Chapter 1 : Physical Quantities and Measurement

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Chapter Overview & SLOs

What is physics? Chapter 1, "Physical Quantities and Measurement," establishes the foundation for studying physics, which is defined as the study of matter and energy. This chapter answers fundamental questions about how physical quantities are measured and expressed. What are the branches of physics? You will explore various branches of physics including: - Mechanics: Study of motion and forces - Thermodynamics: Study of heat and temperature - Electromagnetism: Study of electric and magnetic fields - Optics: Study of light and its behavior - Nuclear Physics: Study of atomic nucleus and radioactive decay - Quantum Physics: Study of matter and energy at atomic scales The chapter highlights how these principles drive modern technologies like PET scans, MRI machines, lasers, and space exploration. What are base and derived physical quantities? You will learn to distinguish between: - Base Physical Quantities: Fundamental quantities that cannot be defined in terms of other quantities. Seven base quantities: Length (meter), Mass (kilogram), Time (second), Electric Current (ampere), Temperature (kelvin), Amount of Substance (mole), Luminous Intensity (candela). - Derived Physical Quantities: Quantities derived from base quantities. Examples: Force (newton = kg·m/s²), Pressure (pascal = N/m²), Energy (joule = N·m), Power (watt = J/s), Velocity (m/s), Acceleration (m/s²), Density (kg/m³). How do we use prefixes and scientific notation? The notes provide practical guidance on using prefixes and scientific notation to handle very large or small measurements: - Prefixes: pico (p = 10⁻¹²), nano (n = 10⁻⁹), micro (µ = 10⁻⁶), milli (m = 10⁻³), centi (c = 10⁻²), kilo (k = 10³), mega (M = 10⁶), giga (G = 10⁹), tera (T = 10¹²) - Scientific Notation: Expressing numbers as a × 10ⁿ where 1 ≤ a < 10. Example: 0.000025 = 2.5 × 10⁻⁵, 5,600,000 = 5.6 × 10⁶ What are measuring instruments and how do we use them? A major focus is placed on precision instruments: - Vernier Calipers: Used to measure length up to 0.1 mm precision. Main scale + Vernier scale. Least count = 0.1 mm (0.01 cm). - Screw Gauge (Micrometer): Used to measure thickness up to 0.01 mm precision. Main scale + circular scale. Least count = 0.01 mm (0.001 cm). - Zero Error Correction: Positive zero error occurs when zero of circular scale is below reference line (subtract error). Negative zero error occurs when zero of circular scale is above reference line (add error). - Measuring Cylinder: Used to measure volume of liquids. Meniscus reading at eye level. - Stopwatch: Used to measure time intervals. Digital stopwatches measure to 0.01 s. What are measurement errors? The chapter covers: - Random Errors: Unpredictable fluctuations (due to observer's estimation, environmental changes). Can be reduced by taking multiple readings and averaging. - Systematic Errors: Consistent errors in one direction (due to faulty instruments, incorrect calibration). Can be eliminated by zero error correction or using calibrated instruments. - Precision vs Accuracy: Precision refers to consistency of measurements (closeness of repeated readings). Accuracy refers to closeness to true value. - Significant Figures: All reliably known digits in a measurement plus one estimated digit. Rules: Non-zero digits are always significant, zeros between non-zero digits are significant, leading zeros are not significant, trailing zeros after decimal are significant. What are scalars and vectors? You will learn the fundamental distinction: - Scalars: Physical quantities with only magnitude (size). Examples: mass, length, time, speed, distance, energy, temperature, pressure. - Vectors: Physical quantities with both magnitude and direction. Examples: displacement, velocity, acceleration, force, weight, momentum, torque. These notes are strictly aligned with the Student Learning Outcomes (SLOs) for the FBISE 2026 annual examination.

• What is physics and what are its branches? Define physics as the study of matter and energy, describe its various branches (Mechanics, Thermodynamics, Electromagnetism, Optics, Nuclear Physics, Quantum Physics), and explain the role of physics in the development of technology and society including PET scans, MRI, lasers, and space exploration.
• What are base and derived physical quantities? Distinguish between base physical quantities (seven base quantities: length, mass, time, electric current, temperature, amount of substance, luminous intensity) and derived physical quantities (force, pressure, energy, power, velocity, acceleration, density) with their SI units, and use prefixes (pico to tera) and scientific notation in measurements.
• What are measuring instruments and how do we calculate least count? Describe the construction and working of measuring instruments (Vernier calipers with least count 0.1 mm, screw gauge with least count 0.01 mm, stopwatch, measuring cylinder) and calculate their least counts, including zero error correction for positive and negative zero errors.
• What are measurement errors and the difference between scalars and vectors? Analyze measurement errors including random errors (unpredictable, reduced by averaging) and systematic errors (consistent, eliminated by calibration), explain the concepts of precision (consistency) and accuracy (closeness to true value) and significant figures, and differentiate between scalars (magnitude only - mass, length, time, speed) and vectors (magnitude and direction - displacement, velocity, acceleration, force).

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