SCIENCE IMPORTANT FORMULAE CLASS - 9
Important Formulae for class 9 science
Updated for new syllabus - 2026
Class 9 science Important Formulae
The Important Science Formulae section at Saraswat Academy provides a complete collection of chapter-wise scientific formulas based on the latest CBSE Syllabus 2026–27. These formulas are carefully selected from the NCERT textbooks and presented in a simple, easy-to-understand format for quick learning and revision. They help students strengthen their conceptual understanding, solve numerical problems accurately, and improve problem-solving speed in Physics, Chemistry, and other formula-based topics. Regular practice of these formulas is essential for homework, class tests, unit tests, practical examinations, half-yearly examinations, annual examinations, and CBSE board examinations. This page serves as a quick revision resource, enabling students to recall important formulas confidently and perform better in both school and competitive examinations.
Regular revision of scientific formulas helps students strengthen conceptual understanding, improve numerical problem-solving skills, and reduce errors in calculations during examinations. Whether you are preparing for school assessments, practical examinations, or CBSE board exams, these chapter-wise science formula sheets provide a quick and effective revision resource. Students are encouraged to practise these formulas alongside NCERT questions, exemplar problems, practical-based questions, competency-based questions, and previous years' board questions to develop scientific reasoning, enhance accuracy, and achieve excellent marks in Science.
Important Formulae: Science Class - 9
Chapter - 7
Important Formulae – Chapter 7: Work, Energy and Simple Machines
1. Work Done by a Constant Force
Formula
W = F × s
where
- W = Work done
- F = Force applied
- s = Displacement in the direction of force
2. SI Unit of Work
1 J = 1 N × 1 m
Also,
1 J = 1 kg m² s⁻²
3. Work-Energy Theorem
Work Done = Change in Energy
W = ΔE
4. Second Equation of Motion
v² = u² + 2as
Rearranged form:
s = (v² − u²)/(2a)
5. Newton's Second Law
F = ma
6. Work in Terms of Velocity
W = ½m(v² − u²)
7. Kinetic Energy
K = ½mv²
8. Gravitational Work
W = mgh
9. Gravitational Potential Energy
U = mgh
10. Mechanical Energy
Mechanical Energy = Kinetic Energy + Potential Energy
ME = K + U
11. Mechanical Energy at the Top
PE = mgh
KE = 0
ME = mgh
12. Velocity During Free Fall
v = gt
13. Height During Free Fall
h′ = h − ½gt²
14. Potential Energy During Free Fall
PE = mgh − ½mgt²
15. Kinetic Energy During Free Fall
KE = ½mgt²
16. Mechanical Energy During Free Fall
ME = mgh
(Mechanical energy remains constant if friction is neglected.)
17. Velocity from Conservation of Energy
mgh = ½mv²
Therefore,
v = √(2gh)
18. Power
Power = Work Done / Time
P = W/t
19. SI Unit of Power
1 W = 1 J/s
20. Mechanical Advantage (MA)
MA = Load / Effort
MA = L/E
21. Velocity Ratio (VR)
VR = Distance moved by Effort / Distance moved by Load
22. Efficiency
Efficiency = (Useful Work Output / Work Input) × 100%
or
Efficiency = (MA / VR) × 100%
Important SI Units
| Physical Quantity | SI Unit |
|---|---|
| Work | Joule (J) |
| Energy | Joule (J) |
| Kinetic Energy | Joule (J) |
| Potential Energy | Joule (J) |
| Mechanical Energy | Joule (J) |
| Power | Watt (W) |
| Force | Newton (N) |
| Distance | Metre (m) |
| Mass | Kilogram (kg) |
| Time | Second (s) |
Important Standard Values
- 1 J = 1 N × 1 m
- 1 J = 1 kg·m²/s²
- 1 W = 1 J/s
- g = 9.8 m/s² (approximately 10 m/s²)
- Mechanical Energy = Kinetic Energy + Potential Energy
- During free fall (ignoring friction), Mechanical Energy remains constant.
Quick Revision Formulae
- W = Fs
- W = ΔE
- F = ma
- v² = u² + 2as
- s = (v² − u²)/(2a)
- W = ½m(v² − u²)
- K = ½mv²
- U = mgh
- ME = K + U
- v = gt
- h′ = h − ½gt²
- v = √(2gh)
- P = W/t
- MA = L/E
- VR = Distance moved by Effort / Distance moved by Load
- Efficiency = (MA/VR) × 100%