Lesson Overview

Unit 1 introduces the foundations of physics as an experimental science. Students learn about physical quantities, SI units, dimensions, measurement instruments, errors, vectors, and graphical interpretation—skills essential for all future physics lessons.

1. Core Concepts (Short Notes)

1.1 Nature & Scope of Physics

• Physics: Study of energy, matter, and their interactions.

• Applications: Transport, communication, medical imaging, power generation, space science.

• Scientific Method:

  1. Observation

  2. Hypothesis

  3. Experiment

  4. Theory/Law

  5. Prediction

1.2 Physical Quantities & SI Units

Types of quantities:

• Fundamental: Mass (kg), Length (m), Time (s), Temperature (K), Electric current (A), Amount of substance (mol), Luminous intensity (cd).

• Derived: Speed (m/s), Force (N), Pressure (Pa), Energy (J), Power (W), Charge (C).

SI Prefixes: milli (m), micro (µ), kilo (k), mega (M), etc.

1.3 Dimensions & Dimensional Analysis

• Dimensions indicate how a physical quantity depends on basic quantities.

• Basic dimensions: M, L, T.

• Example:

  • Speed: LT⁻¹

  • Force: MLT⁻²

• Uses:

  • Check equation correctness

  • Derive relations

  • Find unit of unknown quantities

1.4 Measurement Instruments & Errors

Instruments:

• Vernier caliper, Screw gauge, Spherometer

• Triple-beam / Electronic balance

• Stopwatch

Errors:

• Systematic errors: Faulty apparatus, zero error

• Random errors: Skill limitations

• Least count: Minimum measurable value

• Absolute error, Fractional error, Percentage error

1.5 Vectors – Addition & Resolution

• Scalars: Only magnitude (mass, time)

• Vectors: Magnitude + direction (force, velocity)

Methods:

• Triangle law

• Parallelogram law

• Vector components:

  • Fx = F cosθ

  • Fy = F sinθ

1.6 Graphs in Physics

Graph types:

• Displacement–Time (s–t)

• Velocity–Time (v–t)

Key ideas:

• Slope of s–t graph = velocity

• Slope of v–t graph = acceleration

• Area under v–t graph = displacement

• Proper scaling, labeling, choice of axes

2. Detailed Notes for Each Section

2.1 Scientific Method

• Observation: Gathering data (e.g., apple falling).

• Hypothesis: Proposed explanation.

• Experiment: Testing the hypothesis.

• Theory: Verified explanation.

• Prediction: Using theory to forecast outcomes.

Applications of Physics

• GPS satellites (relativity)

• Medical scans (X-rays, MRI)

• Electronics (semiconductors)

• Renewable energy systems

2.2 Physical Quantities, Units & Prefixes

Base Quantities & Units

Derived Units Examples

• Speed → m/s

• Acceleration → m/s²

• Force → N (= kg·m/s²)

SI Prefixes

2.3 Dimensions

Examples

• Density: ML⁻³

• Pressure: ML⁻¹T⁻²

• Energy: ML²T⁻²

Dimensional Homogeneity

All terms in a valid equation must have the same dimensions.

Example check:

• u·t → LT⁻¹ × T = L

• a·t² → LT⁻² × T² = L✔ Equation is correct.

2.4 Measuring Instruments

Vernier Caliper

• Measures: Internal, external diameters & depth

• Least count: 0.01 cm typically

Screw Gauge

• Measures: Very small thicknesses

• Least count: pitch/no. of divisions

• Zero error must be corrected

Error Types

• Absolute error: ± least count

• Fractional: (error / measurement)

• Percentage: (error / measurement) × 100%

2.5 Vectors

Addition

• Triangle method: Tail-to-head

• Parallelogram method: Diagonal gives resultant

Resolution

Breaking a vector into perpendicular components.

Example:A 10 N force at 30°:

• Fx = 10 cos 30° = 8.66 N

• Fy = 10 sin 30° = 5 N

2.6 Graphical Interpretation

Important Rules

• Independent variable → x-axis

• Dependent variable → y-axis

• Choose simple scales (1, 2, 5, 10)

• At least 6 plotted points

• Use a smooth line or best-fit

Graphs & Meaning

• s–t graph slope = velocity

• v–t graph slope = acceleration

• Area under v–t = displacement

3. Formula Summary for Unit 1

• Fractional error = Δx / x

• Percentage error = (Δx / x) × 100%

• Components of a vector:

  • Fx = F cos θ

  • Fy = F sin θ

• Slope = rise/run

• Area under curve = physical quantity (depends on graph type)

4. Common Mistakes to Avoid

• Writing units incorrectly (e.g., "ms" instead of "m/s").

• Forgetting zero error corrections on screw gauge.

• Using inconsistent scales on graph axes.

• Mixing scalar & vector quantities.

5. Exam Tips

• Always show steps for dimensional analysis.

• Draw large, neat diagrams for instruments.

• Check whether quantities are vectors or scalars.

• Graphs must include title, axes, units, and scale.

• When reading Vernier/Screw gauge: read main scale first, then add Vernier/Screw reading.

6. Quick Revision Table