Start of the session: Units and Measurements (11th standard)
Physics Overview
Definition: Branch of science dealing with the measurement of physical theories
Examples of physics in real life:
Light travel explanation (Physics)
Calculating sound speed (Physics)
Speed of a bike (Physics)
Units
Definition: Used to measure various types of physical quantities
Importance of correct units to avoid measurement errors
Example: Incorrect use of liters for gold measurement
Systems of Units
CGS: Centimeter, Gram, Second
MKS: Meter, Kilogram, Second
FPS: Foot, Pound, Second
SI (International System of Units): Global standard for measurements
Use of SI units for consistency across countries and fields
Example of SI unit adoption in exercise equipment (pounds in dumbbells)
Physical Quantities
Types: Fundamental and Derived
Fundamental Quantities: Not dependent on other physical quantities (e.g., Length, Mass, Time, Temperature, Electric Current, Luminous Intensity, Amount of Substance)
Derived Quantities: Dependent on other physical quantities (e.g., Velocity, Acceleration, Momentum)
Fundamental Quantities and SI Units
Length: Meter (m)
Mass: Kilogram (kg)
Time: Second (s)
Temperature: Kelvin (K)
Electric Current: Ampere (A)
Luminous Intensity: Candela (cd)
Amount of Substance: Mole (mol)
Derived Quantities Examples
Velocity: Meter per Second (m/s)
Acceleration: Meter per Second squared (m/s┬▓)
Momentum: Kilogram Meter per Second (kg┬╖m/s)
Example of dependency (Derived quantities like Velocity and Momentum are dependent on fundamental quantities)
Supplementary Units
Plane Angle: Radian (rad)
Solid Angle: Steradian (sr)
Plane Angle
Formula: \theta = ds / r
Use of radian as a unit
Solid Angle
Formula: \Omega = dA / r┬▓
Use of steradian as a unit
Conventions for Use of Units
Representation: Use symbols (N for Newton, m for meter)
Full Names: Always in lowercase (e.g., newton for Newton)
Combinations: Avoid mixing symbols and full names
Plural Form: Do not use plurals for units
Units in Ratios: Represent numerator and denominator units together
Dimensional Analysis
Uses: Check correctness of equations, find relations between quantities, convert between units
Example: Work = Force * Displacement
Dimensions: [M][L┬▓][T-┬▓] for Force; L for Displacement
Dimensional formula for Work: [M][L┬▓][T-┬▓]*
Measurement of Length
Methods for measuring large distances and small sizes
Parallax Method: Used for measuring large distances (e.g., between planets)
Parallax Method
Concept of apparent change in object position due to observer position change
Calculation of large distances using angles and physical observations
Measuring Small Sizes
Tools: Vernier Calipers, Screw Gauge for small dimensions
Quantum Scale: Advanced tools like tunneling microscope for minuscule particles like electrons
Errors in Measurements
Types of Errors
Systematic Errors: Consistent errors due to faulty instruments or techniques
Instrumental Error: Calibration issues
Imperfection in Experiment Technique: Incorrect usage technique by the operator
Personal Error: Observer's carelessness
Random Errors: Errors due to unexpected changes (temperature, voltage, etc.)
Both positive and negative possible
Measures of Error
Absolute Error: Difference between measured value and true value
Mean Absolute Error: Average of absolute errors from multiple readings
Relative Error: Mean absolute error divided by mean value
Percentage Error: Relative error multiplied by 100
Conclusion
Physics definition and its practical applications explained
Importance of units in measurement articulated
Systematic approach to understanding errors and their types emphasized