Secondary 1 Science Practice Paper 1

Secondary 1 Science Quiz - Physical Sciences: ANSWER KEY

Total Marks: 60 marks

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Section A: Multiple Choice and Short Response

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1. [2 marks]

Answer: C (Force) [2 marks]

Explanation: A vector quantity has both magnitude and direction.

• Mass (A) is a scalar – it has only magnitude (e.g., 5 kg) with no direction.
• Speed (B) is a scalar – it tells us how fast something moves but not in which direction.
• Force (C) is a vector – it has magnitude (e.g., 10 N) and acts in a specific direction (e.g., to the right). [1 mark for correct choice]
• Energy (D) is a scalar – it has magnitude only (e.g., 50 J).

Teaching note: Remember the key test: "Does it have a direction?" If yes, it's a vector. Common vectors in Sec 1: force, velocity, displacement, acceleration, weight. Common scalars: mass, speed, distance, energy, temperature, time.

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2. [2 marks]

Answer: 450 g [2 marks]

Working:

• Reading on balance = 452 g
• Zero error = +2 g (reads 2 g too high)
• Actual mass = 452 g − 2 g = 450 g [1 mark for method, 1 mark for answer]

Teaching note: A positive zero error means the instrument reads higher than the true value, so we subtract. If the zero error were negative (−2 g), we would add. Always check: does the reading need to be corrected up or down?

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3. [2 marks]

Answer: Kinetic energy of wind → Mechanical energy of turbine blades → Electrical energy [2 marks]

Marking breakdown:

• Kinetic energy of wind → mechanical/kinetic energy of turbine [1 mark]
• Mechanical energy → electrical energy [1 mark]

Teaching note: Remember that energy cannot be created or destroyed, only converted. The wind has kinetic energy due to air movement; this turns the blades (mechanical energy), which spin a generator to produce electricity. Avoid saying "wind energy" as this is vague – specify kinetic energy.

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4. [2 marks]

Answer: A scalar quantity has magnitude only; a vector quantity has both magnitude and direction. [2 marks]

Marking breakdown:

• Scalar has magnitude only [1 mark]
• Vector has magnitude and direction [1 mark]

Teaching note: Examples help fix this: scalar = 5 kg (just a number with unit); vector = 5 N to the left (needs number, unit, AND direction). Weight is a vector (gravitational force acting downward); mass is a scalar.

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5. [3 marks]

Answer: Gravitational potential energy lost = 1.0 J [3 marks]

Working:

• Formula: GPE = mgh [0.5 mark]
• m = 50 g = 0.050 kg (convert to kg!) [0.5 mark]
• g = 10 N/kg
• h = 2.0 m
• GPE = 0.050 × 10 × 2.0 = 1.0 J [1.5 marks for substitution and calculation]

Teaching note: Common error: forgetting to convert grams to kilograms. In physics formulas, mass must be in kg for SI units. Another check: 50 g is very light and 2 m is moderate, so 1 J is reasonable. If you got 1000 J, you used 50 kg instead of 0.050 kg.

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6. [3 marks]

(a) [1 mark]

Answer: Resultant vertical force = 15 − 10 = 5 N upward [1 mark]

(b) [2 marks]

Answer: The box will not move horizontally. [1 mark] The horizontal forces C and D are equal in magnitude (8 N) but opposite in direction, so they cancel out (resultant horizontal force = 0). [1 mark]

Teaching note: For equilibrium, resultant force must be zero in all directions. The box is NOT in vertical equilibrium (5 N upward resultant), so it may accelerate upward or be about to lift off if this exceeds the normal reaction. The question tests whether you analyse each direction separately.

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7. [4 marks]

(a) [1 mark]

Answer: Total distance = 3.0 + 4.0 = 7.0 km [1 mark]

(b) [2 marks]

Working:

• Displacement forms the hypotenuse of a right-angled triangle.
• Using Pythagoras: displacement = √(3.0² + 4.0²) [1 mark]
• = √(9.0 + 16.0) = √25.0 = 5.0 km [1 mark]

(c) [1 mark]

Answer: Distance is the total path length travelled (scalar); displacement is the straight-line distance from start to finish with direction (vector). [1 mark]

Teaching note: Always draw the vector diagram for displacement problems. The 3-4-5 triangle is common in exams. Displacement needs a direction for full marks in some contexts (e.g., "5.0 km at 053°" or "5.0 km northeast").

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8. [3 marks]

(a) [2 marks]

Working:

• Formula: GPE = mgh [0.5 mark]
• m = 0.50 kg, g = 10 N/kg, h = 0.20 m
• GPE = 0.50 × 10 × 0.20 = 1.0 J [1.5 marks for substitution and calculation]

(b) [1 mark]

Answer: 1.0 J [1 mark]

Explanation: By conservation of energy, all GPE at the highest point converts to kinetic energy at the lowest point (assuming no air resistance). This is a key principle: total mechanical energy is conserved in an ideal system.

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Section B: Structured Questions

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9. [4 marks]

(a) [2 marks]

Working:

• Formula: a = (v − u)/t [0.5 mark]
• u = 0 m/s (from rest), v = 20 m/s, t = 10 s
• a = (20 − 0)/10 = 2.0 m/s² [1.5 marks for substitution and answer]

(b) [2 marks]

Working:

• Formula: F = ma [0.5 mark]
• m = 1200 kg, a = 2.0 m/s²
• F = 1200 × 2.0 = 2400 N [1.5 marks for substitution and answer]

Teaching note: These are the two fundamental equations of motion for constant acceleration. Remember: F = ma means force causes acceleration. Direction matters – if slowing down, acceleration would be negative (deceleration).

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10. [4 marks]

(a) [2 marks]

Working:

• Work done = force × vertical distance moved in direction of force
• = weight × height = 500 N × 1.5 m [1 mark]
• = 750 J [1 mark]

(b) [2 marks]

Answer: The effort force is applied over a longer distance (4.3 m along slope vs 1.5 m vertically). [1 mark] Since work = force × distance, for the same work (750 J), a smaller force acting over a longer distance produces the same work as a larger force acting over a shorter distance. [1 mark]

Teaching note: This is the principle of simple machines: they multiply force at the expense of distance. The inclined plane is a force multiplier. Without friction: effort × slope length = load × vertical height.

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11. [4 marks]

(a) [2 marks]

Expected graph: Points plotted at (0,0), (1,2), (2,4), (3,6), (4,7.5), (5,9.0) with best-fit straight line through first four points, then curve/change of gradient. [2 marks for correct plotting and line]

Marking breakdown:

• All 6 points correctly plotted [1 mark]
• Best-fit line showing change at or near 3.0 N [1 mark]

(b) [1 mark]

Answer: From graph: 5.0 cm (accept 4.8–5.2 cm) [1 mark]

(c) [1 mark]

Answer: 3.0 N [0.5 mark]. Above this force, the graph curves/is no longer a straight line through the origin/proportionality is lost [0.5 mark].

Teaching note: Hooke's Law states F = kx (extension proportional to force) valid only within the limit of proportionality. The point where the graph deviates from straight-line marks this limit. Never say "spring breaks" – it hasn't broken, just exceeded its elastic limit.

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12. [4 marks]

(a) [1 mark]

Answer: Latent heat / thermal energy is absorbed to overcome bonds between molecules; internal potential energy increases. [1 mark]

(b) [2 marks]

Working:

• Formula: Q = ml [0.5 mark]
• m = 0.40 kg, l = 334 kJ/kg = 334 000 J/kg
• Q = 0.40 × 334 000 = 133 600 J or 134 kJ or 1.34 × 10⁵ J [1.5 marks]

(c) [1 mark]

Answer: The energy supplied is used to break intermolecular bonds / increase separation between molecules (increase potential energy) rather than increase kinetic energy of molecules. [1 mark] Since temperature depends on average kinetic energy, temperature stays constant during phase change.

Teaching note: "Latent" means hidden – the energy seems to disappear because there's no temperature change, but it's doing internal work against molecular forces. This is why melting ice at 0°C needs energy but stays at 0°C.

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13. [4 marks]

(a) [2 marks]

Working:

• At constant velocity, upward force (tension) = downward force (weight) [0.5 mark]
• Weight = mg = 800 × 10 = 8000 N [1 mark]
• Tension = 8000 N [0.5 mark]

(b) [2 marks]

Answer: The motor must also do work against: [1 mark for any one]

• Friction in the pulley system / cable
• Air resistance on the load
• Moving parts of the crane itself
• Inefficiency/heat in the motor [1 mark]

Teaching note: "Constant velocity" is the key phrase telling us ΣF = 0 (Newton's First Law). Don't be tempted to add extra force "to keep it moving" – that's Aristotelian physics, not Newtonian! The power is greater because of energy losses, not because more force is needed to accelerate.

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14. [4 marks]

(a) [2 marks]

Working:

• At maximum height, final velocity v = 0
• Using: v² = u² + 2as, where a = −g = −10 m/s² [0.5 mark]
• 0 = (20)² + 2(−10)s [0.5 mark]
• 0 = 400 − 20s
• 20s = 400, s = 20 m [1 mark]

(b) [2 marks]

Working:

• Time to reach maximum height: v = u + at [0.5 mark]
• 0 = 20 + (−10)t, t = 2.0 s [0.5 mark]
• By symmetry (same path down), total time = 2.0 + 2.0 = 4.0 s [1 mark]

Alternative working for (b): Using s = ut + ½at² with s = 0 (returns to start):

• 0 = 20t + ½(−10)t² → 0 = 20t − 5t² → 5t(4 − t) = 0 → t = 0 or t = 4.0 s

Teaching note: The symmetry of vertical motion under gravity is powerful – time up equals time down, and speed of return equals speed of projection (without air resistance). Always draw the velocity-time triangle to visualise.

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15. [4 marks]

(a) [2 marks]

Working:

• Moment = force × perpendicular distance from pivot [0.5 mark]
• Distance = 50 − 20 = 30 cm = 0.30 m [0.5 mark]
• Moment = 2.0 × 0.30 = 0.60 N m (anticlockwise) [1 mark]

(b) [2 marks]

Working:

• For equilibrium: sum of clockwise moments = sum of anticlockwise moments [0.5 mark]
• F × (80 − 50) = 2.0 × (50 − 20) [0.5 mark]
• F × 0.30 = 2.0 × 0.30
• F = 2.0 N [1 mark]

Teaching note: The principle of moments: balanced lever means no net turning effect. Always measure distances from the pivot, not from the ends. The unit is N m (newton-metre), not N/m or m/N. Notice this is a balanced lever because both forces are equidistant from pivot with equal magnitudes.

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Section C: Longer Response

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16. [4 marks]

(a) [3 marks]

Independent variable: Angle of the ramp / steepness of ramp [1 mark]
Dependent variable: Speed of trolley / time to travel fixed distance [1 mark]
Controlled variable: Any one from: same trolley, same starting position, same ramp surface, same distance measured [1 mark]

(b) [1 mark]

Answer: To ensure the same initial gravitational potential energy / height / starting energy each time; this makes the investigation a fair test. [1 mark]

Teaching note: "Fair test" is the key concept in scientific inquiry. Only ONE variable should change. If starting position varies, initial GPE varies, so speed changes for two reasons, making conclusions invalid.

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17. [4 marks]

(a) [2 marks]

Answer:

• GPE of water in reservoir → KE of flowing water [0.5 mark]
• KE of water → mechanical KE of turbine blades [0.5 mark]
• Mechanical energy of turbine → electrical energy in generator [0.5 mark]
• Electrical energy transmitted via power lines [0.5 mark]

(b) [1 mark]

Answer: Any one from: renewable/does not run out; no greenhouse gas emissions during operation; no air pollution; low running costs once built [1 mark]

(c) [1 mark]

Answer: Requires a suitable river with sufficient water flow; needs a valley to dam for reservoir; requires sufficient height difference/head for adequate water pressure. [1 mark]

Teaching note: Hydroelectric is excellent for base-load power in suitable locations, but geography-dependent. Pumped storage (reversible turbines) can store energy by pumping water uphill when demand is low.

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18. [4 marks]

(a) [2 marks]

Working:

• Weight = mg = 60 × 10 = 600 N [0.5 mark]
• Work = force × distance = 600 × 4.0 [0.5 mark]
• = 2400 J [1 mark]

(b) [2 marks]

Working:

• Formula: Power = work done / time taken [0.5 mark]
• = 2400 / 8.0 [0.5 mark]
• = 300 W [1 mark]

Teaching note: 300 W is about half a horsepower – reasonable for a short burst of stair climbing. For comparison, a fit human can sustain ~100 W for long periods. Always check that working makes physical sense.

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19. [4 marks]

(a) [2 marks]

Answer: Place the block on each surface in turn. Pull the block at constant speed using the spring balance. [1 mark] The surface requiring the smallest force reading to maintain constant speed has the least friction. [1 mark]

(b) [1 mark]

Answer: Sandpaper has a rougher surface / more irregularities / greater surface roughness at microscopic level, leading to more interlocking and contact points between surfaces. [1 mark]

(c) [1 mark]

Answer: Oil fills irregularities on surfaces / separates the surfaces with a fluid layer / reduces direct contact between surfaces, so interlocking is reduced. [1 mark]

Teaching note: Friction arises from two main factors: surface roughness (mechanical interlocking) and adhesive forces between molecules. Lubrication addresses both by providing a slippery separating layer.

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20. [4 marks]

(a) [2 marks]

Working:

• Formula: KE = ½mv² [0.5 mark]
• = ½ × 0.10 × (2.0)² [0.5 mark]
• = ½ × 0.10 × 4.0 = 0.20 J [1 mark]

(b) [2 marks]

Answer: The string exerts a force toward the centre of the circle (centripetal force). [1 mark] Although speed is constant, velocity is changing (direction changes continuously), so there is acceleration toward the centre. Work = force × displacement in direction of force; the force is always perpendicular to velocity, so no work is done in direction of motion, but the explanation tests understanding that circular motion requires continuous force. [1 mark for circular motion explanation]

Correction/Clarification for teaching: Actually, in ideal uniform circular motion, the tension does NO work on the ball because force is always perpendicular to displacement. However, the student needs to explain that:

• A force IS needed to change direction (Newton's First Law: without force, straight-line motion)
• The speed stays constant because tension is perpendicular to velocity
• Energy stays constant, so KE is constant

Accept answers that recognise the tension's role in changing direction while not changing speed/energy. [2 marks for clear explanation of direction change without energy change]

Teaching note: This is a subtle point. Work = Fd cos θ. In circular motion, θ = 90°, so cos 90° = 0. No work, no energy change, but force is essential for circular motion. Don't say "force keeps it moving" – force changes direction.

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END OF ANSWER KEY