Questions 1
(a) Topic – 8.c
(b) Topic-8.c
This question is about nuclear reactions.
(a) Nuclear fusion and nuclear fission release energy from the nuclear stores of atoms. The table gives some statements about nuclear fusion and some statements about nuclear fission. Place ticks (✓) in the table to show whether each statement applies to nuclear fusion or nuclear fission.
(b) In nuclear fusion, two positively charged nuclei must overcome the effects of the repulsive electrostatic force between them. Explain the two conditions needed to overcome the effects of this repulsive force and achieve nuclear fusion.
▶️Answer/Explanation
Ans
(a) all five rows correct = 3 marks
3-4 rows correct = 2 marks
1-2 rows correct = 1 mark
(b) high temperature;
(so that) nuclei will have high(er) speed or high(er) {kinetic energy/KE};
high pressure;
plus one from:
• (so that nuclei will be) closer together / eq;
• (so that nuclei are) more likely to collide/ eq;
Questions 2
(a) Topic – 1.c
(b) Topic-1.c
This question is about moments. Diagram 1 shows the raised lower leg of a person.
(a) (i) The moment of the weight of the lower leg about the pivot is 19Nm. A vertical force, F, is applied to the person’s foot to keep the lower leg raised. The lower leg does not move. Calculate the magnitude of force F, using the formula
moment = force × perpendicular distance from pivot
(ii) Which distance is used to calculate the moment of the weight of the lower leg about the pivot?
A 0.25m
B 0.28m
C 0.30m
D 0.55m
(b) Diagram 2 shows the person resting their lower leg on two supports.
(i) The centre of gravity of the lower leg is 0.25m away from support A and 0.35m away from support B. Explain whether force X or force Y is larger. Ignore the weight of the upper leg.
(ii) A bag of ice is placed on the lower leg, vertically above the centre of gravity. This causes force X and force Y to increase. The bag is then moved towards the person’s foot. Describe how force X and force Y change as the bag is moved towards the person’s foot.
▶️Answer/Explanation
Ans
(a) (i) substitution OR rearrangement;
evaluation;
e.g.
19 = force × 0.55 OR force = moment/distance
(force =) 35 (N)
(ii) A (0.25 m);
B is incorrect because this is not a perpendicular distance
C is incorrect because this is the distance between weight and force F
D is incorrect because this is the distance to force F
(b) (i) force X has the shorter distance to the CoG;
moments of two forces must be equal/eq;
so force X must be larger;
(ii) any three from:
force X decreases;
force Y increases;
change by the same amount;
total force remains the same;
Questions 3
(a) Topic – 4.c
(b) Topic-4.c
The diagram shows some apparatus that can be used to determine the specific heat capacity of water.
(a) Describe how a student could use this apparatus to determine the specific heat capacity of water. Include details of any additional equipment needed in your answer.
(b) (i) The table shows the student’s results.
Use the student’s results to calculate the specific heat capacity of water.
(ii) Give two reasons why the energy from the heater is not all retained in the thermal store of the water.
▶️Answer/Explanation
Ans
(a) any five from:
MP1. idea of mass of water = [mass of water and cup] − [mass of cup];
MP2. mass found on balance;
MP3. time measured on timer/stopwatch/stopclock;
MP4. idea of finding temperature change;
MP5. energy supplied = voltmeter reading × ammeter reading × time;
MP6. whole experiment repeated and averaged;
MP7. water stirred (throughout);
MP8. keep taking temperature after heater switched off for max temp;
MP9. plot a graph of temperature against time;
MP10. find gradient of temperature-time graph;
and one from:
MP11. use of equation “gradient = power of heater / m × c” or re-arrangement;
MP12. rearrangement of formula sheet equation;
i.e. c = energy supplied/(m × temp change)
(b) (i) substitution into given formula;
rearrangement;
evaluation;
e.g.
54 000 = 0.56 × c × 22
c = 54 000 / 0.56 × 22
(c =) 4400 (J/kg °C)
(ii) any two from:
MP1. heating of beaker/heating of thermometer;
MP2. heating of surroundings/heating of insulation;
MP3. insulation not perfect;
MP4. hole(s) in lid for thermometer/heater leave gaps;
Questions 4
(a) Topic – 7.d
(b) Topic-7.d
(c)Topic-7.d
The diagram shows a step-down transformer.
(a) The input power to the transformer is 16W. The transformer is used for 2.5 hours. Calculate the energy transferred to the transformer during this time.
(b) Explain how a transformer works. In your answer, include reasons for using
• two coils
• the iron core
• an a.c. power supply
(c) State how the primary coil of the transformer can be changed to increase the output voltage.
▶️Answer/Explanation
Ans
(a) substitution into given formula;
rearrangement;
evaluation;
e.g.
16 = energy / 2.5 (× 3600)
energy = 16 × 2.5 (× 3600)
(energy =) 140 000 (J)
(b) any six from:
MP1. it steps up or steps down the voltage;
MP2. current in (primary) coil produces magnetic field;
MP3. current is changing/alternating;
MP4. causing a (changing) magnetic field in the core;
MP5. the core strengthens the magnetic field;
MP6. idea that iron is a soft magnetic material I.e. can gain and lose its magnetism easily
MP7. field lines interact with (secondary) coil;
MP8. which induces a voltage in the secondary coil;
MP9. transformer won’t work with (steady) d.c.;
(c) less turns (on the primary coil) / eq;
Questions 5
(a) Topic – 4.c
(b) Topic-6.d
A sample of steam (water in a gas state) is cooled using a very cold freezer.
(a) The steam is cooled from an initial temperature of 150°C. Calculate the initial temperature of the steam in kelvin (K).
(b) The temperature-time graph shows how the temperature of the steam changes during the cooling process. The steam eventually becomes ice (water in a solid state).
(i) The graph shows five stages, A, B, C, D and E, of the cooling process. State which stages of the cooling process show a change of state.
(ii) Describe the differences in the arrangement of particles when the sample is in a gas state (steam) and a solid state (ice). You may draw a diagram to help your answer.
(iii) Explain whether or not the energy in the kinetic store of the particles changes when the sample is changing state.
▶️Answer/Explanation
Ans
(a) 423 (K);
(b) (i) B and D only;
(ii) particles closer together in solid;
particles have fixed or regular arrangement in solid but irregular in gas;
(iii) kinetic energy stays constant / eq;
and any two from:
• temperature stays constant (during state change);
• (average) speed of particles does not change;
• (kelvin) temperature is (directly) proportional to (average) kinetic energy of particles;
Questions 6
(a) Topic – 1.c
(b) Topic – 1.b
(c) Topic – 1.b
This question is about momentum and forces.
(a) State the principle of conservation of momentum.
(b) The diagram shows an air track that can be used to investigate motion without friction. Air comes out through a series of small holes in the air track. The air lifts the glider slightly above the track. A small spacecraft engine floats at rest on a cushion of air.
(i) State the momentum of the spacecraft engine when it is at rest.
(ii) The spacecraft engine ejects large numbers of xenon ions to the left. A mass of \(2.6 × 10^{−8} kg\) of xenon ions leaves the engine with a mean speed of 26km/s. Calculate the momentum of all the ejected xenon ions.
(iii) State the magnitude and direction of the spacecraft engine’s momentum after these xenon ions leave the engine.
(iv) The ions exert a force of 2.6mN on the spacecraft engine. The spacecraft engine has a mass of 1.2kg. Calculate the acceleration of the engine. Give your answer to 2 significant figures.
(c) The engine is designed to accelerate a spacecraft while the spacecraft is travelling through space. The spacecraft carries a mass of 0.75kg of xenon ions for the engine. When the engine is used, \(9.9 × 10^{−8} kg\) of xenon ions leave the engine each second. A student suggests that this small spacecraft engine would not be useful because the acceleration it produces is very small. Evaluate the student’s suggestion.
▶️Answer/Explanation
Ans
(a) idea that (total) momentum before = (total) momentum after (event);
(b) (i) zero/0/nought/nothing;
(ii) recall of momentum = mass × velocity;
substitution;
evaluation;
e.g.
p = mv
\(p = 2.6 × 10^{−8} × 26 000\)
\(p = 6.8 × 10^{−4}\)
(kg m/s)
(iii) \(6.8 × 10^{−4}\) (kg m/s);
right;
(iv) substitution into ‘F=ma’;
rearrangement;
evaluation;
answer given to 2s.f.;
e.g.
2.6 (×10⁻³) = 1.2 × acceleration
acceleration 2.6 (×10⁻³) / 1.2
(acceleration =) 2.16… × 10⁻³ (m/s²)
(acceleration =) 2.2 × 10⁻³ (m/s²)
(c) any two from:
MP1. idea of tiny amount of fuel ‘consumed’ per second;
MP2. any attempt of calculation of time to run out of xenon seen;
MP3. correct calculation of \(7.575… × 10^6 s\);
MP4. idea that ‘burn’ is for a long time;
MP5. idea that low acceleration for long time gives high speed change;
MP6. mass of spacecraft will be larger so acceleration is even smaller;
Questions 7
(a) Topic – 5.d
(b) Topic – 5.b
(c) Topic – 5.b
The diagram shows the screen of an oscilloscope when a sound wave is detected, and the oscilloscope settings.
(a) Give the name of the piece of equipment that is connected to the oscilloscope to detect the sound wave.
(b) (i) Use the trace on the oscilloscope to determine the time period of the detected sound wave.
(ii) Calculate the frequency of the detected sound wave.
(c) (i) State the formula linking energy transferred, charge and voltage.
(ii) The effective voltage of the oscilloscope trace can be calculated using the formula
\(effective \ voltage=\frac{amplitude \ of \ trace \ in \ V}{\sqrt 2}\)
Use the effective voltage to calculate the energy transferred when \(6.3 × 10^{−5}C\) of charge passes through the oscilloscope.
▶️Answer/Explanation
Ans
(a) microphone;
(b) (i) determination of number of squares for one period;
use of timebase to determine appropriate period in seconds;
e.g.
period = 8/1.5 = 5.3 squares
period = (5.3 × 0.002 =) 0.011(s)
(ii) use of f = 1 / T to evaluate frequency;
e.g.
frequency = (1 / 0.011 =) 91 (Hz)
(c) (i) energy (transferred) = charge × voltage;
(ii) amplitude of signal in volts determined;
evaluation of effective voltage;
evaluation of energy transferred;
e.g.
amplitude = 2 squares × 5 = 10 V
effective voltage = 10 / √2 = 7.1 V
energy transferred = (7.1 × 6.3 × 10⁻⁵ 4.5 × 10⁻⁴ (J)
Questions 8
(a) Topic – 9.b
(b) Topic-9.d
This question is about red-shift.
(a) The diagram shows two identical stars, A and B, orbiting each other.
Light from each star arrives at Earth. As the stars move in their orbit, the wavelength of the light observed at Earth changes due to the Doppler effect. Add an X to the diagram to show the position of star B when the light emitted from it shows maximum red-shift when detected on Earth.
(b) Light is received on Earth from a distant galaxy. The longest wavelength of light arriving at Earth from the galaxy is 561nm. A lamp on Earth produces the same light with a wavelength of 550nm. Calculate the velocity of the galaxy.
[speed of light = \(3.0 × 10^8 m/s\)]
▶️Answer/Explanation
Ans
(a) X at 3 o’clock position on orbit by eye;
(b) difference in wavelength: 11 (nm);
all substitutions correct in formula;
rearrangement;
evaluation;
e.g.
∆λ = 561 − 550 = 11 (nm)
\(11/550 = v / 3.0 × 10^8\)
\(v = 11/550 × 3.0 × 10^8\)
\((v =) 6.0 × 10^6 (m/s)\)