Introduction
Ace Chapter 4, Work, Energy and Power (New Course 2026-2027), with HSA Notes super concise, exam-focused notes designed to help students aim for 90 plus marks in their Punjab Board exams. This page covers the definition of work, conservative and non-conservative forces, variable force calculations, and power, prepared strictly according to the PCTB/PECTAA New Course syllabus, along with fully solved MCQs, short questions, and numericals.
This chapter builds on the vector and force concepts from Chapter 2, introducing work as the dot product of force and displacement and connecting it to the broader concept of energy.
Work, Energy and Power is a heavily tested chapter across all Punjab Boards, and understanding when work is zero, positive, or negative is essential for handling both conceptual and numerical questions confidently.
Why HSA Notes?
- Super concise and exam-focused
- Key definitions highlighted
- All formulas boxed
- Easy solved MCQs, short questions, and numericals
- Conceptual clarity points
- Diagrams included
- Quick revision bullets
- Free PDF download
Exercises Solved
This chapter’s exercise solutions from HSA Notes cover every question type set across all Punjab Boards, with full working shown for each answer.
Solved MCQs
1. Is work a scalar quantity? Yes
2. Is work zero when the angle between force and displacement is 90°? Yes
Solved Short Questions
1. Define work.
Work is defined as the product of force and displacement in the direction of the applied force.
2. When is work done zero?
Work is zero when the applied force is zero, when the displacement is zero, or when the angle between force and displacement is 90°.
3. What is a conservative force?
A conservative force is one for which the work done is independent of the path taken between two points.
4. What is a non-conservative force?
A non-conservative force is one for which the work done depends on the specific path taken between two points.
5. How is work calculated for a variable force?
For a variable force, work done is equal to the area under the force-displacement (F-d) graph.
Solved Numerical Problems
1. A force F = 10 N acts over a displacement d = 5 m at θ = 0°. The work done is W = 50 J.
2. A person carries a load horizontally, where the applied force is vertical and displacement is horizontal (θ = 90°). The work done is W = 0.
3. For a satellite in a circular orbit, the gravitational force acts perpendicular to the direction of motion at every instant. The work done by gravity is W = 0.
4. A spring is stretched with maximum force F_max = 20 N over a distance x = 0.1 m. The work done is:
W = ½ × 20 × 0.1 = 1 J
5. A mass m = 10 kg is lifted to a height h = 4 m. The work done against gravity is:
W = mgh = 392 J
6. A force F = 50 N pushes an object through a displacement d = 10 m at θ = 60°. The work done is:
W = 50 × 10 × 0.5 = 250 J
7. A spring with spring constant k = 200 N/m is compressed by x = 0.05 m. The work done is:
W = ½kx² = 0.25 J
View the full PDF for complete diagrams, tables, and extra MCQs, shorts, numericals, and long questions.
Official Textbook Reference
Download the official PCTB Class 11 Physics textbook (New Course 2025-2026) directly from the Punjab Curriculum & Textbook Board.
Why This Chapter Matters
Work, Energy and Power introduces the principle of energy conservation, one of the most powerful and widely applied ideas in all of Physics.
Understanding exactly when work is zero, such as in circular orbits or when carrying a load horizontally, is a common source of conceptual exam questions, while spring-related numericals using W = ½kx² are frequently tested across all Punjab Boards.
The distinction between conservative and non-conservative forces introduced in this chapter also becomes essential again in later chapters involving fluid mechanics and real-world energy losses.
Available Across All Punjab Boards and Top Schools
These notes are built for students across all Punjab Boards, including BISE Lahore, Gujranwala, Multan, Faisalabad, Sargodha, Rawalpindi, Dera Ghazi Khan, Bahawalpur, and Sahiwal, and are used at top schools including Aitchison College, Lahore Grammar School, Beacon-house, The City School, LACAS, Convent of Jesus & Mary, DPS Lahore, Garrison Academy, Bloomfield Hall, and Sadiq Public School Bahawalpur.
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Frequently Asked Questions
When is work done equal to zero?
Work is zero when the applied force is zero, the displacement is zero, or when the force acts perpendicular to the displacement, as in the case of a satellite in circular orbit or carrying a load horizontally.
What is the difference between conservative and non-conservative forces?
A conservative force does work that is independent of the path taken, while a non-conservative force does work that depends on the specific path taken between two points.
How is work calculated for a spring?
Work done on or by a spring is calculated using W = ½kx², where k is the spring constant and x is the displacement from the natural length.
How do you calculate work done for a variable force?
Work done for a variable force is found by calculating the area under the force-displacement (F-d) graph.
Conclusion
With Chapter 4, Work, Energy and Power, fully covered, Class 11 students across all Punjab Boards now have a clear understanding of work, conservative and non-conservative forces, and how to handle both constant and variable force calculations, along with fully solved MCQs, short questions, and numericals. Practice these solved exercises alongside past papers, and consider joining our online classes for guided, exam-focused preparation, to build the accuracy and confidence needed for your board exam.
Best of luck for your Class 11 Physics exam!