Physics is a quantitative science. It explains natural phenomena using numbers, measurements, and mathematical relations. To describe the physical world accurately, we must measure quantities like length, mass, time, temperature, and speed using standardised units.
Measurement is the comparison of an unknown physical quantity with a known, universally accepted standard. A measurement always includes two parts:
- A numerical value
- A unit of measurement
Physical Quantities
A physical quantity is any property of a system that can be measured. There are two types:
- Fundamental quantities
- Derived quantities
Fundamental (Base) Quantities
These are independent and cannot be expressed in terms of other physical quantities. They include length, mass, time, temperature, electric current, amount of substance, and luminous intensity.
Derived Quantities
These are formed by combining fundamental quantities using mathematical operations. Examples include velocity, acceleration, force, momentum, density, pressure, and energy.
Why Measurement Is Necessary
Human senses help us make qualitative observations, but physics requires precise numerical information. For example, sight may tell us that one object is longer than another, but measurement tells us how much longer.
Accurate measurement allows us to:
- Compare physical quantities
- Form mathematical laws
- Perform scientific experiments
- Communicate results clearly across the world
Historical Need for Standard Units
Before standardisation, different regions used different units (like cubit, foot, handspan), leading to confusion. Modern science uses the SI system, which provides uniform units for global scientific communication.
Real-World Examples of Measurement
- Measuring the speed of a satellite in orbit
- Calculating the force needed to lift an object
- Recording the temperature of a chemical reaction
- Measuring distances in astronomy or microscopy
Understanding measurement is the first step in learning physics because it creates the framework for all subsequent laws, formulas, and concepts.
FAQs
Q1. What is the meaning of measurement in physics?
Measurement is the process of comparing an unknown quantity with a known standard unit to obtain a numerical value.
Q2. Why are physical quantities divided into fundamental and derived quantities?
Fundamental quantities are independent, while derived quantities are obtained from them using mathematical relationships. This classification helps organise physical concepts clearly.
Q3. Why can’t we rely only on our senses for measurement?
Human senses provide qualitative information, but physics requires precise, repeatable numerical data, which only standardized measurements can provide.
Q4. Why do different regions historically use different measurement units?
Before scientific standardisation, measurement systems evolved based on local practices, leading to inconsistency. Modern SI units eliminate this confusion.
Q5. Why is measurement essential for scientific laws?
Because scientific laws express relationships between numerical values of physical quantities, accurate measurement ensures reliability and universal validity.
Conclusion
The introduction to Units and Measurements provides the foundation for all scientific study in physics. Understanding the need for measurement, the types of physical quantities, and the evolution of standard units prepares students for deeper exploration of physical laws and quantitative reasoning.
At Deeksha Vedantu, students are encouraged to build strong fundamentals through clear conceptual explanations, real-world examples, and consistent practice-ensuring confidence in solving physics problems and excelling in competitive examinations.
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