HKDSE Physics Paper 1 Section A (MCQ) Practice Paper | 36 questions, 36 marks, 60 minutes

2026-10-30

HKDSE Physics Paper 1

HKDSE Physics Paper 1 Section A MCQ practice: 36 questions, 36 marks, 60 minutes on mechanics, waves, electricity, heat and the atomic world, with answers and worked steps. Paper 1 is 50% of the subject; Section A only, original items.

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Paper details　Level: S6 (HKDSE) | Subject: Physics | Time: 60 minutes | Marks: 36 | Questions: 36

Part A: Mechanics and motion (kinematics, force and motion, work and energy)

Choose the best answer. Each question carries 1 mark.

#	Question	Answer and marking notes
1	A car accelerates uniformly from rest at 2.0 m s⁻² for 3.0 s. Its displacement is: A. 6.0 m B. 9.0 m C. 12.0 m D. 18.0 m	B — s = ut + ½at² = 0 + ½ × 2.0 × 3.0² = 9.0 m.
2	A ball moving at 5.0 m s⁻¹ accelerates at 2.0 m s⁻² in the same direction. Its speed after 4.0 s is: A. 9.0 m s⁻¹ B. 11.0 m s⁻¹ C. 13.0 m s⁻¹ D. 26.0 m s⁻¹	C — v = u + at = 5.0 + 2.0 × 4.0 = 13.0 m s⁻¹.
3	A net force of 30 N acts on a 5.0 kg object. Its acceleration is: A. 2.0 m s⁻² B. 5.0 m s⁻² C. 6.0 m s⁻² D. 150 m s⁻²	C — a = F/m = 30/5.0 = 6.0 m s⁻².
4	A 45 kg instrument rests on the Moon where g = 1.62 N kg⁻¹. Its weight is: A. 45 N B. 72.9 N C. 162 N D. 441 N	B — W = mg = 45 × 1.62 = 72.9 N; mass is unchanged, weight depends on g.
5	A 0.50 kg ball hits a wall at 8.0 m s⁻¹ and rebounds at 6.0 m s⁻¹. The magnitude of its momentum change is: A. 1.0 N s B. 4.0 N s C. 7.0 N s D. 14 N s	C — Opposite directions: Δp = m(v − u) = 0.50 × (6.0 + 8.0) = 7.0 N s.
6	If the impact in the previous question lasts 0.050 s, the average force on the ball is: A. 20 N B. 70 N C. 140 N D. 280 N	C — F = Δp/t = 7.0/0.050 = 140 N.
7	A 50 N force at 60° above the horizontal pulls a box 10 m along the floor. Work done by the force is: A. 0 J B. 250 J C. 433 J D. 500 J	B — W = Fd cosθ = 50 × 10 × cos 60° = 50 × 10 × 0.5 = 250 J.
8	A crane lifts a 20 kg load 5.0 m at constant speed in 4.0 s (g = 10 N kg⁻¹). Average power is: A. 100 W B. 250 W C. 400 W D. 4000 W	B — P = mgh/t = 20 × 10 × 5.0/4.0 = 250 W.
9	A 1 200 kg car travels at 15 m s⁻¹. Its kinetic energy is: A. 1.35 × 10⁴ J B. 1.35 × 10⁵ J C. 2.70 × 10⁵ J D. 1.35 × 10⁶ J	B — KE = ½mv² = ½ × 1 200 × 15² = 135000 J = 1.35 × 10⁵ J.
10	A spring stretches 3.0 cm under a 15 N pull. Its spring constant is: A. 5.0 N m⁻¹ B. 45 N m⁻¹ C. 500 N m⁻¹ D. 1 500 N m⁻¹	C — k = F/x = 15/0.030 = 500 N m⁻¹ (x must be in metres).
11	A stone falls freely from 45 m (g = 10 m s⁻²). The time to reach the ground is: A. 2.0 s B. 3.0 s C. 4.5 s D. 9.0 s	B — s = ½gt² → t = √(2 × 45/10) = 3.0 s.
12	An 8.0 kg block slides on a horizontal floor with μ = 0.25 (g = 10 N kg⁻¹). Friction and deceleration are: A. 10 N, 1.25 m s⁻² B. 20 N, 2.5 m s⁻² C. 80 N, 10 m s⁻² D. 20 N, 5.0 m s⁻²	B — f = μmg = 0.25 × 8.0 × 10 = 20 N; a = f/m = 2.5 m s⁻².

Part B: Waves, electricity and magnetism (waves, light, circuits, electromagnetism)

Choose the best answer. Each question carries 1 mark.

#	Question	Answer and marking notes
13	A wave of frequency 50 Hz has wavelength 0.68 m. Its speed is: A. 0.014 m s⁻¹ B. 17 m s⁻¹ C. 34 m s⁻¹ D. 68 m s⁻¹	C — v = fλ = 50 × 0.68 = 34 m s⁻¹.
14	A pendulum completes 240 oscillations in 60 s. Its period and frequency are: A. 4.0 s, 0.25 Hz B. 0.25 s, 4.0 Hz C. 0.25 s, 2.0 Hz D. 60 s, 240 Hz	B — T = 60/240 = 0.25 s; f = 1/T = 4.0 Hz.
15	Light enters glass (n = 1.5) from air at 30°. The angle of refraction is about: A. 15.0° B. 19.5° C. 30.0° D. 48.6°	B — sin r = sin 30°/1.5 = 0.333, so r ≈ 19.5°.
16	A medium has refractive index 1.5. The critical angle for light going to air is about: A. 30.0° B. 41.8° C. 48.6° D. 60.0°	B — sin c = 1/n = 0.667, so c ≈ 41.8°.
17	An object is 15 cm from a convex lens of focal length 10 cm. The image distance is: A. 6.0 cm B. 15 cm C. 30.0 cm D. 30 cm	C — 1/v = 1/f − 1/u = 1/10 − 1/15 → v = 30.0 cm; real, inverted, magnified 2×.
18	A shout returns as an echo after 0.80 s (speed of sound 340 m s⁻¹). The cliff is: A. 136 m B. 272 m C. 544 m D. 340 m	A — Sound travels there and back: d = vt/2 = 340 × 0.80/2 = 136 m.
19	A current of 2.5 A flows for 4.0 minutes. The charge passed is: A. 10 C B. 150 C C. 600 C D. 960 C	C — Q = It = 2.5 × (4.0 × 60) = 600 C.
20	6 Ω and 4 Ω resistors in series are connected to a 20 V supply. The current is: A. 0.5 A B. 2.0 A C. 4.0 A D. 5.0 A	B — R = 6 + 4 = 10 Ω, I = V/R = 20/10 = 2.0 A.
21	Two resistors, 6 Ω and 3 Ω, are connected in parallel. The equivalent resistance is: A. 1.5 Ω B. 2.0 Ω C. 4.5 Ω D. 9.0 Ω	B — 1/R = 1/6 + 1/3 = 1/2 → R = 2.0 Ω, always smaller than the smallest resistor.
22	A 4.0 Ω resistor is connected across 12 V. The power dissipated is: A. 3.0 W B. 12 W C. 36 W D. 144 W	C — P = V²/R = 12²/4.0 = 36 W.
23	A 2 000 W appliance runs for 3 hours at $1.2 per kWh. The cost is: A. $2.40 B. $4.80 C. $7.20 D. $72.00	C — Energy = 2.0 kW × 3 h = 6 kWh; cost = 6 × 1.2 = $7.20.
24	A transformer steps 220 V down to 11 V with 50 turns on the secondary. The primary turns are: A. 25 B. 100 C. 1000 D. 1100	C — Ns/Np = Vs/Vp → Np = 50 × 220/11 = 1000 turns.

Part C: Heat, atomic world and energy (heat, gases, radioactivity and energy)

Choose the best answer. Each question carries 1 mark.

#	Question	Answer and marking notes
25	0.50 kg of water is heated through 40 °C (c = 4 200 J kg⁻¹ K⁻¹). Heat absorbed is: A. 10 500 J B. 84000 J C. 168 000 J D. 336 000 J	B — E = mcΔT = 0.50 × 4 200 × 40 = 84000 J.
26	0.20 kg of water at 100 °C is completely vaporised (L = 2.26 × 10⁶ J kg⁻¹). Energy needed: A. 4.52 × 10⁴ J B. 4.52 × 10⁵ J C. 2.26 × 10⁶ J D. 4.52 × 10⁶ J	B — E = mL = 0.20 × 2.26 × 10⁶ = 452000 J = 4.52 × 10⁵ J; temperature stays at 100 °C.
27	A 500 W heater warms 0.40 kg of water for 200 s with no heat loss (c = 4 200). The rise in temperature is: A. 29.8 °C B. 59.5 °C C. 119 K D. 150 °C	B — E = Pt = 500 × 200 = 100 000 J; ΔT = E/(mc) = 100 000/(0.40 × 4 200) = 59.5 °C.
28	A machine takes in 500 J and delivers 175 J of useful output. Its efficiency is: A. 17.5% B. 28.6% C. 35% D. 65%	C — Efficiency = useful output/input × 100% = 175/500 × 100% = 35%.
29	A source of half-life 5 days starts with 80 g. After 15 days the mass left is: A. 2.5 g B. 5.3 g C. 10.0 g D. 20 g	C — 15/5 = 3 half-lives, so 80/2³ = 10.0 g.
30	A fixed-volume gas is at 100 kPa and 300 K. Heated to 450 K, its new pressure is: A. 66.7 kPa B. 150.0 kPa C. 133 kPa D. 300 kPa	B — P1/T1 = P2/T2 → P2 = 100 × 450/300 = 150.0 kPa (temperature in K).
31	The liquid pressure at a depth of 0.60 m in water (ρ = 1 000 kg m⁻³, g = 10 N kg⁻¹) is: A. 600 Pa B. 6000 Pa C. 6 000 Pa D. 60 000 Pa	B — p = ρgh = 1 000 × 10 × 0.60 = 6000 Pa.
32	A metal block has mass 240 g and volume 30 cm³. Its density is: A. 0.125 g cm⁻³ B. 8.0 g cm⁻³ C. 2 400 g cm⁻³ D. 7 200 g cm⁻³	B — ρ = m/V = 240/30 = 8.0 g cm⁻³.
33	After emitting an α particle, a nucleus changes as follows: A. mass number −2, proton number −4 B. mass number −4, proton number −2 C. mass number −1, proton number −1 D. neither changes	B — An α particle is a helium nucleus (2p + 2n), so mass number −4 and proton number −2.
34	A 0.20 m wire carries 3.0 A in a 0.50 T field perpendicular to it. The force is: A. 0.03 N B. 0.30 N C. 3.0 N D. 30 N	B — F = BIL = 0.50 × 3.0 × 0.20 = 0.30 N.
35	A 1.5 kW solar panel runs for 4 hours in full sun. Energy generated: A. 0.375 kWh B. 6.0 kWh C. 6.0 kW D. 60 kWh	B — E = Pt = 1.5 kW × 4 h = 6.0 kWh.
36	A source counts 640 Bq now. After 3 half-lives the count rate is about: A. 213 Bq B. 80 Bq C. 160 Bq D. 40 Bq	B — Halves each half-life: 640 → 320 → 160 → 80 Bq.

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