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Secondary 1 Science Semestral Assessment 2 (End of Year) Paper 1
Free Sec 1 Science SA2 Paper 1, LongCat Exam version, with questions, answers, and syllabus-aligned practice for Singapore students.
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Questions
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Answers
Answer Key – SA2 Practice Paper Version 1 of 5
Secondary 1 Science – Physical Sciences
Section A – Multiple Choice (10 marks)
1. (c) 30 J
- Marking: 1 mark for correct answer.
- Common mistake: Students may divide 20 by 1.5 (option b) instead of multiplying.
2. (c) N/m²
- Marking: 1 mark for correct answer.
- Note: Pressure = Force / Area, so the unit is N/m² (also called pascal, Pa).
3. (c) kinetic energy
- Marking: 1 mark for correct answer.
- Reasoning: At the bottom of the slope, all gravitational potential energy has been converted to kinetic energy (assuming no friction).
4. (a) Chemical energy → Electrical energy → Light energy
- Marking: 1 mark for correct answer.
- Note: The battery stores chemical energy, which is converted to electrical energy, which then powers the bulb to produce light (and heat).
5. (b) 160 J
- Marking: 1 mark for correct answer.
- Working: Net force = 50 N − 10 N = 40 N; Work = 40 N × 4.0 m = 160 J.
- Common mistake: Students may use the applied force of 50 N (option c) instead of the net force.
6. (c) A sharp knife cuts better because it applies force over a smaller area.
- Marking: 1 mark for correct answer.
- Reasoning: Pressure = Force / Area. A smaller area means greater pressure for the same force.
7. (c) The total mechanical energy at A equals the total mechanical energy at B.
- Marking: 1 mark for correct answer.
- Reasoning: In the absence of air resistance, total mechanical energy (KE + GPE) is conserved throughout the swing.
8. (a) 0 J
- Marking: 1 mark for correct answer.
- Reasoning: Work = Force × distance moved in the direction of the force. Since the bag is stationary, the displacement is 0, so work done is 0 J.
9. (b) Pressure = Force ÷ Area
- Marking: 1 mark for correct answer.
10. (c) 400 J
- Marking: 1 mark for correct answer.
- Working: Useful energy output = 80% × 500 J = 0.80 × 500 = 400 J.
Section B – Structured Response (25 marks)
11. (4 marks)
(a) Work done = 60 J [2]
- Working: W = F × d = 20 N × 3.0 m = 60 J
- Marks: 1 mark for correct formula/substitution, 1 mark for correct answer with unit.
(b) Chemical energy (in the student's muscles) → Kinetic energy (of the trolley) [1]
- Marking: 1 mark for correct energy conversion stated.
- Accept: "Chemical energy to kinetic energy" or equivalent.
(c) Some of the work done is converted to thermal energy (heat) due to friction between the trolley and the floor. [1]
- Marking: 1 mark for stating that energy is lost as heat/thermal energy due to friction.
- Accept: "Some work is used to overcome friction" or "Some energy is converted to heat."
12. (5 marks)
(a) Points X and Y. The bob has maximum gravitational potential energy at X and Y because these are the highest points of the swing where the bob is momentarily at rest and at maximum height above the lowest point. [2]
- Marks: 1 mark for identifying X and Y, 1 mark for explaining that GPE is maximum at the highest point(s) / where height is greatest.
(b) The lowest point of the swing (the midpoint between X and Y). At this point, the bob is moving at its fastest speed, so kinetic energy is maximum. All the gravitational potential energy has been converted to kinetic energy. [2]
- Marks: 1 mark for identifying the lowest/midpoint, 1 mark for explaining maximum speed / all GPE converted to KE.
(c) The gravitational potential energy at X equals the gravitational potential energy at Y. This is because X and Y are at the same vertical height above the lowest point, and GPE depends on height (GPE = mgh). [1]
- Marking: 1 mark for stating they are equal with a valid reason (same height).
13. (4 marks)
(a) Weight = 20 N [1]
- Working: W = mg = 2.0 kg × 10 N/kg = 20 N
- Marking: 1 mark for correct answer with unit.
(b) Pressure = 2000 Pa (or 2000 N/m²) [3]
- Working:
- Smallest face area = 5 cm × 2 cm = 10 cm² = 10 × 10⁻⁴ m² = 1.0 × 10⁻³ m²
- Force = weight = 20 N
- Pressure = F / A = 20 N / (1.0 × 10⁻³ m²) = 20,000 Pa = 2.0 × 10⁴ Pa
- Correction: Let me recalculate. Smallest face = 5 cm × 2 cm = 10 cm² = 10 × 10⁻⁴ m² = 0.001 m². Pressure = 20 / 0.001 = 20,000 Pa.
- Marks: 1 mark for correct area conversion to m², 1 mark for correct substitution into P = F/A, 1 mark for correct answer with unit.
Revised answer for 13(b): Pressure = 20,000 Pa (or 2.0 × 10⁴ Pa)
14. (5 marks)
(a) Work done = 2400 J [2]
- Working: W = F × d = 200 N × 12 m = 2400 J
- Marks: 1 mark for correct formula/substitution, 1 mark for correct answer with unit.
(b) Power = 300 W [2]
- Working: P = W / t = 2400 J / 8 s = 300 W
- Marks: 1 mark for correct formula/substitution, 1 mark for correct answer with unit.
(c) One assumption: The load is lifted at constant speed (so the force applied equals the weight), OR air resistance is negligible, OR the crane applies a force equal to the weight of the load throughout. [1]
- Marking: 1 mark for any valid assumption.
15. (6 marks)
(a) Work input = 8.0 J [2]
- Working: Work input = Force along ramp × distance along ramp = 4.0 N × 2.0 m = 8.0 J
- Marks: 1 mark for correct substitution, 1 mark for correct answer with unit.
(b) Work output = 5.0 J [2]
- Working: Work output = Force to lift box × vertical height = 10 N × 0.5 m = 5.0 J
- Marks: 1 mark for correct substitution, 1 mark for correct answer with unit.
(c) Efficiency = 62.5% [2]
- Working: Efficiency = (Work output / Work input) × 100% = (5.0 / 8.0) × 100% = 62.5%
- Marks: 1 mark for correct substitution, 1 mark for correct answer with unit (%).
16. (5 marks)
(a) Gain in GPE = 2400 J [2]
- Working: GPE = mgh = 40 kg × 10 N/kg × 6.0 m = 2400 J
- Marks: 1 mark for correct substitution, 1 mark for correct answer with unit.
(b) Average power = 200 W [2]
- Working: Power = Work / time = 2400 J / 12 s = 200 W
- Marks: 1 mark for correct substitution, 1 mark for correct answer with unit.
(c) The boy also does work to overcome friction/air resistance, and some energy is converted to heat in his muscles (kinetic energy of moving limbs). The calculated power only accounts for the gain in GPE, not the total energy expended. [1]
- Marking: 1 mark for any valid reason (e.g., energy lost to heat, work against friction, additional kinetic energy).
Section C – Data Interpretation & Application (15 marks)
17. (5 marks)
(a) Bulb S (LED) – it has the highest efficiency at 25%. [1]
- Marking: 1 mark for correct answer.
(b) Useful light energy output = 30 J [2]
- Working:
- Total energy input = Power × time = 60 W × 10 s = 600 J
- Useful light energy = 5% × 600 J = 0.05 × 600 = 30 J
- Marks: 1 mark for calculating total energy input (600 J), 1 mark for correct answer with unit.
(c) Bulb S has a higher efficiency (25%) compared to bulb P (5%). This means bulb S converts a greater proportion of electrical energy into useful light energy and wastes less energy as heat. Therefore, to produce the same amount of useful light energy, bulb S requires less total electrical energy input than bulb P. [2]
- Marks: 1 mark for stating that bulb S has higher efficiency, 1 mark for explaining that less energy is wasted / less input energy is needed for the same output.
18. (6 marks)
(a) Independent variable: Height of drop (h). [1]
- Marking: 1 mark for correct answer.
(b) One constant variable (any one of): The same ball is used (same mass), the same type of sand is used, the sand is levelled flat before each drop, the ball is dropped (not thrown). [1]
- Marking: 1 mark for any valid controlled variable.
(c) As the height of drop increases, the depth of the crater increases. The relationship is positive/direct – when the height increases, the crater depth also increases, though not in direct proportion (the increase in depth becomes slightly smaller at higher heights). [2]
- Marks: 1 mark for stating that crater depth increases with height, 1 mark for describing the nature of the relationship (positive/direct, or noting it is not perfectly linear).
(d) When the ball is dropped from a greater height, it has more gravitational potential energy (GPE = mgh). As it falls, this GPE is converted to kinetic energy. At the greater height, the ball has more GPE, so it reaches a higher speed (more KE) just before hitting the sand. The ball with more kinetic energy does more work on the sand, pushing more sand aside and creating a deeper crater. [2]
- Marks: 1 mark for linking greater height to more GPE/KE, 1 mark for explaining that more KE means more work done on the sand, resulting in a deeper crater.
19. (4 marks)
(a) The pressure at the base of Container A is equal to the pressure at the base of Container B. This is because the pressure in a liquid depends on the depth (height) of the liquid and its density (P = ρgh), not on the base area or the total volume of liquid. Since both containers have the same water depth and the same liquid (water), the pressure at the base is the same. [2]
- Marks: 1 mark for stating the pressures are equal, 1 mark for correct explanation (pressure depends on depth/density, not base area).
(b) The force exerted by the water on the base of Container B is greater than that on Container A. Since pressure is the same at the base of both containers but Container B has a larger base area, the force is greater (F = P × A). Alternatively, Container B holds more water (greater volume and therefore greater weight), so the total force (weight of water) on the base is greater. [2]
- Marks: 1 mark for stating that the force on B is greater, 1 mark for correct explanation (larger area at same pressure, or greater weight of water).
20. (7 marks)
(a) Work input = 600 J [2]
- Working: Work input = Force applied × distance moved by rope = 150 N × 4.0 m = 600 J
- Marks: 1 mark for correct substitution, 1 mark for correct answer with unit.
(b) Work output = 400 J [2]
- Working: Work output = Weight of bricks × vertical height raised = 400 N × 1.0 m = 400 J
- Marks: 1 mark for correct substitution, 1 mark for correct answer with unit.
(c) Efficiency = 66.7% (or 66⅔%) [2]
- Working: Efficiency = (Work output / Work input) × 100% = (400 / 600) × 100% = 66.7%
- Marks: 1 mark for correct substitution, 1 mark for correct answer with unit (%).
(d) Some work is done to overcome friction in the pulley / some work is used to lift the weight of the pulley or rope / energy is lost as heat due to friction. [1]
- Marking: 1 mark for any valid reason why efficiency is less than 100%.
Total: 50 marks
Mark Distribution Summary:
| Section | Marks |
|---|---|
| A: Multiple Choice (Q1–10) | 10 |
| B: Structured Response (Q11–16) | 25 |
| C: Data Interpretation & Application (Q17–20) | 15 |
| Total | 50 |