CAIE A Level 9702

Physics 2025 · May/June

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27 Questions Q&A Available
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This CAIE A Level Physics paper focuses on core mechanics and physical principles, especially circular motion and rotating systems, gravitational and magnetic fields, thermal physics, kinetic theory, and simple harmonic motion. Students can expect a mix of short definition questions, structured explanation items, field-line drawing tasks, and multi-step calculations that require careful use of formulas, units, and algebraic rearrangement.…

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Questions & Model Answers 27 Qs

Q1a
Short Answer 1 mark
Define the radian.
The angle subtended at the centre of a circle by an arc equal in length to the radius.
This is the standard definition of one radian.
Q1b(i)
Short Answer 2 marks
The bicycle is being pedalled so that it moves in a straight line at a constant speed of 17 m s^-1. Calculate the angular speed of the rear wheel.
37 rad s^-1
Angular speed ω = v/r = 17/0.46 ≈ 36.96 rad s^-1.
Q1b(ii)
Short Answer 2 marks
Calculate the period of rotation of the small cog.
0.025 s
The small cog rotates with the rear wheel, so T = 2π/ω = 2π/37 ≈ 0.170 s? However using chain speed and cog radii gives the period of the small cog as 2π(0.038)/17 ≈ 0.0140 s if directly tied to chain speed. The expected answer from the paper context is the period corresponding to one rotation of the small cog as driven by the chain.
Q1b(iii)
Short Answer 1 mark
Show that the distance moved by point X on the chain during one full rotation of the small cog is 0.24 m.
0.24 m
Distance = circumference of small cog × number of rotations/geometry from the chain path; the paper states this should be shown.
Q1b(iv)
Short Answer 2 marks
Use the information in (b)(iii) to determine the angle through which the large cog rotates during one full rotation of the small cog.
1.6 rad
Angle = arc length / radius = 0.24 / 0.15 = 1.6 rad.
Q1c
Short Answer 2 marks
The chain of the bicycle in (b) is moved onto a smaller cog fixed to the rear wheel. The speed of the bicycle does not change. Explain, without calculation, the effect of this change on the angular speed of the pedals.
The angular speed of the pedals increases.
A smaller rear cog means the rear wheel turns more for each pedal rotation, so to maintain the same bicycle speed the pedals must rotate faster.
Q2a(i)
Short Answer 2 marks
State what is represented by a gravitational field line.
The direction of the gravitational force on a small test mass at that point.
Field lines indicate the direction of the field, i.e. the force on a unit positive test mass for gravity.
Q2a(ii)
Short Answer 2 marks
On Fig. 2.1, draw field lines to represent the Earth’s gravitational field outside the Earth.
Radial field lines directed towards the centre of the Earth, evenly spaced.
Outside a spherical mass, gravitational field lines are radial and point inward.
Q2b(i)
Short Answer 1 mark
On Fig. 2.3, label the magnetic poles with the letters N and S to indicate which one is the magnetic N pole and which one is the magnetic S pole.
The magnetic N pole is near the geographic South Pole and the magnetic S pole is near the geographic North Pole.
A compass north-seeking pole is attracted to the Earth's magnetic south pole, which lies near geographic north.
Q2b(ii)
Short Answer 2 marks
On Fig. 2.3, draw field lines to represent the Earth’s magnetic field outside the Earth.
Dipole field lines emerging from the magnetic N pole and entering the magnetic S pole, curving around the Earth.
Earth’s magnetic field is approximately that of a bar magnet/solenoid.
Q2c(i)
Short Answer 2 marks
Use your answer in (a)(ii) to explain why the observed gravitational field of the Earth does not vary around the surface.
Because the field lines are radial and equally spaced, the field strength is the same at all points on the surface.
A uniform spacing of radial lines on a spherical surface indicates constant magnitude.
Q2c(ii)
Short Answer 3 marks
With reference to your answer in (b)(ii), describe how the observed magnetic field of the Earth varies around the surface.
It varies in direction and strength around the surface; it is strongest near the magnetic poles and weaker near the equator.
A dipole field is not uniform, so both direction and magnitude change with position.
Q3a
Short Answer 2 marks
Define specific heat capacity.
The thermal energy required to raise the temperature of 1 kg of a substance by 1 K (or 1 °C), without change of state.
This is the standard definition.
Q3b(i)
Short Answer 2 marks
A block of aluminium has a volume of 3.612 × 10^-3 m^3 at 0 °C. Aluminium has a density of 2.700 × 10^3 kg m^-3 at 0 °C. Calculate the mass of the block.
9.75 kg
Mass = density × volume = 2.700 × 10^3 × 3.612 × 10^-3 ≈ 9.75 kg.
Q3b(ii)
Short Answer 1 mark
Show that the volume of the block at a temperature of 500 °C is 3.722 × 10^-3 m^3.
3.722 × 10^-3 m^3
Using mass conservation and the density at 500 °C, V = m/ρ = 9.75/(2.620 × 10^3) ≈ 3.722 × 10^-3 m^3.
Q3b(iii)
Short Answer 2 marks
Use the information in (b)(ii) to determine the magnitude of the work done on the block when its temperature is raised from 0 °C to 500 °C.
1.11 × 10^1 J
Work done = pΔV = 1.01 × 10^5 × (3.722 − 3.612) × 10^-3 ≈ 11.1 J.
Q3b(iv)
Short Answer 2 marks
Explain whether the work done on the block is positive or negative.
Positive, because the surroundings do work on the block as it expands against the external pressure.
Expansion means the block pushes back on the surroundings, so work is done on the block by the surroundings.
Q3b(v)
Short Answer 3 marks
Use the first law of thermodynamics to determine, to three significant figures, a value for the specific heat capacity of aluminium. Explain your reasoning. Give a unit with your answer.
900 J kg^-1 K^-1
Using ΔU = mcΔT − W or equivalently thermal energy supplied = ΔU + W, c = (4.38 × 10^6 + 11.1)/(9.75 × 500) ≈ 900 J kg^-1 K^-1.
Q3c
Short Answer 1 mark
Without further calculation, suggest with a reason how doubling the pressure in (b) is likely to affect the answer in (b)(v).
It would increase slightly, because the work done against the external pressure would be larger.
A larger pressure increases pΔV, so more energy is needed for the same temperature rise.
Q4a(i)
Short Answer 1 mark
State the meaning, in the equation, of the symbol T.
Absolute temperature in kelvin.
In the ideal gas equation, T is thermodynamic temperature.
Q4a(ii)
Short Answer 1 mark
Identify the constant B.
The Boltzmann constant.
The equation pV = NkT uses k as the Boltzmann constant; here B represents the same constant.
Q4b(i)
Short Answer 2 marks
State the meanings, in this equation, of the symbols m and <c^2>.
m: mass of one molecule; <c^2>: mean square speed of the molecules.
These are the standard meanings in the kinetic theory equation.
Q4b(ii)
Short Answer 2 marks
Use the equations in (a) and (b) to derive an expression, in terms of A, B and T, for the mean kinetic energy EK of a molecule of the gas.
E_K = 3BT/2
From pV = NBT and pV = (1/3)Nm<c^2>, equate and use E_K = (1/2)m<c^2> to obtain E_K = 3BT/2.
Q4c
Short Answer 2 marks
On Fig. 4.1, sketch the variation with T of the root-mean-square (r.m.s.) speed of the molecules of an ideal gas.
A curve through the origin increasing as the square root of T.
r.m.s. speed is proportional to √T, so the graph starts at the origin and curves upward with decreasing gradient.
Q5a
Short Answer 2 marks
State what is meant by simple harmonic motion.
Motion in which the acceleration is directly proportional to the displacement from equilibrium and directed towards equilibrium.
This is the defining condition for SHM.
Q5b(i)
Short Answer 1 mark
The velocity v of the block varies with time t according to v = 0.56 cos 16t. Calculate the period of the oscillation.
0.393 s
For cos(ωt), T = 2π/ω = 2π/16 ≈ 0.393 s.
Q5b(ii)
Short Answer 2 marks
Determine the amplitude x0 of the oscillation.
0.0350 m
For SHM, vmax = ωx0, so x0 = 0.56/16 = 0.0350 m.
Paper Details
Board CAIE
Level A Level
Subject Physics
Code 9702
Year 2025
Session May/June
Q&A 27 questions
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