [Accept “there must be matter that we cannot see”]
• (This suggests that) there is dark matter

📚 Oct 2023

• Work would be done on the asteroid by frictional forces Or Drag/friction causes heating (of the asteroid)
• Asteroid burns up

📚 Jan 2024

• The astronauts must experience a centripetal force as they orbit the Earth Or The weight of the astronaut acts as a centripetal force Or The astronauts are in free fall as they orbit the Earth
• They do not experience (normal) contact forces

📚 Jun 2024

• \(V_{\text{grav}} = -\frac{GM}{r}\), so gravitational potential \(\propto\frac{1}{r}\) Or \(V_{\text{grav}} = -\frac{GM}{r}\) and \(G\) and \(M\) are constant
• The equipotential surfaces become further apart with increasing distance (from Earth)

📚 Jun 2022

• Upthrust on airship is equal to the weight of the airship (so) resultant force on the airship is zero (so airship floats in the air)
• Or (vertically) balanced forces act on the airship

📚 Jun 2022

• The resultant force on the man = \(mg – R\) where \(R\) is the (normal) contact force from the board
• R decreases as his displacement (from the equilibrium position) increases
• Man loses contact with board when \(R = 0\) Or Man loses contact with board when resultant force on man is equal to his weight
• OR
• Acceleration (for SHM) increases as displacement increases
• Maximum (downward) acceleration of man is \(g\)
• Man loses contact with board when acceleration of the board is equal to \(g\)