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Secondary 4 Combined Science Physics Practice Paper 3

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TuitionGoWhere Practice Paper - Combined Science Physics Secondary 4

TuitionGoWhere Practice Paper (AI)

Subject: Combined Science (Physics)
Level: Secondary 4
Paper: Practice Paper (Version 3 of 5)
Duration: 1 hour 15 minutes
Total Marks: 65

Name: __________________________
Class: __________________________
Date: __________________________

Instructions to Candidates

Write your name, class, and date in the spaces provided.
Answer all questions.
Write your answers in the spaces provided on the question paper.
You may use an approved scientific calculator where appropriate.
Take $g = 10 \text{ N/kg}$ and the speed of light in vacuum $c = 3.0 \times 10^8 \text{ m/s}$ unless otherwise stated.
The total mark for this paper is 65.

Section A: Multiple Choice & Structured Questions (20 Marks)

1. A student measures the diameter of a wire using a micrometer screw gauge. The main scale reading is 2.5 mm and the thimble scale reading is 0.18 mm. What is the diameter of the wire?
[1]

A. 2.32 mm
B. 2.50 mm
C. 2.68 mm
D. 4.30 mm

Answer: __________________________

2. Which of the following quantities is a vector?
[1]

A. Speed
B. Distance
C. Mass
D. Acceleration

Answer: __________________________

3. A car travels at a constant speed of 20 m/s around a circular track. Which statement is correct?
[1]

A. The velocity is constant because the speed is constant.
B. The acceleration is zero because the speed is constant.
C. The velocity is changing because the direction is changing.
D. The acceleration is constant in direction.

Answer: __________________________

4. A block of mass 5.0 kg is pushed across a horizontal floor with a force of 20 N. The block moves at a constant velocity. What is the magnitude of the frictional force acting on the block?
[1]

A. 0 N
B. 5.0 N
C. 20 N
D. 50 N

Answer: __________________________

5. Which of the following best describes the arrangement and motion of particles in a liquid?
[1]

A. Particles are closely packed in a regular pattern and vibrate about fixed positions.
B. Particles are far apart and move randomly at high speeds.
C. Particles are close together but can slide past one another.
D. Particles are arranged in layers and do not move.

Answer: __________________________

6. A ray of light travels from air into a glass block. The angle of incidence is $40^\circ$ and the angle of refraction is $25^\circ$ . What happens to the speed and wavelength of the light as it enters the glass?
[1]

	Speed	Wavelength
A	Decreases	Decreases
B	Decreases	Increases
C	Increases	Decreases
D	Increases	Increases

Answer: __________________________

7. Which region of the electromagnetic spectrum is used for satellite communications?
[1]

A. Infrared
B. Microwaves
C. Ultraviolet
D. X-rays

Answer: __________________________

8. Two resistors of resistance $4.0 \, \Omega$ and $6.0 \, \Omega$ are connected in series. What is the total resistance?
[1]

A. $2.4 \, \Omega$
B. $4.0 \, \Omega$
C. $6.0 \, \Omega$
D. $10.0 \, \Omega$

Answer: __________________________

9. In a domestic electrical circuit, why is the fuse connected to the live wire?
[1]

A. To ensure the circuit is disconnected from the high voltage supply if the fuse blows.
B. To prevent the neutral wire from overheating.
C. To allow the earth wire to carry current during normal operation.
D. To reduce the power consumption of the appliance.

Answer: __________________________

10. A transformer has 100 turns on the primary coil and 200 turns on the secondary coil. If the input voltage is 12 V a.c., what is the output voltage?
[1]

A. 6 V
B. 12 V
C. 24 V
D. 48 V

Answer: __________________________

Section B: Structured Questions (30 Marks)

11. A cyclist travels along a straight road. The velocity-time graph for the first 20 seconds of the journey is shown below.

(Imagine a graph: Velocity starts at 0 m/s at t=0, increases linearly to 10 m/s at t=10s, remains constant at 10 m/s from t=10s to t=15s, then decreases linearly to 0 m/s at t=20s.)

(a) Describe the motion of the cyclist between $t = 0$ s and $t = 10$ s.
[1]

(b) Calculate the acceleration of the cyclist between $t = 0$ s and $t = 10$ s.
[2]

<br> <br> <br>

(c) Calculate the total distance traveled by the cyclist during the 20 seconds.
[3]

<br> <br> <br> <br> <br>

12. A student investigates the principle of moments using a uniform meter rule pivoted at its center (50 cm mark).

(a) State the principle of moments.
[2]

(b) A weight of 2.0 N is hung at the 20 cm mark. Calculate the moment of this force about the pivot.
[2]

<br> <br> <br>

(c) Where must a 4.0 N weight be hung to balance the rule?
[2]

<br> <br> <br>

13. A metal block of mass 0.5 kg is heated using an immersion heater. The specific heat capacity of the metal is $400 \text{ J/(kg}^\circ\text{C)}$ .

(a) Define specific heat capacity.
[2]

(b) Calculate the thermal energy required to raise the temperature of the block from $20^\circ\text{C}$ to $70^\circ\text{C}$ .
[3]

<br> <br> <br> <br> <br>

(c) In practice, the heater supplies more energy than calculated in (b). Suggest one reason for this difference.
[1]

14. Fig. 14.1 shows a ray of light entering a semi-circular glass block. The light travels along the radius towards the center of the flat edge.

(Diagram description: Ray enters curved surface, travels to center of flat face. Angle of incidence at flat face is $30^\circ$ . Critical angle for glass is $42^\circ$ .)

(a) Explain why the ray does not refract when it enters the curved surface of the block.
[1]

(b) The angle of incidence at the flat surface is increased to $50^\circ$ .
(i) Name the phenomenon that occurs at the flat surface.
[1]

(ii) State two conditions necessary for this phenomenon to occur.
[2]

15. A simple a.c. generator consists of a coil rotating in a magnetic field.

(a) State Faraday’s Law of electromagnetic induction.
[2]

(b) Suggest two ways to increase the magnitude of the induced e.m.f. in the generator.
[2]

Section C: Free Response Questions (15 Marks)

16. A skydiver jumps from a stationary helicopter.

(a) Explain, in terms of forces, why the skydiver accelerates downwards immediately after jumping.
[2]

(b) As the skydiver falls, her speed increases. Explain why her acceleration decreases as her speed increases.
[3]

(c) Eventually, the skydiver reaches a constant speed known as terminal velocity.
(i) State the value of the resultant force acting on the skydiver at terminal velocity.
[1]

(ii) The skydiver opens her parachute. Explain why she slows down.
[2]

17. Fig. 17.1 shows a circuit containing a battery, a switch, a fixed resistor $R$ , and a thermistor $T$ connected in series. A voltmeter is connected across the thermistor.

(Diagram: Battery -> Switch -> Resistor R -> Thermistor T -> Battery. Voltmeter in parallel with T.)

(a) Describe how the resistance of the thermistor changes as the temperature increases.
[1]

(b) The temperature of the thermistor increases.
(i) State and explain what happens to the current in the circuit.
[2]

(ii) State and explain what happens to the reading on the voltmeter.
[2]

(c) Suggest one practical application of this circuit.
[1]

18. A transformer is used to step down the voltage from 240 V to 12 V for a laptop charger.

(a) Explain why a transformer cannot work with a d.c. supply.
[2]

(b) The primary coil has 2000 turns. Calculate the number of turns on the secondary coil.
[2]

<br> <br> <br>

(c) The laptop draws a current of 2.0 A at 12 V. Assuming the transformer is 100% efficient, calculate the current in the primary coil.
[2]

<br> <br> <br>

Answers

TuitionGoWhere Practice Paper - Combined Science Physics Secondary 4

Answer Key & Marking Scheme (Version 3)

Section A: Multiple Choice (10 Marks)

1. C
Reasoning: Diameter = Main scale + Thimble scale = $2.5 \text{ mm} + 0.18 \text{ mm} = 2.68 \text{ mm}$ .

2. D
Reasoning: Acceleration has both magnitude and direction. Speed, distance, and mass are scalars.

3. C
Reasoning: Velocity is a vector. Even if speed is constant, changing direction means velocity changes.

4. C
Reasoning: Constant velocity implies equilibrium (Newton's 1st Law). Therefore, Friction = Applied Force = 20 N.

5. C
Reasoning: In liquids, particles are close together (high density) but have enough energy to slide past each other (fluidity).

6. A
Reasoning: When light enters a denser medium (glass), it slows down. Since $v = f\lambda$ and frequency $f$ is constant, wavelength $\lambda$ must decrease.

7. B
Reasoning: Microwaves are used for satellite communications and radar.

8. D
Reasoning: Series resistance $R_{total} = R_1 + R_2 = 4.0 + 6.0 = 10.0 \, \Omega$ .

9. A
Reasoning: The fuse must be on the live wire so that if it blows, the appliance is disconnected from the high voltage, preventing electric shock.

10. C
Reasoning: $\frac{V_s}{V_p} = \frac{N_s}{N_p} \Rightarrow V_s = 12 \times \frac{200}{100} = 24 \text{ V}$ .

Section B: Structured Questions (30 Marks)

11. Kinematics

(a) The cyclist accelerates uniformly / at a constant acceleration. [1]
(Note: "Speeds up" is acceptable but "accelerates" is precise.)

(b) Acceleration $a = \frac{\Delta v}{\Delta t}$ [1]
$a = \frac{10 - 0}{10 - 0} = 1.0 \text{ m/s}^2$ [1]

(c) Distance = Area under the graph. [1]
Area 1 (Triangle, 0-10s): $\frac{1}{2} \times 10 \times 10 = 50 \text{ m}$
Area 2 (Rectangle, 10-15s): $5 \times 10 = 50 \text{ m}$
Area 3 (Triangle, 15-20s): $\frac{1}{2} \times 5 \times 10 = 25 \text{ m}$ [1 for correct areas]
Total Distance = $50 + 50 + 25 = 125 \text{ m}$ [1]

12. Moments

(a) For an object in equilibrium, the sum of clockwise moments about a pivot is equal to the sum of anticlockwise moments about the same pivot. [2]
(1 mark for "clockwise = anticlockwise", 1 mark for "about a pivot/equilibrium".)

(b) Distance from pivot = $50 \text{ cm} - 20 \text{ cm} = 30 \text{ cm} = 0.3 \text{ m}$ . [1]
Moment = Force $\times$ perpendicular distance
Moment = $2.0 \times 0.3 = 0.6 \text{ Nm}$ . [1]

(c) Clockwise Moment = Anticlockwise Moment
$0.6 \text{ Nm} = 4.0 \text{ N} \times d$ [1]
$d = \frac{0.6}{4.0} = 0.15 \text{ m} = 15 \text{ cm}$ .
Position on rule = $50 \text{ cm} + 15 \text{ cm} = 65 \text{ cm}$ mark. [1]
(Note: Answer "15 cm from pivot" is also acceptable if position is not explicitly asked as a mark on the rule, but "65 cm mark" is precise.)

13. Thermal Physics

(a) Specific heat capacity is the amount of thermal energy required to raise the temperature of 1 kg of a substance by $1^\circ\text{C}$ (or 1 K). [2]

(b) $\Delta \theta = 70 - 20 = 50^\circ\text{C}$ . [1]
$E = mc\Delta \theta$
$E = 0.5 \times 400 \times 50$ [1]
$E = 10,000 \text{ J}$ (or 10 kJ). [1]

(c) Energy is lost to the surroundings / air / heater casing. [1]
(Or: The heater itself absorbs some energy.)

14. Light

(a) The ray enters along the normal (perpendicular to the surface), so the angle of incidence is $0^\circ$ . Therefore, it does not refract. [1]

(b)(i) Total Internal Reflection (TIR). [1]

(b)(ii)

Light must travel from a denser medium (glass) to a less dense medium (air). [1]
The angle of incidence must be greater than the critical angle. [1]

15. Electromagnetism

(a) The induced e.m.f. is proportional to the rate of change of magnetic flux linkage (or rate of cutting of magnetic field lines). [2]
(Accept: "Magnitude of induced e.m.f. depends on how fast the magnetic field changes/cuts the coil.")

(b) Any two of:

Increase the speed of rotation. [1]
Use a stronger magnet. [1]
Increase the number of turns on the coil. [1]
Increase the area of the coil. [1]

Section C: Free Response Questions (15 Marks)

16. Dynamics & Forces

(a) Immediately after jumping, the only significant force acting is weight (gravity) downwards. Air resistance is negligible/zero. Therefore, there is a resultant downward force, causing acceleration. [2]

(b) As speed increases, air resistance (drag) increases. [1]
The resultant force ( $Weight - Air Resistance$ ) decreases. [1]
Since $F=ma$ , as the resultant force decreases, the acceleration decreases. [1]

(c)(i) Resultant force = 0 N. [1]

(c)(ii) Opening the parachute greatly increases the surface area, which significantly increases air resistance. [1]
The air resistance becomes greater than the weight, creating a resultant upward force, which causes deceleration (slowing down). [1]

17. Electricity

(a) The resistance of the thermistor decreases as temperature increases. [1]

(b)(i) The total resistance of the circuit decreases (because $R_{thermistor}$ decreases). [1]
Therefore, the current in the circuit increases ( $I = V/R$ ). [1]

(b)(ii) The voltmeter reading decreases. [1]
Reason: The current increases, so the potential difference across the fixed resistor $R$ increases ( $V=IR$ ). Since the supply voltage is constant, the p.d. across the thermistor must decrease. [1]
(Alternative Reason: $V_{thermistor} = I \times R_{thermistor}$ . Although $I$ increases, $R_{thermistor}$ decreases more significantly, or simply use potential divider principle: $R_{thermistor}$ is a smaller fraction of total R.)

(c) Fire alarm / Temperature control switch / Thermostat. [1]

18. Transformers

(a) A transformer works on the principle of electromagnetic induction, which requires a changing magnetic field. [1]
D.C. produces a constant magnetic field, so there is no change in flux linkage and no e.m.f. is induced in the secondary coil. [1]

(b) $\frac{V_s}{V_p} = \frac{N_s}{N_p}$
$\frac{12}{240} = \frac{N_s}{2000}$ [1]
$N_s = \frac{12 \times 2000}{240} = 100$ turns. [1]

(c) Power Input = Power Output (100% efficient)
$V_p I_p = V_s I_s$
$240 \times I_p = 12 \times 2.0$ [1]
$240 I_p = 24$
$I_p = \frac{24}{240} = 0.1 \text{ A}$ . [1]