Secondary 4 Combined Science Physics Language Use Quiz

Secondary 4 Combined Science Physics Quiz - Language Use (Answer Key)

Total Marks: 40

Section A: Scientific Terminology and Definitions

1. Define the term acceleration. [1]
Answer: The rate of change of velocity.
(Note: Must mention velocity, not speed.)

2. State the SI unit for pressure. [1]
Answer: Pascal (Pa) or N/m².

3. Distinguish between a scalar quantity and a vector quantity. Give one example of each. [2]
Answer:

• Scalar has magnitude only (e.g., speed, mass, distance). [1]
• Vector has both magnitude and direction (e.g., velocity, force, displacement). [1]

4. In the context of thermal physics, define specific heat capacity. [2]
Answer: The amount of thermal energy required to raise the temperature of 1 kg of a substance by 1°C (or 1 K). [2]
(1 mark for "1 kg", 1 mark for "1°C/K rise".)

5. What is meant by the term terminal velocity? [2]
Answer: The constant maximum velocity reached by a falling object when the air resistance (drag) equals the weight (gravitational force), resulting in zero net force/acceleration. [2]

6. Define electromotive force (e.m.f.) of a cell. [2]
Answer: The energy supplied by the source to drive a unit charge around a complete circuit. (Or: Work done per unit charge by the source). [2]

Section B: Structured Explanations and Descriptions

7. "The temperature of the water increased because heat flowed into it." Explain why "heat" is inappropriate and suggest a better term. [2]
Answer:

• "Heat" refers to thermal energy in transit. It is not a property stored in an object. [1]
• Better term: "Thermal energy" flowed into it, or "Energy" was transferred to it. [1]

8. Describe the motion of particles in a solid compared to a gas. [3]
Answer:

• Solid: Particles are closely packed in a regular arrangement, vibrate about fixed positions, and have strong forces of attraction. [1.5]
• Gas: Particles are far apart, move randomly at high speeds, and have negligible forces of attraction between them. [1.5]

9. Explain why a metal spoon feels colder than a wooden spoon at the same temperature. [3]
Answer:

• Metal is a better thermal conductor than wood. [1]
• When touched, heat flows faster from the hand to the metal spoon than to the wooden spoon. [1]
• This rapid loss of heat from the hand makes the metal feel colder. [1]

10. A car travels around a circular track at constant speed. Explain why it is accelerating. [2]
Answer:

• Velocity is a vector quantity (has direction). [1]
• Since the direction of motion is constantly changing, the velocity is changing, which means there is acceleration. [1]

11. Describe how a convection current is formed in a liquid heated from below. [3]
Answer:

• The liquid at the bottom heats up, expands, and becomes less dense. [1]
• The less dense hot liquid rises, and cooler, denser liquid sinks to replace it. [1]
• This continuous circulation creates a convection current. [1]

12. Explain why the sky appears blue, referring to scattering. [2]
Answer:

• Sunlight is scattered by molecules in the atmosphere. [1]
• Blue light has a shorter wavelength and is scattered more strongly than other colors (Rayleigh scattering). [1]

13. Explain the difference between current and potential difference. [3]
Answer:

• Current is the rate of flow of electric charge (measured in Amperes). [1]
• Potential difference is the work done per unit charge to move charge between two points (measured in Volts). [1]
• Current is the flow itself; PD is the energy difference driving the flow. [1]

Section C: Precision in Problem Solving and Data Interpretation

14. Measurement: 50.0 cm. State significant figures and implication. [2]
Answer:

• 3 significant figures. [1]
• Implies the instrument can measure to the nearest 0.1 cm (or 1 mm). [1]

15. Describe motion in first 5 seconds (Velocity 0 to 10 m/s linearly). [2]
Answer:

• The cyclist undergoes uniform (constant) acceleration. [1]
• The acceleration is calculated as gradient: (10-0)/5 = 2 m/s². [1]

16. Relationship between angle of incidence and refraction entering denser medium. [2]
Answer:

• The angle of refraction is smaller than the angle of incidence. [1]
• The light ray bends towards the normal. [1]

17. Calculate Power: I = 2.0 A, V = 12 V. [2]
Answer:

• Formula: P = VI [1]
• Calculation: P = 12 × 2.0 = 24 W. [1]

18. Calculate Work Done: F = 10 N, d = 5 m. [2]
Answer:

• Formula: W = F × d [1]
• Calculation: W = 10 × 5 = 50 J. [1]

19. Why is a fuse connected to the live wire? [2]
Answer:

• To disconnect the high potential (live) supply from the appliance when the fuse blows. [1]
• If connected to neutral, the appliance would still be live (at high potential) even after the fuse blows, posing a shock hazard. [1]

20. Correct "Weight and mass are the same." [2]
Answer:

• Mass is the amount of matter in an object (kg); Weight is the gravitational force acting on it (N). [1]
• They are different physical quantities with different units. [1]