Class 9 Physics | Chapter 5 Work, Energy and Power | Numerical 5.12 | Power Developed by a Boy

Class 9 Physics | Chapter 5 Work, Energy and Power | Numerical 5.12 | Power Developed by a Boy Running Upstairs
In this lecture, we solve Numerical 5.12 from Chapter 5 “Work, Energy and Power” of Class 9 Physics (Punjab Textbook Board – New Syllabus 2025).
This numerical is based on the concept of power and work done against gravity. A boy runs upstairs to a certain height in a given time, and we calculate the power developed by him.
We use the formulas: 👉 Work Done (W) = mgh
👉 Power (P) = Work Done ÷ Time
📘 Given Data: Mass of boy = 40 kg
Height = 10 m
Time = 8 s
Acceleration due to gravity = 10 m/s²
First, we calculate the work done: 👉 W = 40 × 10 × 10 = 4000 J
Then we calculate power: 👉 P = 4000 ÷ 8
✅ Final Answer: Power = 500 W
🔎 What You Will Learn in This Video
Concept of power in physics
Work done against gravity
Use of formula �
Relation between work and power
Step-by-step numerical solving method
Board exam solving techniques
📚 Concepts Covered
✔ Power
✔ Work done
✔ Gravitational force
✔ Potential energy concept
✔ Formula �
✔ Formula �
✔ Watt as SI unit of power
✔ Scientific calculation method
🎯 Why Numerical 5.12 Is Important
Very important board exam numerical
Frequently asked in exams
Strengthens concepts of power and work
Improves calculation skills
Helpful for MCQs and theory concepts
Builds foundation for higher physics
👉 Watch full Chapter 5 Work, Energy and Power playlist for complete preparation.
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Видео Class 9 Physics | Chapter 5 Work, Energy and Power | Numerical 5.12 | Power Developed by a Boy канала Sir Bilal Saleem