Work and Energy — Class 9 Science MCQs
Practice 100+ MCQs on Work and Energy for Class 9.
Learn about Work, kinetic energy, potential energy, power and law of conservation of energy
with instant answers.
Quick Revision Box
- Scientific Work: Work is done only when a force causes displacement in its direction. W = F × s (in joules).
- Zero Work: No work is done if force is perpendicular to displacement or if there is no displacement.
- Energy: Capacity to do work. SI unit: joule (J).
- Kinetic Energy (KE): Energy due to motion. KE = ½ m v².
- Potential Energy (PE): Energy due to position or shape. Gravitational PE = m g h.
- Law of Conservation of Energy: Energy can neither be created nor destroyed; it only changes form.
- Mechanical Energy: Sum of KE and PE. Remains constant in an isolated system.
- Power: Rate of doing work. P = W/t. SI unit: watt (W).
- Commercial Unit of Energy: Kilowatt-hour (kWh). 1 kWh = 3.6 × 10⁶ J.
- Work-Energy Theorem: Work done on an object equals the change in its kinetic energy.
- Positive & Negative Work: Positive if force and displacement are in same direction; negative if opposite.
- Efficiency: Ratio of useful energy output to total energy input, often expressed as percentage.
Chapter Summary
Chapter 11: Work and Energy introduces the fundamental concepts that explain how forces cause changes in motion and how energy is transferred and transformed in physical systems. You'll move beyond everyday notions of “work” to understand its precise scientific definition—where work is done only when a force produces displacement. The chapter seamlessly connects work to energy, exploring its various forms like kinetic and potential energy, and establishes the powerful Law of Conservation of Energy, a cornerstone principle in physics.
What You Will Learn: This chapter builds your ability to calculate work done by constant and opposing forces, determine the kinetic energy of moving objects and the potential energy stored in raised objects or stretched springs, and apply the law of conservation of energy to solve problems involving falling bodies, pendulums, and simple machines. You'll also learn to calculate power—the rate of doing work—and understand commercial energy units like the kilowatt-hour, which links physics to real-life electricity consumption.
Exam-Oriented Importance: “Work and Energy” is a high-scoring chapter for Class 9 board exams (CBSE, ICSE, State Boards) and competitive tests like NTSE and Science Olympiads. It typically includes a mix of definition-based questions, derivation of formulas (like KE = ½ mv²), numerical problems on work, energy, and power, and application-based questions on energy conservation. Mastering this chapter allows you to tackle complex, multi-step problems confidently and solve questions efficiently under time pressure.
How This Website Helps: Our platform transforms your theoretical understanding into exam-ready skills. With a vast, graded repository of MCQs—from basic conceptual checks to challenging numerical problems—you can systematically test your grasp of every topic. Practicing these questions helps you quickly identify formulas, avoid common calculation traps, and apply the work-energy theorem and conservation principles accurately. This targeted, repetitive practice builds speed, boosts confidence, and ensures you can convert complex theory into guaranteed marks on your answer sheet.
Loading questions...