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Secondary 2 Science Practice Paper 4
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TuitionGoWhere Practice Paper — Answer Key
Science Secondary 2 — Physical Sciences (Version 4 of 5)
Section A: Multiple Choice (10 marks)
1. D — Speed is a derived quantity (distance ÷ time). Mass, time, and length are base quantities. [1]
2. B — Average speed = total distance ÷ total time = 150 km ÷ 3 h = 50 km/h. [1]
3. C — A stretched spring stores elastic potential energy due to its deformation. [1]
4. C — GPE = mgh = 0.5 × 10 × 20 = 100 J. [1]
5. C — The principle of conservation of energy states that energy cannot be created or destroyed, only converted from one form to another. [1]
6. C — Work done = force × distance = 20 N × 5 m = 100 J. [1]
7. C — The SI unit of power is the watt (W). Joule is the unit of energy; newton is the unit of force; pascal is the unit of pressure. [1]
8. C — Useful energy output = efficiency × total input = 0.80 × 500 = 400 J. [1]
9. C — Coal is a fossil fuel and is non-renewable. Solar, wind, and hydroelectric energy are renewable sources. [1]
10. D — As the pendulum moves from the highest point (A) to the lowest point (B), gravitational potential energy decreases and is converted to kinetic energy. Total energy remains constant (conservation of energy). [1]
Section B: Structured Questions (20 marks)
11.
(a) Work done is the product of the force applied on an object and the distance moved by the object in the direction of the force. [1]
(b) Power is the rate of doing work, or the amount of work done per unit time. [1]
12.
(a) Weight = mass × gravitational field strength = mg = 200 × 10 = 2000 N [2]
Marking note: 1 mark for correct formula/substitution, 1 mark for correct answer with unit.
(b) Work done = force × distance = weight × height = 2000 × 15 = 30,000 J (or 30 kJ) [2]
Marking note: 1 mark for correct formula/substitution, 1 mark for correct answer with unit.
13.
(a) 2.5 kW = 2.5 × 1000 = 2500 W [1]
(b) Energy = power × time = 2500 × 30 = 75,000 J (or 75 kJ) [2]
Marking note: 1 mark for correct formula/substitution, 1 mark for correct answer with unit.
14.
(a) GPE at A = mgh = 400 × 10 × 25 = 100,000 J [2]
Marking note: 1 mark for correct substitution, 1 mark for correct answer with unit.
(b) The car starts from rest, so KE at A = 0 J. [1]
(c) By conservation of energy: Total energy at A = Total energy at B GPE at A + KE at A = GPE at B + KE at B 100,000 + 0 = (400 × 10 × 0) + KE at B KE at B = 100,000 J [2]
Marking note: 1 mark for stating conservation principle or correct substitution, 1 mark for correct answer.
(d) KE = ½mv² 100,000 = ½ × 400 × v² v² = 100,000 ÷ 200 = 500 v = √500 ≈ 22.4 m/s (accept 22.36 m/s or √500 m/s) [2]
Marking note: 1 mark for correct substitution into KE formula, 1 mark for correct answer with unit.
15.
(a) Work input = effort force × effort distance = 12 × 2.0 = 24 J [2]
(b) Work output = load × distance moved by load = 40 × 0.5 = 20 J [2]
(c) Efficiency = (work output ÷ work input) × 100% = (20 ÷ 24) × 100% = 83.3% (accept 83% or 250/3 %) [2]
Marking note: 1 mark for correct formula/substitution, 1 mark for correct answer. Common mistake: students may forget to multiply by 100% or may invert the ratio.
Section C: Application Question (10 marks)
16.
(a) Efficiency is the ratio of useful energy output to the total energy input, expressed as a percentage. It measures how well a system converts input energy into useful output energy. [2]
Marking note: 1 mark for defining efficiency as a ratio/comparison of output to input; 1 mark for mentioning percentage or "useful" energy.
(b) GPE lost per second = mgh (where m is mass per second) = 500 × 10 × 80 = 400,000 J/s (or 400 kJ/s) [2]
Marking note: 1 mark for correct substitution, 1 mark for correct answer with unit.
(c) Useful electrical power output = efficiency × input power = 0.70 × 400,000 = 280,000 W (or 280 kW) [2]
Marking note: 1 mark for correct formula/substitution, 1 mark for correct answer with unit.
(d) Any two of the following:
- Energy is lost as heat due to friction in the pipes and turbines.
- Energy is lost as sound energy.
- Energy is lost due to turbulence and resistance of water flow.
- Some energy is used to overcome mechanical resistance in the generator. [2]
Marking note: 1 mark each for any two valid reasons.
(e) Advantage (any one):
- Renewable / sustainable energy source (water cycle replenishes supply).
- No air pollution or greenhouse gas emissions during operation.
- Low running costs once built.
Disadvantage (any one):
- High initial construction cost.
- Can disrupt local ecosystems and displace communities.
- Dependent on rainfall and geographic location. [2]
Marking note: 1 mark for a valid advantage, 1 mark for a valid disadvantage.
End of Answer Key