Units & Dimensions Explained – CHEMASH (Physics 2026)
Units and Dimensions form the foundation of Physics. Every numerical problem, formula derivation, and concept in Physics starts with correct understanding of units and dimensions. At CHEMASH, we explain this topic in a simple, exam-oriented and problem-solving focused way for students of Class 6 to 12, JEE & NEET 2026.
Table of Contents
- What are Units?
- SI System of Units
- What are Dimensions?
- Dimensional Analysis
- Solved Numericals
- MCQs (Exam Oriented)
- FAQs
- Why CHEMASH?
1️⃣ What are Units?
A unit is a standard reference used to measure a physical quantity.
Example:
- Length → meter (m)
- Mass → kilogram (kg)
- Time → second (s)
Without units, numerical values have no physical meaning.
2️⃣ SI System of Units
| Physical Quantity | SI Unit | Symbol |
|---|---|---|
| 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 |
International System of Units (BIPM)
3️⃣ What are Dimensions?
Dimensions represent the powers of fundamental quantities involved in a physical quantity.
Example:
- Velocity = [L¹T⁻¹]
- Force = [MLT⁻²]
Dimensions help us understand relationships between physical quantities.
4️⃣ Dimensional Analysis
Dimensional analysis is used to:
- Check correctness of equations
- Derive formulas
- Convert units
Example:
Check: F = ma
Dimensions of RHS = [M][LT⁻²] = [MLT⁻²] ✔
5️⃣ Solved Numerical (2026 Exam)
Q: Find dimensional formula of Pressure.
Solution:
Pressure = Force / Area
= [MLT⁻²] / [L²]
= [ML⁻¹T⁻²]
MCQs (JEE / NEET / Boards)
1. Dimensional formula of Energy is:
A) [MLT⁻²] B) [ML²T⁻²] ✔ C) [ML⁻¹T⁻²] D) [M²LT⁻²]
Answer: B
Explanation: Energy = Work = Force × Distance
Frequently Asked Questions
Q1. Is Units & Dimensions important for exams?
Yes, it is one of the most scoring chapters in Physics.
Q2. Does CHEMASH cover numericals?
Yes, CHEMASH focuses heavily on numericals and problem solving.
Why Study Physics with CHEMASH?
- Low-budget tuition for all classes
- Experienced & friendly teachers
- Concept + numericals + exams focus
- Trusted by students & parents
- Classes for Class 6 to 12, JEE & NEET
CHEMASH believes:
समझ के पढ़ो, रटने के लिए नहीं Physics made easy, affordable & trusted
