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<!DOCTYPE html>
<html>
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<title>IAL WPH15 Past Paper By Topic</title>
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<h1 id="physics-unit-5">Physics Unit 5</h1>
<details style="margin-left: 0px;">
<summary class="category"><strong>5.4 Nuclear Decay</strong></summary>
<details style="margin-left: 20px;">
<summary class="subcategory">Definition of fission</summary>
<details style="margin-left: 40px;">
<summary class="question"><strong>State</strong> what is meant by fission (1)</summary>
<p class="text" style="margin-left: 60px;">๐ Oct 2022</p>
<ul style="margin-left: 60px;">
<li>A massive nucleus splits into two (or more) smaller nuclei/fragments (of roughly equal mass and some
neutrons)</li>
</ul>
</details>
</details>
<details style="margin-left: 20px;">
<summary class="subcategory">Application of radioactive substances</summary>
<details style="margin-left: 40px;">
<summary class="question">The isotope 32P is injected into a person and collects in the tumour. Radiation is
detected outside the personโs body. 32P is a positron emitter with a half-life of almost fifteen days.
<strong>Explain</strong> why 32P is suitable for this procedure (4)</summary>
<p class="text" style="margin-left: 60px;">๐ Oct 2022</p>
<ul style="margin-left: 60px;">
<li>Positrons annihilate with electrons to produce gamma radiation</li>
<li>Gamma radiation can penetrate the body</li>
<li>Half life is long enough to allow the procedure to be performed</li>
<li>Half life is short enough to avoid unnecessarily large radiation dose</li>
</ul>
</details>
</details>
<details style="margin-left: 20px;">
<summary class="subcategory">Cloud chamber, bubble chamber tracks</summary>
<details style="margin-left: 40px;">
<summary class="question">A student makes the following observations: the alpha particle tracks are thick and
straight; the beta particle tracks are thin and twisted. <strong>Explain</strong> these observations (4)
</summary>
<p class="text" style="margin-left: 60px;">๐ Jun 2023</p>
<ul style="margin-left: 60px;">
<li>The thickness of the track related to the ionising ability of the particle (not its mass)</li>
<li>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]</li>
<li>The shape of the track related to the mass of the particle (not its ionising ability)</li>
<li>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]</li>
</ul>
</details>
</details>
<details style="margin-left: 20px;">
<summary class="subcategory">Binding energy per nucleus vs stability</summary>
<details style="margin-left: 40px;">
<summary class="question">The binding energy per nucleon of helium is relatively large.
<strong>Explain</strong> why this makes the helium nucleus particularly stable (2)</summary>
<p class="text" style="margin-left: 60px;">๐ Jan 2024</p>
<ul style="margin-left: 60px;">
<li>The binding energy per nucleon is the energy required to remove a nucleon from the nucleus</li>
<li>Large energy is required to break the helium nucleus apart</li>
<li>Decay products (of helium) have a lower binding energy per nucleon</li>
</ul>
</details>
</details>
<details style="margin-left: 20px;">
<summary class="subcategory">Conservation of momentum</summary>
<details style="margin-left: 40px;">
<summary class="question"><strong>Explain</strong> why not all of the energy from the decay is released as
kinetic energy of the alpha particle (2)</summary>
<p class="text" style="margin-left: 60px;">๐ Jun 2022</p>
<ul style="margin-left: 60px;">
<li>Momentum must be conserved (in the decay)</li>
<li>The lead nucleus must recoil after the decay Or the lead nucleus moves in the opposite direction to the
alpha particle</li>
</ul>
</details>
<details style="margin-left: 40px;">
<summary class="question"><strong>Explain</strong> why the emission of an antineutrino in the decay leads to a
range of energies for the beta- particles (2)</summary>
<p class="text" style="margin-left: 60px;">๐ Oct 2022</p>
<ul style="margin-left: 60px;">
<li>Momentum is conserved (so the Ba nucleus recoils)</li>
<li>Energy released is shared (randomly) between the ฮฒโ and ฮฝฬ
Or the energy is shared between the 3
particles in the decay</li>
</ul>
</details>
<details style="margin-left: 40px;">
<summary class="question"><strong>Explain</strong> why the alpha particle must have an energy greater than the
minimum energy for the reaction to take place (2)</summary>
<p class="text" style="margin-left: 60px;">๐ Oct 2023</p>
<ul style="margin-left: 60px;">
<li>Momentum (and energy) is conserved</li>
<li>(So) products must have \(E_{\text{k}}\) / momentum after the reaction (as the alpha particle has
momentum before the reaction)</li>
</ul>
</details>
</details>
<details style="margin-left: 20px;">
<summary class="subcategory">Energy released during fission / fusion</summary>
<details style="margin-left: 40px;">
<summary class="question"><strong>Explain</strong> why energy is released when a nucleus undergoes fission (2)
</summary>
<p class="text" style="margin-left: 60px;">๐ Jan 2024</p>
<ul style="margin-left: 60px;">
<li>A large nucleus splits (into two nuclei plus neutrons)</li>
<li>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)</li>
</ul>
</details>
<details style="margin-left: 40px;">
<summary class="question"><strong>Explain</strong> why energy is released when hydrogen nuclei fuse to form
helium nuclei (2)</summary>
<p class="text" style="margin-left: 60px;">๐ Jun 2023</p>
<ul style="margin-left: 60px;">
<li>In the fusion process mass decreases</li>
<li>So energy is released according to \(โE = c^{2}โm\) Or energy is released to conserve mass-energy Or
binding energy per nucleon increases</li>
</ul>
</details>
</details>
<details style="margin-left: 20px;">
<summary class="subcategory">Range of alpha / beta / gamma radiation</summary>
<details style="margin-left: 40px;">
<summary class="question"><strong>State</strong> why alpha radiation will not affect the recorded count rate
(1)</summary>
<p class="text" style="margin-left: 60px;">๐ Jun 2024</p>
<ul style="margin-left: 60px;">
<li>The alpha radiation will not penetrate the lead</li>
<li>Or The lead will absorb the alpha radiation</li>
</ul>
</details>
<details style="margin-left: 40px;">
<summary class="question"><strong>Explain</strong> which type of radiation is emitted from the source. You
should refer to the penetration of each type of radiation through each sheet of absorber (4)</summary>
<p class="text" style="margin-left: 60px;">๐ Jan 2024</p>
<ul style="margin-left: 60px;">
<li>Alpha radiation would not pass through the sheet of paper</li>
<li>No change in count rate when paper placed (between source and GM tube), so there canโt be any alpha
radiation</li>
<li>There canโt be any gamma radiation, as gamma radiation would pass through the aluminium sheet Or There
canโt be any gamma radiation, as count rate decreases to background with aluminium sheet.</li>
<li>It must be beta radiation as beta radiation would not pass through the aluminium sheet.</li>
</ul>
</details>
</details>
<details style="margin-left: 20px;">
<summary class="subcategory">Core practical: measuring radioactivity</summary>
<details style="margin-left: 40px;">
<summary class="question"><strong>Explain</strong> one modification to her method that would give a more
accurate value for the count rate (2)</summary>
<p class="text" style="margin-left: 60px;">๐ Jun 2024</p>
<ul style="margin-left: 60px;">
<li>EITHER</li>
<li>Determine the background count (rate)</li>
<li>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</li>
<li>OR</li>
<li>Record the count for a longer time interval Or Record the count more than once and calculate a mean
value</li>
<li>This will reduce the effect of random variation on the count rate Or this will decrease the percentage
uncertainty</li>
</ul>
</details>
</details>
</details>
<details style="margin-left: 0px;">
<summary class="category"><strong>5.3 Thermodynamics</strong></summary>
<details style="margin-left: 20px;">
<summary class="subcategory">The kinetic model</summary>
<details style="margin-left: 40px;">
<summary class="question"><strong>Explain</strong> why the pressure of the air inside the scuba tank increases
as the temperature increases. Your answer should refer to the motion of the air molecules (6)</summary>
<p class="text" style="margin-left: 60px;">๐ Jan 2023</p>
<ul style="margin-left: 60px;">
<li>IC1 As the temperature increases the (average) kinetic energy of the (air) molecules increases</li>
<li>IC2 So mean/average speed of the air molecules increases</li>
<li>IC3 The (average/mean) change of momentum of air molecules when colliding with the tank/walls increases
</li>
<li>IC4 The rate of collision of air molecules with the tank/walls increases</li>
<li>IC5 The rate of change of momentum increases and so the force on the tank/walls, increases</li>
<li>IC6 The pressure (exerted by the gas) increases, since p = F/A</li>
</ul>
</details>
</details>
<details style="margin-left: 20px;">
<summary class="subcategory">Melting</summary>
<details style="margin-left: 40px;">
<summary class="question">*<strong>Describe</strong> how the internal energy of the wax changes as the wax
cools. You should refer to the energy of the wax molecules as the liquid wax cools and becomes solid, and
the solid wax cools (6)</summary>
<p class="text" style="margin-left: 60px;">๐ Jun 2023</p>
<ul style="margin-left: 60px;">
<li>IC1 The internal energy of the wax decreases during cooling Or The internal energy of the wax decreases
as time passes</li>
<li>IC2 The internal energy of the wax is the sum of potential energy and kinetic energy of the molecules
</li>
<li>IC3 As the temperature of the wax decreases, the (molecular) kinetic energy</li>
<li>decreases</li>
<li>IC4 Between times X and Y the (liquid wax is solidifying and the molecular) potential energy decreases
</li>
<li>IC5 Between times X and Y the temperature is constant and so there is no change in (molecular) kinetic
energy</li>
<li>IC6 At time Y the wax has solidified</li>
</ul>
</details>
</details>
<details style="margin-left: 20px;">
<summary class="subcategory">Boiling</summary>
<details style="margin-left: 40px;">
<summary class="question"><strong>Explain</strong> why the liquid nitrogen boiled when the banana as submerged
in the liquid nitrogen (2)</summary>
<p class="text" style="margin-left: 60px;">๐ Jan 2024</p>
<ul style="margin-left: 60px;">
<li>Energy is transferred from banana to liquid nitrogen</li>
<li>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)</li>
</ul>
</details>
</details>
<details style="margin-left: 20px;">
<summary class="subcategory">Core practical: determining specific heat capacity</summary>
<details style="margin-left: 40px;">
<summary class="question">A heater is used to increase the temperature of the water. <strong>State</strong>
why the amount of energy supplied by the heater will be different from the value of delta R calculated in
(a) (1)</summary>
<p class="text" style="margin-left: 60px;">๐ Jan 2023</p>
<ul style="margin-left: 60px;">
<li>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</li>
</ul>
</details>
</details>
<details style="margin-left: 20px;">
<summary class="subcategory">Core practical: calibration of thermistor</summary>
<details style="margin-left: 40px;">
<summary class="question">*A student is planning an experiment to investigate how the resistance of a
thermistor changes with temperature. The student wants to use the temperature range 0dC to 100dC.
<strong>Describe</strong> a method the student could use to determine values of resistance and temperature
over this range. You should include one precaution the student should take to ensure accurate measurements.
You do not need to draw a circuit diagram. (6)</summary>
<p class="text" style="margin-left: 60px;">๐ Oct 2023</p>
<ul style="margin-left: 60px;">
<li>IC1 Connect the thermistor to a suitable circuit with voltmeter and ammeter Or Connect the thermistor to
an ohmmeter</li>
<li>IC2 Place the thermistor in a water bath Or place the thermistor in a beaker of water</li>
<li>IC3 Add ice to reduce the water temperature to \(0^{o}C\)</li>
<li>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</li>
<li>IC5 Determine the resistance R (for each temperature) using R = V/I Or Measure the resistance (for each
temperature) by reading from ohmmeter</li>
<li>IC6 Stir the water (to ensure that the thermistor is at the temperature measured by the thermometer)
</li>
<li>Or Place the thermometer near to the thermistor (to ensure that the thermistor is at the temperature
measured by the thermometer)</li>
<li>Or Stop heating and wait before taking readings</li>
<li>(to prevent it heating the thermistor)</li>
<li>Or Switch current off between readings</li>
<li>Or Read thermometer at eye level</li>
</ul>
</details>
</details>
</details>
<details style="margin-left: 0px;">
<summary class="category"><strong>5.5 Oscillations</strong></summary>
<details style="margin-left: 20px;">
<summary class="subcategory">Maximum acceleration of particles in a container</summary>
<details style="margin-left: 40px;">
<summary class="question"><strong>Suggest</strong> why the particles of paint in the can will experience a
maximum acceleration that is different from the answer to (ii) (1)</summary>
<p class="text" style="margin-left: 60px;">๐ Oct 2022</p>
<ul style="margin-left: 60px;">
<li>The particles are free to move inside the can</li>
<li>Or Not all the particles will move with simple harmonic motion</li>
<li>Or Amplitude/frequency/period of oscillation of particles is different to amplitude of can</li>
<li>Or The particles may continue to move upwards as the can starts moving downwards</li>
<li>Or The particles may collide with each other</li>
<li>Or the force on the paint particles is not equal to the force on the can.</li>
</ul>
</details>
</details>
<details style="margin-left: 20px;">
<summary class="subcategory">Energy Conservation</summary>
<details style="margin-left: 40px;">
<summary class="question">The teacher turns the tube upside down, and the lead shot falls through a distance
d. The teacher repeats this N times and measures the final temperature of the lead shot. The change in
temperature delta theta off the lead shot is calculated. The teacher uses d, N, delta theta to determine a
val for the s.h.c. of the lead. <strong>Assess</strong> whether this method would produce an accurate value
for c (2)</summary>
<p class="text" style="margin-left: 60px;">๐ Jun 2022</p>
<ul style="margin-left: 60px;">
<li>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</li>
<li>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</li>
</ul>
</details>
<details style="margin-left: 40px;">
<summary class="question">The student makes the following conclusion: โAs the frequency is increased, the
amplitude of the mass increases to a maximum, so energy conservation does not apply to this situation.โ
<strong>Explain</strong> whether her conclusion is correct (3)</summary>
<p class="text" style="margin-left: 60px;">๐ Jun 2023</p>
<ul style="margin-left: 60px;">
<li>Some of the energy from the studentโs hand is transferred to the oscillating mass and some of the energy
is transferred to surroundings</li>
<li>When the amplitude is a maximum, minimum energy is transferred to surroundings [Accept โat the natural
frequencyโ or โresonanceโ for when the amplitude is a maximum]</li>
<li>(In a closed system) total energy is constant so the student is incorrect.</li>
</ul>
</details>
</details>
<details style="margin-left: 20px;">
<summary class="subcategory">Damping</summary>
<details style="margin-left: 40px;">
<summary class="question"><strong>Explain</strong> how damping reduces the large amplitude of vibration of the
car on its suspension (2)</summary>
<p class="text" style="margin-left: 60px;">๐ Jan 2023</p>
<ul style="margin-left: 60px;">
<li>(Kinetic) energy is transferred from the car Or (Kinetic energy transferred to the suspension/dampers)
</li>
<li>The energy is dissipated to the surroundings [so the vibration energy decreases]</li>
</ul>
</details>
<details style="margin-left: 40px;">
<summary class="question"><strong>Explain</strong> why the maximum velocity of the oscillating mass decreased
over time (2)</summary>
<p class="text" style="margin-left: 60px;">๐ Oct 2023</p>
<ul style="margin-left: 60px;">
<li>Energy is transferred out of the oscillating system Or energy is dissipated (to surroundings)</li>
<li>Because work is done by/against resistive forces</li>
</ul>
</details>
<details style="margin-left: 40px;">
<summary class="question">When the building oscillates, the floor moves but the lead box tends to remain at
rest. <strong>Suggest</strong> why the lead box tends to remain at rest (2)</summary>
<p class="text" style="margin-left: 60px;">๐ Jun 2024</p>
<ul style="margin-left: 60px;">
<li>The motion of the box is (strongly) damped</li>
<li>Amplitude at resonance is small</li>
<li>Lead box has a large mass/inertia</li>
<li>A large force is needed to set box into motion</li>
</ul>
</details>
<details style="margin-left: 40px;">
<summary class="question">When the wind blows at a certain speed, the building oscillates with a frequency of
0.17 Hz
<strong>Explain</strong> why the damper system should be designed to oscillate at this frequency (2)
</summary>
<p class="text" style="margin-left: 60px;">๐ Jun 2024</p>
<ul style="margin-left: 60px;">
<li>Match the natural frequency (of the dampers) to the driving frequency</li>
<li>So that there is an efficient / maximum transfer of energy (to the dampers)</li>
</ul>
</details>
<details style="margin-left: 40px;">
<summary class="question">As the floor moves, the rollers force oil through holes in the steel plate.
<strong>Explain</strong> why this reduces the amplitude of oscillation of the building (2)</summary>
<p class="text" style="margin-left: 60px;">๐ Jun 2024</p>
<ul style="margin-left: 60px;">
<li>Work is done (by roller) as oil is forced through the holes</li>
<li>So energy is transferred from the building (and not returned) Or energy is transferred to the
surroundings (and not returned) [Accept โdissipatedโ for โtransferred to surroundingsโ]</li>
</ul>
</details>
</details>
<details style="margin-left: 20px;">
<summary class="subcategory">Resonance</summary>
<details style="margin-left: 40px;">
<summary class="question">* A teacher is teaching her class about the phenomenon of resonance. To do this, she
uses a drinking glass to produce sound in two different ways. When the glass is gently struck, the glass
emits sound for a short time. When a wet finger is slid around the top of the glass, it is possible to
produce a loud continuous sound. <strong>Explain</strong> these observations (6)</summary>
<p class="text" style="margin-left: 60px;">๐ Jun 2022</p>
<ul style="margin-left: 60px;">
<li>IC1 Striking the glass sets the glass into (free) oscillation.</li>
<li>Or the oscillation is damped and the amplitude (of oscillation) decreases (quickly to zero).</li>
<li>IC3 Sliding a wet finger around the top of the glass drives/forces the glass/system into oscillation.
</li>
<li>IC4 The driving frequency (produced by the wet finger) is equal/close to the natural frequency (of
oscillation) of the glass/system</li>
<li>IC5 Resonance occurs and there is an efficient/maximum transfer of energy</li>
<li>IC6 The amplitude (of oscillation) increases (and transfers energy to the air)</li>
</ul>
</details>
<details style="margin-left: 40px;">
<summary class="question"><strong>Explain</strong> why unusually high tides are observed in the bay (3)
</summary>
<p class="text" style="margin-left: 60px;">๐ Oct 2022</p>
<ul style="margin-left: 60px;">
<li>Period of the tide matches natural period of oscillation of water in the bay [accept references to
frequency]</li>
<li>Efficient/maximum transfer of energy (into water in the bay) Or Resonance occurs</li>
<li>Amplitude (of tide) increases Or There is a maximum amplitude</li>
</ul>
</details>
<details style="margin-left: 40px;">
<summary class="question"><strong>Explain</strong> why the amplitude of vibration increases at a particular
speed (2)</summary>
<p class="text" style="margin-left: 60px;">๐ Jan 2023</p>
<ul style="margin-left: 60px;">
<li>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)</li>
<li>There is a maximum transfer of energy (to the car body)</li>
</ul>
</details>
<details style="margin-left: 40px;">
<summary class="question">The student increases the frequency at which she oscillates her hand. She keeps the
amplitude of oscillation of her hand constant. She observes that the amplitude of the oscillation of the
mass increases to a maximum and then decreases. <strong>Explain</strong> this observation. (3)</summary>
<p class="text" style="margin-left: 60px;">๐ 2023 Jun</p>
<ul style="margin-left: 60px;">
<li>When the driving frequency is equal to the natural frequency of the mass-spring system</li>
<li>Resonance occurs</li>
<li>There is a maximum transfer of energy (to the mass-spring system and the amplitude increases)</li>
</ul>
</details>
</details>
<details style="margin-left: 20px;">
<summary class="subcategory">Definition of simple harmonic motion</summary>
<details style="margin-left: 40px;">
<summary class="question"><strong>State</strong> what is meant by simple harmonic motion (2)</summary>
<p class="text" style="margin-left: 60px;">๐ 2024 Jun</p>
<ul style="margin-left: 60px;">
<li>There is a (resultant) acceleration / force that is proportional to the displacement from the
equilibrium position</li>
<li>and (always) acting towards the equilibrium position</li>
</ul>
</details>
<details style="margin-left: 40px;">
<summary class="question">
<strong>Explain</strong> why the motion of the mass was simple harmonic motion (2)</summary>
<p class="text" style="margin-left: 60px;">๐ 2023 Oct</p>
<ul style="margin-left: 60px;">
<li>There is a (resultant) force that is proportional to the displacement from the equilibrium position</li>
<li>and (always) acting towards the equilibrium position</li>
<li></li>
</ul>
</details>
<details style="margin-left: 40px;">
<summary class="question"><strong>State</strong> what is meant by simple harmonic motion (2)</summary>
<p class="text" style="margin-left: 60px;">๐ 2023 Jun</p>
<ul style="margin-left: 60px;">
<li>For an object to move with simple harmonic motion</li>
<li>there must be an acceleration/(resultant) force that is proportional to the displacement from the
equilibrium position</li>
<li>and (always) acting towards the equilibrium position</li>
</ul>
</details>
</details>
</details>
<details style="margin-left: 0px;">
<summary class="category"><strong>5.6 Astrophysics and Cosmology</strong></summary>
<details style="margin-left: 20px;">
<summary class="subcategory">Determination of stellar parallax</summary>
<details style="margin-left: 40px;">
<summary class="question"><strong>Describe</strong> how stellar parallax is used by astronomers (4)</summary>
<p class="text" style="margin-left: 60px;">๐ 2023 Jan</p>
<ul style="margin-left: 60px;">
<li>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</li>
<li>The change in angular position of the star against backdrop of distant/fixed star is measured</li>
<li>Trigonometry is used to calculate the distance to the star [Do not accept Pythagoras]</li>
<li>The diameter/radius of the Earthโs orbit about the Sun must be known</li>
</ul>
</details>
</details>
<details style="margin-left: 20px;">
<summary class="subcategory">Data inferences</summary>
<details style="margin-left: 40px;">
<summary class="question"><strong>Explain</strong> why hydrogen gas is no longer a large proportion of the gas
in the Earthโs atmosphere. No further calculation is necessary. (2)</summary>
<p class="text" style="margin-left: 60px;">๐ 2023 Jan</p>
<ul style="margin-left: 60px;">
<li>There is a range of molecular speeds Or Some molecules will be travelling (much) faster than 1900
\(ms^{-1}\)</li>
<li>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</li>
</ul>
</details>
<details style="margin-left: 40px;">
<summary class="question">Astronomers think that there is a very large concentration of stars in the central
region of the galaxy. Outside this central region the concentration of stars is very much less. All stars in
the galaxy are rotating about its centre. It can be shown that the velocity v of a star a distance r from
the centre of the galaxy is given by the expression \(v = \sqrt{\frac{GM}{r}}\).
The graph shows how astronomers expect v to vary with r. <strong>Explain</strong> how the expression gives
the variation of v with r shown in the graph (3)</summary>
<p class="text" style="margin-left: 60px;">๐ 2022 Jan</p>
<ul style="margin-left: 60px;">
<li>\(v \propto \sqrt{\frac{M}{r}}\)</li>
<li>Within the central region M changes a lot (so v increases) Or Outside the central region M is
approximately constant (so v decreases)</li>
<li>As r increases v reaches a peak value as shown on the graph</li>
</ul>
</details>
</details>
<details style="margin-left: 20px;">
<summary class="subcategory">H-R diagram and age of star</summary>
<details style="margin-left: 40px;">
<summary class="question"><strong>Explain</strong> how this H-R diagram shows that the star cluster is not a
young star cluster. You should refer to groups of stars and their positions on this diagram (3)</summary>
<p class="text" style="margin-left: 60px;">๐ 2023 Jun</p>
<ul style="margin-left: 60px;">
<li>This cluster has red giant stars on the top right of the diagram</li>
<li>And white dwarf stars bottom left of diagram</li>
<li>A young cluster would only have a main sequence Or Red giant stars only occur in the later stages of a
starโs evolution Or White dwarf stars only occur in the later stages of a starโs evolution</li>
</ul>
</details>
</details>
<details style="margin-left: 20px;">
<summary class="subcategory">Definition of main sequence star</summary>
<details style="margin-left: 40px;">
<summary class="question"><strong>State</strong> what is meant by a main sequence star (1)</summary>
<p class="text" style="margin-left: 60px;">๐ 2023 Oct</p>
<ul style="margin-left: 60px;">
<li>A main sequence star is a star that is fusing hydrogen in its core</li>
</ul>
</details>
</details>
<details style="margin-left: 20px;">
<summary class="subcategory">Hubbleโs law</summary>
<details style="margin-left: 40px;">
<summary class="question">In the 1950s, astronomers realised that they had made an error in their
determination of distances to galaxies. Galaxies are twice as far away as astronomers had previously
thought. <strong>Explain</strong> how this changed the age of the universe as calculated by astronomers (2)
</summary>
<p class="text" style="margin-left: 60px;">๐ 2022 Jun</p>
<ul style="margin-left: 60px;">
<li>\(H_{\text{0}}\) is halved (for the same recessional velocity)</li>
<li>So the (calculated) age of the universe doubles</li>
<li> OR</li>
<li>The universe would have taken twice as long to expand to its current size (assuming it expanded at the
same rate)</li>
<li>So the age of the universe is double what was previously thought</li>
</ul>
</details>
<details style="margin-left: 40px;">
<summary class="question"><strong>Assess</strong> the validity of Hubbleโs expression based on the data shown
(3)</summary>
<p class="text" style="margin-left: 60px;">๐ 2023 Oct</p>
<ul style="margin-left: 60px;">
<li>EITHER</li>
<li>A straight line through the origin would be consistent with Hubbleโs expression</li>
<li>There is scatter about the line but the points are distributed evenly</li>
<li>So the expression may be valid (dependent upon MP2)</li>
<li>OR</li>
<li>A straight line through the origin would be consistent with Hubbleโs expression</li>
<li>(But) there are OUTLIERS and these are far from the line Or (But) only some of the points are close to
the line</li>
<li>So the expression may not be valid (dependent upon MP2)</li>
<li>OR</li>
<li>The gradient of the line is equal to \(H_{\text{0}}\)</li>
<li>There is scatter about the line, so the value of \(H_{\text{0}}\) is uncertain</li>
<li>So the expression may not be valid (dependent upon MP2)</li>
</ul>
</details>
</details>
<details style="margin-left: 20px;">
<summary class="subcategory">Red shift</summary>
<details style="margin-left: 40px;">
<summary class="question">The recently launched James Webb Space Telescope is designed to operate in the
infrared region of the spectrum. <strong>Explain</strong> why this will be helpful for studying very distant
galaxies (2)</summary>
<p class="text" style="margin-left: 60px;">๐ 2022 Oct</p>
<ul style="margin-left: 60px;">
<li>Very distant galaxies have (very) large red shifts</li>
<li>So their light has become infrared when it arrives (at the telescope)</li>
</ul>
</details>
<details style="margin-left: 40px;">
<summary class="question"><strong>State</strong> how astronomers knew that galaxies were moving away from the
Earth. (1)</summary>
<p class="text" style="margin-left: 60px;">๐ 2023 Oct</p>
<ul style="margin-left: 60px;">
<li>The light / radiation (received) from the galaxies is red-shifted Or Wavelength of light / radiation
(received) from the galaxies was longer than expected</li>
</ul>
</details>
</details>
<details style="margin-left: 20px;">
<summary class="subcategory">Conditions for fusion (in a star)</summary>
<details style="margin-left: 40px;">
<summary class="question">*<strong>Explain</strong> the conditions required to bring about and maintain fusion
in a main sequence star (6)</summary>
<p class="text" style="margin-left: 60px;">๐ Jan 2024</p>
<ul style="margin-left: 60px;">
<li>IC1 There must be a (very) high temperature (in the core)</li>
<li>or \(E_{\text{k}}\)]</li>
<li>IC3 So that nuclei/protons get close enough to fuse</li>
<li>IC4 Because there is an electrostatic repulsion between nuclei/protons</li>
<li>IC5 There must be a (very) high density</li>
<li>IC6 To give a high collision rate to maintain fusion Or To give a high collision rate to maintain high
temperature</li>
</ul>
</details>
<details style="margin-left: 40px;">
<summary class="question">To achieve fusion in the ITER, a hot plasma is used. The plasma must be - at an
extremely high temperature; - have sufficient density for fusion. <strong>Explain</strong> why these two
conditions must be met (4)</summary>
<p class="text" style="margin-left: 60px;">๐ Jun 2023</p>
<ul style="margin-left: 60px;">
<li>Very high temperature so that the nuclei have sufficient kinetic energy</li>
<li>Nuclei must overcome electrostatic repulsion/forces [Allow a reference to overcome repulsion/forces due
to positively charged nuclei]</li>
<li>So that the nuclei come close enough to fuse</li>
<li>Sufficient density so that the collision rate (between nuclei) is high (enough)</li>
<li>Sufficient collision rate to maintain the (very high) temperature</li>
</ul>
</details>
</details>
<details style="margin-left: 20px;">
<summary class="subcategory">Parallax angles</summary>
<details style="margin-left: 40px;">
<summary class="question"><strong>Explain</strong> why parallax measurements can only be used to determine the
distances to a relatively small number of stars (2)</summary>
<p class="text" style="margin-left: 60px;">๐ Jun 2022</p>
<ul style="margin-left: 60px;">
<li>Parallax angle decreases as distance from the Earth increases Or parallax is only suitable for
(relatively) close stars</li>
<li>As parallax angle is too small to measure for distant stars</li>
</ul>
</details>
</details>
<details style="margin-left: 20px;">
<summary class="subcategory">Standard candles</summary>
<details style="margin-left: 40px;">
<summary class="question">*The average distance between galaxies is many times greater than the size of our
galaxy. Astronomers use standard candles to determine the distances to other galaxies.
<strong>Describe</strong> how astronomers determine the luminosity of a standard candle and can use this to
determine the distance to a nearby galaxy (6)</summary>
<p class="text" style="margin-left: 60px;">๐ Oct 2022</p>
<ul style="margin-left: 60px;">
<li>IC1 Use (stellar) parallax to determine distance to a nearby standard</li>
<li>candle,</li>
<li>IC2 Measure the intensity of radiation from the standard candle Or Measure ฮปmax and use Wienโs law to
determine the (surface) temperature of the standard candle</li>
<li>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</li>
<li>IC4 Locate standard candle (in nearby galaxy)</li>
<li>IC5 Standard candle has a known luminosity</li>
<li>IC6 Measure intensity of radiation from the standard candle and use inverse square law to calculate
distance to nearby galaxy</li>
<li>Alternative for IC1, IC2 and IC3:</li>
<li>IC1 Identify/observe a (Cepheid) variable star</li>
<li>IC2 Measure the period/frequency of intensity variation</li>
<li>IC3 Use a known relationship between period and luminosity to calculate the luminosity of the star</li>
<li></li>
</ul>
</details>
<details style="margin-left: 40px;">
<summary class="question"><strong>Describe</strong> how standard candles can be used to determine the distance
to nearby galaxies (3)</summary>
<p class="text" style="margin-left: 60px;">๐ Jan 2023</p>
<ul style="margin-left: 60px;">
<li>Identify/locate standard candle (in nearby galaxy)</li>
<li>Measure intensity of radiation from the standard candle</li>
<li>Use inverse square law to calculate distance</li>
</ul>
</details>
<details style="margin-left: 40px;">
<summary class="question"><strong>Describe</strong> how standard candles can be used to determine the distance
to galaxies (4)</summary>
<p class="text" style="margin-left: 60px;">๐ Jan 2024</p>
<ul style="margin-left: 60px;">
<li>Standard candles are stellar objects with a known luminosity</li>
<li>Locate a standard candle in the galaxy</li>
<li>Measure the intensity of the standard candle (on Earth)</li>
<li>Use the inverse square law to calculate the distance to the standard candle</li>
</ul>
</details>
<details style="margin-left: 40px;">
<summary class="question"><strong>Describe</strong> how measurements of this standard candle (V1) could
demonstrate that the Andromeda Nebula is not a nearby star cluster (4)</summary>
<p class="text" style="margin-left: 60px;">๐ Jun 2023</p>
<ul style="margin-left: 60px;">
<li>The luminosity of the standard candle is known</li>
<li>Measure/determine intensity of radiation from V1 [standard candle] [do not accept โcalculateโ]</li>
<li>Use inverse square law to calculate distance (to cluster)</li>
<li>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]</li>
</ul>
</details>
</details>
<details style="margin-left: 20px;">
<summary class="subcategory">Life cycle of a star</summary>
<details style="margin-left: 40px;">
<summary class="question"><strong>Describe</strong> a possible evolutionary path for stars originally in area
P. For each stage in the path, you should refer to the type of star (3)</summary>
<p class="text" style="margin-left: 60px;">๐ Jan 2024</p>
<ul style="margin-left: 60px;">
<li>Stars in area P are (massive) main sequence stars</li>
<li>Stars in area P evolve into area S and stars in area S evolve into area Q [Allow P โ S โ Q, or arrows on
diagram]</li>
<li>Stars in area S are red giant stars and stars in area Q are white dwarf stars [accept red supergiant for
red giant]</li>
</ul>
</details>
<details style="margin-left: 40px;">
<summary class="question">*Main sequence stars evolve into red giant stars. Red giant stars eventually become
white dwarf stars. <strong>Explain</strong> this evolutionary sequence. You should refer to the fusion
processes occurring in the star. (6)</summary>
<p class="text" style="margin-left: 60px;">๐ Jun 2024</p>
<ul style="margin-left: 60px;">
<li>IC1 Hydrogen fusion occurs in the core of the (main sequence) star</li>
<li>IC2 Hydrogen (in the core) runs out</li>
<li>IC3 The rate of fusion decreases and the star contracts</li>
<li>IC4 The temperature rises (in the core) and fusion of helium begins</li>
<li>IC5 The star expands (and cools) to form a red giant star</li>
<li>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</li>
</ul>
</details>
</details>
<details style="margin-left: 20px;">
<summary class="subcategory">Fate of the universe</summary>
<details style="margin-left: 40px;">
<summary class="question">The ultimate fate of our universe is uncertain.
<strong>Explain</strong> how the existence of dark matter contributes to this uncertainty (2)</summary>
<p class="text" style="margin-left: 60px;">๐ Jan 2023</p>
<ul style="margin-left: 60px;">
<li>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</li>
<li>The amount of dark matter is uncertain (so the average density is uncertain)</li>
</ul>
</details>
</details>
<details style="margin-left: 20px;">
<summary class="subcategory">Dark matter</summary>
<details style="margin-left: 40px;">
<summary class="question">The observed variation of v with r has been added to produce the graph below.
<strong>Suggest</strong> why the โobservedโ velocity varies as shown. (2)</summary>
<p class="text" style="margin-left: 60px;">๐ Jan 2022</p>
<ul style="margin-left: 60px;">
<li>There must be more mass (than we can observe) [Accept statement that there must be a greater
gravitational force]</li>
<li>There is dark matter present (in the galaxy)</li>
<li></li>
</ul>
</details>
<details style="margin-left: 40px;">
<summary class="question"><strong>Describe</strong> what is meant by dark matter (2)</summary>
<p class="text" style="margin-left: 60px;">๐ Jan 2023</p>
<ul style="margin-left: 60px;">
<li>Dark matter has mass Or Dark matter exerts a gravitational force</li>
<li>Dark matter does not emit electromagnetic radiation</li>
</ul>
</details>
<details style="margin-left: 40px;">
<summary class="question">The orbital period of the star is actually 6.0 * 10^7s (smaller).
<strong>Deduce</strong> what this tells us about our galaxy. Assume that the value for the distance of the
star from the centre of our galaxy is correct (4)</summary>
<p class="text" style="margin-left: 60px;">๐ Jun 2024</p>
<ul style="margin-left: 60px;">
<li>The actual period is (much) smaller than the calculated value</li>
<li>So the mass of the galaxy must be greater than 8.0 ร 10^11 solar masses [accept the given mass for the
numerical value] Or the gravitational force on the star must be bigger (than assumed)</li>
<li>There must be matter that does not emit em-radiation Or There must be matter that we cannot detect via
em-radiation [Accept โthere must be matter that we cannot seeโ]</li>
<li>(This suggests that) there is dark matter</li>
</ul>
</details>
</details>
<details style="margin-left: 20px;">
<summary class="subcategory">Falling asteroids</summary>
<details style="margin-left: 40px;">
<summary class="question"><strong>Explain</strong> why the mass of the asteroid would not remain constant as
the asteroid fell to the surface of the earth (2)</summary>
<p class="text" style="margin-left: 60px;">๐ Oct 2023</p>
<ul style="margin-left: 60px;">
<li>Work would be done on the asteroid by frictional forces Or Drag/friction causes heating (of the
asteroid)</li>
<li>Asteroid burns up</li>
</ul>
</details>
</details>
<details style="margin-left: 20px;">
<summary class="subcategory">Astronauts</summary>
<details style="margin-left: 40px;">
<summary class="question"><strong>Explain</strong> why astronauts may be described as โweightlessโ (2)
</summary>
<p class="text" style="margin-left: 60px;">๐ Jan 2024</p>
<ul style="margin-left: 60px;">
<li>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</li>
<li>They do not experience (normal) contact forces</li>
</ul>
</details>
</details>
<details style="margin-left: 20px;">
<summary class="subcategory">Gravitational fields</summary>
<details style="margin-left: 40px;">
<summary class="question"><strong>Explain</strong> why equipotential surfaces are not equally spaced (2)
</summary>
<p class="text" style="margin-left: 60px;">๐ Jun 2024</p>
<ul style="margin-left: 60px;">
<li>\(V_{\text{grav}} = -\frac{GM}{r}\), so gravitational potential \(\propto\frac{1}{r}\) Or
\(V_{\text{grav}} = -\frac{GM}{r}\) and \(G\) and \(M\) are constant</li>
<li>The equipotential surfaces become further apart with increasing distance (from Earth)</li>
</ul>
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<summary class="category"><strong>Miscellaneous</strong></summary>
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<summary class="subcategory">1.4 Materials</summary>
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<summary class="question"><strong>Explain</strong> how the airship is able to float in the air (2)</summary>
<p class="text" style="margin-left: 60px;">๐ Jun 2022</p>
<ul style="margin-left: 60px;">
<li>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)</li>
<li>Or (vertically) balanced forces act on the airship</li>
</ul>
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<summary class="subcategory">1.3 Mechanics</summary>
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<summary class="question">If the amplitude of oscillation is large enough, the man will lose contact with the
board at a point above the equilibrium position. <strong>Explain</strong> why. (3)</summary>
<p class="text" style="margin-left: 60px;">๐ Jun 2022</p>
<ul style="margin-left: 60px;">
<li>The resultant force on the man = \(mg โ R\) where \(R\) is the (normal) contact force from the board
</li>
<li>R decreases as his displacement (from the equilibrium position) increases</li>
<li>Man loses contact with board when \(R = 0\) Or Man loses contact with board when resultant force on man
is equal to his weight</li>
<li> OR</li>
<li>Acceleration (for SHM) increases as displacement increases</li>
<li>Maximum (downward) acceleration of man is \(g\)</li>
<li>Man loses contact with board when acceleration of the board is equal to \(g\)</li>
</ul>
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