Units and Measurements | Class 11 Physics Formulas

Chapter 1 : Units and Measurements

formulas Physics, Formulas, Kinematics, Measurements, Units, Definitions

Introduction

Physics serves as the backbone of understanding the natural world. It explains the fundamental principles governing matter, energy, and their interactions. This article presents a complete overview of the essential formulas and definitions from Chapter 1 of physics, covering key concepts such as dimensional analysis, units of measurement, significant figures, and basic kinematic equations.

1. Dimensional Analysis

Definition:

Dimensional analysis is a method used to convert one set of units to another and to verify the consistency of equations by analyzing their dimensions.

• Key Dimensions:
• Length (L): Measure of distance.
• Mass (M): Measure of the amount of matter.
• Time (T): Measure of duration.

Formula:

The dimensions of velocity can be expressed as:

Velocity = [L][T]⁻¹

2. Units of Measurement

Definition:

Units of measurement provide a standard for quantifying physical quantities. The International System of Units (SI) is widely used in physics.

• SI Units:
• Length: Meter (m)
• Mass: Kilogram (kg)
• Time: Second (s)
• Electric Current: Ampere (A)
• Temperature: Kelvin (K)
• Amount of Substance: Mole (mol)
• Luminous Intensity: Candela (cd)

3. Conversion of Units

Definition:

Unit conversion is the process of converting a quantity from one unit to another, often necessary in calculations.

General Formula:

To convert units:

New Value = Old Value × Conversion Factor

Example:

Convert 10 meters to centimeters:

10 m = 10 × 100 = 1000 cm

4. Significant Figures

Definition:

Significant figures indicate the precision of a measurement. They are the digits in a number that carry meaningful information about its precision.

Rules for Determining Significant Figures:

• All non-zero digits are significant.
• Any zeros between significant digits are significant.
• Leading zeros are not significant.
• Trailing zeros in a decimal number are significant.

Example:

The number 0.00456 has three significant figures.

5. Basic Kinematic Equations

Definition:

Kinematics is the branch of mechanics that describes the motion of objects without considering the forces that cause the motion.

Key Kinematic Equations:

1. Equation 1: v = u + at
   Where:
   v = final velocity (m/s)
   u = initial velocity (m/s)
   a = acceleration (m/s²)
   t = time (s)
2. Equation 2: s = ut + ½at²
   Where:
   s = displacement (m)
3. Equation 3: v² = u² + 2as

6. Important Definitions

• Velocity: The rate of change of displacement with respect to time. It is a vector quantity and has both magnitude and direction.
• Acceleration: The rate of change of velocity with respect to time. It is also a vector quantity.
• Displacement: The change in position of an object. It is a vector quantity and is measured in meters (m).
• Distance: The total length of the path traveled by an object, regardless of direction. It is a scalar quantity.
• Mass: A measure of the amount of matter in an object, typically measured in kilograms (kg).
• Weight: The force exerted on an object due to gravity. It can be calculated using the formula: Weight = m · g
  Where:
  m = mass (kg)
  g = acceleration due to gravity (approximately 9.81 m/s² on Earth).