Physics: The Fundamental Science
Physics is the branch of science that deals with matter, energy and the relationship between them. The study of physics involves laws of motion, the structure of space and time, the nature and types of forces, the interaction between different particles, the interaction of radiation with matter etc.
Physics explores three main frontiers: the very large (universe), the very small (elementary particles), and the middle-sized (from molecules to Earth). This helps categorize different physics subfields.
Branches of Physics
Natural Philosophy to Modern Science
Initially, the observations of man about the world around him give birth to the single discipline of science, called natural philosophy. This later divided into physical sciences (non-living things) and biological sciences (living things).
Physical Quantities and Their Significance
The quantities that can be measured and are used to describe the properties of matter are called physical quantities. Also all those quantities in terms of which laws of physics can be described are called physical quantities.
Remember: “MaLT” for base quantities – Mass, Length, Time. These are the foundational quantities from which all others are derived.
Base vs Derived Quantities
Significance of Physical Quantities
The foundation of physics rest upon physical quantities in terms of which the laws of physics are expressed. For example; mass, length, time, velocity, force, density temperature, electric current etc. are the physical quantities.
International System of Units (SI)
In 1960, an international committee agreed on a set of definitions and standards to describe the physical quantities. The system that was established is called System International of units (SI).
Use the mnemonic: “My Tall Korean Mother Never Eats Instant Cereal” for Meter, Time, Kelvin, Mole, candela, Ampere, Kilogram (reordered for memorization).
SI Base Units
| Quantity | Symbol | SI Unit | Dimension |
|---|---|---|---|
| Length | L | meter (m) | [L] |
| Time | T | second (s) | [T] |
| Mass | M | kilogram (kg) | [M] |
| Temperature | T | kelvin (K) | [K] |
| Amount of Substance | N | mole (mol) | [N] |
| Electric Current | I | ampere (A) | [A] |
| Luminous Intensity | Iv | candela (Cd) | [J] |
Supplementary Units
These are dimensionless units used for angles:
- Radian (rad): Plane angle unit – angle between two radii of a circle corresponding to the arc length of one radius on its circumference.
- Steradian (sr): Solid angle unit – 3D angle subtended at the center of the sphere corresponding to the surface area of one square radius.
Derived Units
| Quantity | Symbol | SI Unit | In Base Units |
|---|---|---|---|
| Force | F | newton (N) | kg m s-2 |
| Work | W | joule (J) | kg m2 s-2 |
| Power | P | watt (W) | kg m2 s-3 |
| Pressure | P | pascal (Pa) | kg m-1 s-2 |
Measurement, Errors, and Significant Figures
Remember the rule: “Pacific to Atlantic” – If a decimal point is Present, start counting from the Pacific (left) side. If the decimal point is Absent, start counting from the Atlantic (right) side.
Errors in Measurement
The difference between the actual and calculated value of any measurement is called error.
Significant Figures Rules
- All non-zero digits (1-9) are significant
- Zeros between significant figures are significant (e.g., 1007 has 4 sig figs)
- Leading zeros are NOT significant (e.g., 0.00467 has 3 sig figs)
- Trailing zeros with a decimal point ARE significant (e.g., 7.4000 has 5 sig figs)
- In scientific notation, all digits before “× 10n” are significant
- 1007 = 4 significant figures
- 0.00467 = 3 significant figures
- 8.70 × 10-2 = 3 significant figures
- 8000 (with least count 10) = 3 significant figures
Precision vs Accuracy
Dimensional Analysis
How many times a physical quantity occurs in a given formula is called its dimension. To express any physical quantity by symbols of corresponding base quantities, written within the square brackets, is called its dimensional formula.
Use the homogeneity principle: For an equation to be physically correct, dimensions on both sides must be identical. This is a quick way to check equation validity.
Common Dimensional Formulas
- Velocity: [LT-1] (since v = d/t)
- Acceleration: [LT-2] (since a = v/t)
- Force: [MLT-2] (since F = ma)
- Work/Energy: [ML2T-2]
- Pressure: [ML-1T-2]
- Power: [ML2T-3]
Applications of Dimensional Analysis
Homogeneity Principle
According to homogeneity principle “If the dimensions of a physical quantity on both sides of equation are the same, then the equation will be dimensionally correct”.
Dimensions of v: [LT-1]
Dimensions of u: [LT-1]
Dimensions of at: [LT-2][T] = [LT-1]
All terms have same dimensions, so equation is dimensionally correct.
Effective Study Guidelines for Physics
Physics requires both conceptual understanding and problem-solving skills. Follow these guidelines to master the fundamentals:
- Understand Concepts First: Don’t just memorize formulas. Understand what each physical quantity represents and how they relate to each other.
- Master Units and Dimensions: Always include units in calculations and check dimensional consistency. This helps catch errors early.
- Practice with Real Examples: Apply concepts to everyday situations. For example, think about velocity when riding a bike or force when pushing objects.
- Use Visual Aids: Draw diagrams for problems involving motion, forces, or circuits. Visualization improves understanding.
- Solve Problems Systematically: Follow a step-by-step approach: 1) Identify knowns and unknowns, 2) Select appropriate formulas, 3) Substitute values with units, 4) Solve and check answer.
- Focus on Significant Figures: Pay attention to measurement precision. Your final answer should not have more significant figures than your least precise measurement.
- Learn Error Analysis: Understand how different types of errors affect measurements and how to minimize them in experiments.
- Connect Topics: See how different physics concepts interrelate. For example, how force relates to energy and work.
- Regular Revision: Physics builds on previous concepts. Regularly review earlier topics to maintain understanding.
- Use This Resource: Take the practice quiz to test your understanding. Review explanations for questions you get wrong.
When solving physics problems, allocate your time: 30% understanding the problem, 40% planning the solution, 20% calculation, and 10% checking your answer.
Physics Fundamentals Practice Quiz
Test your knowledge with 50 multiple-choice questions covering all topics. Select your answer and see immediate animated feedback!