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Secondary 2 Science Physical Sciences Quiz
Free Sec 2 Science Physical Sciences quiz, LongCat Exam version, with questions, answers, and syllabus-aligned practice for Singapore students.
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Secondary 2 Science Quiz - Physical Sciences
Answer Key
Section A: Multiple Choice
1. B [1]
Explanation: As the ball rolls down the slope, it loses height (decreasing gravitational potential energy) and gains speed (increasing kinetic energy). Total mechanical energy is conserved in the absence of friction.
2. A [1]
Working: Work done against friction = Frictional force × distance = 8 N × 5 m = 40 J
Common mistake: Students may calculate the work done by the applied force (20 N × 5 m = 100 J) instead of the work done against friction.
3. C [1]
Explanation: Power is measured in watts (W). Joule is the unit of energy, Newton is the unit of force, and Pascal is the unit of pressure.
4. C [1]
Working: GPE = mgh = 2 kg × 10 N/kg × 3 m = 60 J
5. B [1]
Working: P = E / t = 600 J / 30 s = 20 W
Section B: Short Answer
6. [2]
The principle of conservation of energy states that energy cannot be created or destroyed. [1] It can only be converted from one form to another, and the total energy in a closed system remains constant. [1]
Marking note: Award 1 mark for "cannot be created or destroyed" and 1 mark for mentioning conversion or constancy of total energy. Answers stating only one component receive 1 mark only.
7. [2]
Work done is defined as the product of the force applied on an object and the distance moved by the object in the direction of the force. [1] Work done = Force × Distance (in the direction of the force). [1]
Marking note: Both the definition and the formula (or equivalent statement) are required for full marks.
8. [2]
Work done = Force × Distance = mg × h [1]
= 50 kg × 10 N/kg × 4 m = 2000 J [1]
9. [2]
(i) Kinetic energy [1]
(ii) Chemical energy (stored in the fuel) / Thermal energy / Sound energy [1]
Marking note: Accept any two valid forms. "Kinetic" and "chemical" are the most common expected answers.
10. [2]
The pendulum eventually comes to rest because some of its mechanical energy is converted to thermal energy (heat) due to air resistance and friction at the pivot. [1] The total energy is conserved — it is not destroyed but is transferred to the surroundings as thermal energy, which is not useful for the pendulum's motion. [1]
Marking note: Students must acknowledge that energy is converted/transferred, not destroyed, to receive full marks.
Section C: Structured Response
11.
(a) [2]
GPE at A = mgh = 400 kg × 10 N/kg × 25 m [1]
= 100,000 J (or 100 kJ) [1]
(b) [2]
Kinetic energy at B = 100,000 J [1]
By the principle of conservation of energy, the gravitational potential energy at A is entirely converted to kinetic energy at B (since there is no friction or air resistance, and point B is at ground level where GPE = 0). [1]
(c) [2]
KE at B = ½mv²
100,000 = ½ × 400 × v² [1]
v² = 100,000 / 200 = 500
v = √500 = 22.4 m/s (or 22 m/s to 2 s.f.) [1]
Marking note: Accept 22.36 m/s or 22.4 m/s. Award 1 mark for correct substitution even if final answer is wrong.
12.
(a) [2]
P = IV
1500 = I × 240 [1]
I = 1500 / 240 = 6.25 A [1]
(b) [2]
Energy = Power × Time
= 1500 W × (5 × 60) s = 1500 × 300 = 450,000 J [1]
OR in kWh:
= 1.5 kW × (5/60) h = 1.5 × 0.0833 = 0.125 kWh [1]
Marking note: Accept either 450,000 J or 0.125 kWh. If the student gives the answer in joules, award full marks. If in kWh, also award full marks.
13.
(a) [1]
Work done = Force × Distance = 800 N × 15 m = 12,000 J
(b) [2]
Power = Work / Time = 12,000 / 6 [1]
= 2,000 W (or 2 kW) [1]
(c) [1]
Some energy is lost as heat due to friction in the moving parts of the crane / Some energy is used to lift the cable itself / Energy is lost as sound. [1]
Marking note: Accept any one valid reason.
14.
(a) [2]
GPE gained = mgh = 45 × 10 × 6 [1]
= 2,700 J [1]
(b) [2]
Minimum power = Work / Time = 2,700 / 8 [1]
= 337.5 W [1]
(c) [1]
The boy also does work to overcome friction between his shoes and the stairs / The boy also gains kinetic energy (he is moving, not just gaining height) / Energy is lost as heat from his body. [1]
Marking note: Accept any one valid reason.
15.
(a) [2]
KE = ½mv² = ½ × 0.5 × 20² [1]
= ½ × 0.5 × 400 = 100 J [1]
(b) [2]
At maximum height, all KE is converted to GPE.
mgh = 100
0.5 × 10 × h = 100 [1]
5h = 100
h = 20 m [1]
Marking note: Award 1 mark for equating KE to GPE, and 1 mark for the correct final answer.
Section D: Data Interpretation
16. [1]
Weight = mg = 10 × 10 = 100 N
17. [2]
Useful work output = Weight × Height raised [1]
= 100 N × 2 m = 200 J [1]
18. [2]
Total work input = Effort force × Distance moved by effort [1]
= 60 N × 5 m = 300 J [1]
19. [2]
Efficiency = (Useful work output / Total work input) × 100% [1]
= (200 / 300) × 100% = 66.7% (or 67% to 2 s.f.) [1]
Marking note: Accept 66.67%, 66.7%, or 67%.
20. [2]
Power = Work / Time = 300 / 4 [1]
= 75 W [1]
Total: 40 marks