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Secondary 1 Science Practice Paper 1
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Questions
Secondary 1 Science Quiz - Physical Sciences
- Name: _______________________
- Class: _______________________
- Date: _______________________
- Score: ________/60 marks
- Duration: 40 minutes
- Total Marks: 60 marks
Instructions:
- Answer ALL questions.
- Write your answers in the spaces provided.
- Show all working for calculation questions.
- Use correct units where appropriate.
Section A: Multiple Choice and Short Response (Questions 1-8)[20 marks]
Answer ALL questions. Write your answers in the spaces provided.
1. Which of the following is a vector quantity? [2 marks]
A. Mass
B. Speed
C. Force
D. Energy
Answer: _______________________________
2. A student measures the mass of a book as 452 g using a top-pan balance. The balance has a zero error of +2 g. What is the actual mass of the book? [2 marks]
Answer: _______________________________
Working space:
3. State the energy conversion that occurs when a wind turbine generates electricity. [2 marks]
Answer: _______________________________
4. Explain the difference between a scalar quantity and a vector quantity. [2 marks]
5. A 50 g ball is dropped from a height of 2.0 m. Calculate the gravitational potential energy lost by the ball. (Take g = 10 N/kg) [3 marks]
Working space:
6. The diagram below shows four forces acting on a stationary box.
<image_placeholder> id: Q6-fig1 type: diagram linked_question: Q6 description: A rectangular box on a horizontal surface with four arrows representing forces. Arrow A points upward from the centre, labelled "A = 15 N". Arrow B points downward from the centre, labelled "B = 10 N". Arrow C points to the right, labelled "C = 8 N". Arrow D points to the left, labelled "D = 8 N". labels: Box, Surface, Force A (upward), Force B (downward), Force C (right), Force D (left), all with values in newtons values: A = 15 N, B = 10 N, C = 8 N, D = 8 N must_show: All four force arrows clearly labelled with directions and magnitudes; box centred on horizontal surface; arrows originating from or pointing toward the centre of the box </image_placeholder>
(a) Calculate the resultant force in the vertical direction. [1 mark]
Answer: _______________________________
(b) State whether the box will move horizontally. Explain your answer. [2 marks]
7. A student walks 3.0 km east, then 4.0 km north. [4 marks]
(a) Calculate the total distance travelled by the student. [1 mark]
Answer: _______________________________
(b) Calculate the magnitude of the student's displacement from the starting point. [2 marks]
Working space:
(c) State the difference between distance and displacement. [1 mark]
8. The diagram shows a simple pendulum at two different positions during its swing.
<image_placeholder> id: Q8-fig1 type: diagram linked_question: Q8 description: A simple pendulum showing two positions - position X at maximum height on left, position Y at lowest point of swing. Bob labelled at each position. Vertical reference line shown. Height difference between X and Y labelled as h = 0.20 m. Mass of bob = 0.50 kg. labels: Pivot point, String, Bob at position X, Bob at position Y, Reference line, h = 0.20 m, m = 0.50 kg values: h = 0.20 m, m = 0.50 kg, g = 10 N/kg (to be stated in question) must_show: Both positions clearly marked; bob drawn as circle; height difference labelled; string length consistent; vertical reference line </image_placeholder>
(a) Calculate the maximum gravitational potential energy of the bob relative to position Y. [2 marks]
Working space:
(b) State the kinetic energy of the bob at position Y, assuming no energy is lost. [1 mark]
Answer: _______________________________
Section B: Structured Questions (Questions 9-15)[24 marks]
Answer ALL questions. Write your answers in the spaces provided.
9. A car of mass 1200 kg accelerates from rest to a speed of 20 m/s in 10 s. [4 marks]
(a) Calculate the acceleration of the car. [2 marks]
(b) Calculate the force required to produce this acceleration. [2 marks]
10. The diagram shows an inclined plane used to raise a load.
<image_placeholder> id: Q10-fig1 type: diagram linked_question: Q10 description: A right-angled triangle representing an inclined plane. Vertical height = 1.5 m, horizontal length = 4.0 m, length along slope = 4.3 m. A box labelled "Load = 500 N" on the slope. Arrow along slope pointing up labelled "Effort force". Angle at base labelled θ. labels: Inclined plane, Load = 500 N, Effort force (arrow up slope), Vertical height = 1.5 m, Horizontal base = 4.0 m, Slope length = 4.3 m, Angle θ values: Height = 1.5 m, Base = 4.0 m, Slope = 4.3 m, Load = 500 N must_show: Right-angled triangle with all three sides labelled; box on slope; effort arrow along slope; all measurements clearly shown </image_placeholder>
(a) Calculate the work done against gravity to raise the load vertically by 1.5 m. [2 marks]
(b) Explain why the effort force needed to push the load up the slope is less than 500 N, even though the work done is the same (ignoring friction). [2 marks]
11. A student investigates the relationship between the extension of a spring and the force applied. The results are shown in the table below. [4 marks]
| Force (N) | 0 | 1.0 | 2.0 | 3.0 | 4.0 | 5.0 |
|---|---|---|---|---|---|---|
| Extension (cm) | 0 | 2.0 | 4.0 | 6.0 | 7.5 | 9.0 |
(a) On the grid below, plot a graph of extension against force. [2 marks]
<image_placeholder> id: Q11-fig1 type: graph linked_question: Q11 description: Blank graph grid for plotting extension (y-axis, 0 to 10 cm) against force (x-axis, 0 to 5 N). Grid lines at 0.5 N intervals horizontally and 1.0 cm intervals vertically. Axes labelled but no data plotted. labels: x-axis "Force (N)", y-axis "Extension (cm)", scale markers values: x-axis 0-5 N in 0.5 N steps, y-axis 0-10 cm in 1.0 cm steps must_show: Clear grid lines, labelled axes with units, proper scaling, sufficient space for all 6 data points </image_placeholder>
(b) Use your graph to determine the extension produced by a force of 2.5 N. [1 mark]
Answer: _______________________________
(c) The spring begins to deviate from Hooke's Law above a certain force. State the value of this force and explain how you determined this from the graph. [1 mark]
12. A block of ice of mass 0.40 kg at 0°C melts completely to form water at 0°C. [4 marks]
(a) State the energy change that takes place during melting. [1 mark]
(b) The specific latent heat of fusion of ice is 334 kJ/kg. Calculate the energy required to melt the ice. [2 marks]
(c) Explain why the temperature remains constant at 0°C during the melting process, even though energy is being supplied. [1 mark]
13. The diagram shows a crane lifting a load at constant velocity. [4 marks]
<image_placeholder> id: Q13-fig1 type: diagram linked_question: Q13 description: A crane with arm extending to the right, cable hanging vertically downward with a rectangular load at the end. Load labelled "800 kg". Cable labelled. Height of load above ground labelled "5.0 m". Small velocity arrow upward beside load with "v = 0.5 m/s constant". labels: Crane arm, Cable, Load = 800 kg, Height = 5.0 m, Constant velocity v = 0.5 m/s upward values: Mass = 800 kg, Height = 5.0 m, Velocity = 0.5 m/s upward must_show: Crane structure, vertical cable, rectangular load, height measurement from ground, velocity arrow with label </image_placeholder>
(a) Calculate the tension in the cable. (Take g = 10 N/kg) [2 marks]
(b) Explain why the power output of the crane's motor must be greater than the rate of increase of gravitational potential energy of the load. [2 marks]
14. A ball is thrown vertically upward with an initial velocity of 20 m/s. (Take g = 10 m/s², ignore air resistance) [4 marks]
(a) Calculate the maximum height reached by the ball. [2 marks]
(b) Calculate the time taken for the ball to return to the thrower's hand. [2 marks]
15. The diagram shows a lever in equilibrium. [4 marks]
<image_placeholder> id: Q15-fig1 type: diagram linked_question: Q15 description: A uniform metre rule pivoted at the 50 cm mark, balanced horizontally. A 2.0 N weight hangs from the 20 cm mark. An unknown force F hangs from the 80 cm mark. The rule is balanced horizontally. labels: Metre rule, Pivot at 50 cm mark, Weight = 2.0 N at 20 cm mark, Force F at 80 cm mark, All distances marked from pivot values: Pivot at 50 cm, 2.0 N at 20 cm (30 cm from pivot), F at 80 cm (30 cm from pivot) must_show: Horizontal rule with cm markings, clear pivot point, vertical arrows for forces, distance measurements from pivot clearly shown </image_placeholder>
(a) Calculate the moment of the 2.0 N weight about the pivot. [2 marks]
(b) Calculate the value of force F needed to balance the rule. [2 marks]
Section C: Longer Response (Questions 16-20)[16 marks]
Answer ALL questions. Write your answers in the spaces provided.
16. A student investigates how the speed of a trolley changes as it rolls down a ramp of different angles. [4 marks]
(a) State the independent variable, dependent variable, and one controlled variable in this investigation. [3 marks]
(b) Explain why releasing the trolley from the same point on the ramp each time is important. [1 mark]
17. The diagram shows a hydroelectric power station. [4 marks]
<image_placeholder> id: Q17-fig1 type: diagram linked_question: Q17 description: Cross-section diagram of a hydroelectric power station showing water reservoir at high elevation on left, dam wall, water flowing down pipe (penstock) to turbine building at lower level on right. Water exits from turbine to river at bottom right. Generator connected to turbine. Power lines extending from generator building. Labels for each component. labels: Reservoir, Dam wall, Penstock (pipe), Turbine, Generator, Power lines, River values: Height difference between reservoir and turbine = 80 m (labelled) must_show: Water level in reservoir, vertical drop to turbine, all main components labelled, flow direction indicated </image_placeholder>
(a) State the main energy conversions that take place from the water in the reservoir to electricity delivered to homes. [2 marks]
(b) Explain one advantage of hydroelectric power compared to fossil fuel power stations. [1 mark]
(c) Explain why the location of a hydroelectric power station is limited by geographical features. [1 mark]
18. A 60 kg student climbs a flight of stairs that rises 4.0 m vertically in 8.0 s. [4 marks]
(a) Calculate the work done by the student against gravity. (Take g = 10 N/kg) [2 marks]
(b) Calculate the average power output of the student. [2 marks]
19. The diagram shows an experiment to investigate friction between a block and different surfaces. [4 marks]
<image_placeholder> id: Q19-fig1 type: experimental_setup linked_question: Q19 description: Horizontal surface with a rectangular wooden block connected by string over a pulley to a hanging weight holder. Force meter (spring balance) shown in alternative arrangement pulling block horizontally. Three different surfaces shown as options: rough sandpaper, smooth wood, polished metal. Protractor not needed. Ruler optional. labels: Wooden block, String, Pulley, Hanging masses/Spring balance, Surface options (sandpaper, wood, metal) values: Block mass = 0.50 kg (to be stated in question text) must_show: Horizontal arrangement, pulley at edge of table, block on surface, force measurement method, three surface types clearly distinguishable </image_placeholder>
(a) Describe how you would determine which surface produces the least friction, keeping the block and pulling method the same. [2 marks]
(b) Suggest why sandpaper produces more friction than polished metal. [1 mark]
(c) Explain how lubricating oil between two metal surfaces reduces friction. [1 mark]
20. A metal ball of mass 0.10 kg is swung in a horizontal circle of radius 0.50 m at a constant speed of 2.0 m/s. [4 marks]
(a) Calculate the kinetic energy of the ball. [2 marks]
(b) Explain why work is done by the string on the ball even though the speed remains constant. [2 marks]
END OF QUIZ
Answers
Secondary 1 Science Quiz - Physical Sciences: ANSWER KEY
Total Marks: 60 marks
Section A: Multiple Choice and Short Response
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.
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?
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.
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.
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.
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.
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").
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.
Section B: Structured Questions
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).
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.
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.
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.
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.
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.
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.
Section C: Longer Response
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.
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.
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.
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.
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.
END OF ANSWER KEY