CBSE Class 9 Physics Chapter 10 Work and Energy — 20 MCQs with Answers

Work in physics has a precise definition that often surprises students. It is done only when a force moves an object in the direction of the force. If displacement is zero or perpendicular to the applied force, work is zero regardless of how hard you push. These MCQs test whether you understand the vector nature of work, the role of the angle between force and displacement, and the formula W = F × d × cos(θ). They also check your ability to identify situations where no work is done despite obvious effort, such as carrying a load horizontally or holding a weight stationary. Mastering these questions builds a solid foundation for energy concepts that follow.

Kinetic energy (KE) is the energy of motion, calculated as ½mv². The quadratic dependence on velocity is critical: if you double the speed of a vehicle, its kinetic energy becomes four times larger. This explains why high-speed accidents are far more destructive. These MCQs test your ability to substitute values into the formula, compare kinetic energies of objects with different masses and speeds, and understand that kinetic energy is always non-negative and scalar. You will also see questions on how kinetic energy changes when velocity or mass is altered, a favourite topic in CBSE papers for testing proportional reasoning.

Potential energy is stored energy due to position or state. Gravitational potential energy PE = mgh measures energy stored when an object is raised above a reference level. The choice of reference (ground, table, floor) affects the absolute value but not the change in PE. Elastic potential energy is stored in springs, rubber bands, and stretched wires. These MCQs check your understanding of the mgh formula, the concept of a reference point, and how potential energy converts to kinetic energy during free fall. Questions also test whether you can identify situations where potential energy increases or decreases, and the effect of changing height, mass, or gravitational field strength.

The Law of Conservation of Energy is a foundation of physics. It states that in an isolated system, total energy remains constant; energy only transforms from one form to another. When a ball falls, gravitational PE decreases while KE increases by the same amount. At any instant, PE + KE = constant. These MCQs test your grasp of energy transformations in pendulums, free-falling objects, roller coasters, and hydroelectric plants. You must identify which forms of energy are involved, predict how energy splits between KE and PE at different points, and recognise that in real situations, some energy converts to heat and sound due to friction and air resistance.

Power measures how fast work is done or energy is transferred. The formula P = W/t (power = work/time) shows that the same work done in less time requires more power. A 60 W bulb consumes 60 joules of electrical energy every second. For household electricity, we use the kilowatt-hour (kWh) because joules are too small. One kWh is the energy consumed by a 1000 W (1 kW) appliance in one hour, equal to 3.6 million joules. These MCQs test unit conversions, calculation of power from work and time, understanding of watt and kilowatt ratings, and real-life applications like electricity bills and motor ratings.

MCQs in CBSE Class 9 Physics reward speed and accuracy. Start by reading the question stem carefully and identifying the key physical quantity asked—work, energy, power, or a transformation. Eliminate obviously incorrect options first; often one or two choices contradict basic definitions or units. For numerical MCQs, quickly jot down the formula, substitute values, and check units. If two options are close, re-check your calculation or reasoning. For assertion-reason questions, evaluate the assertion independently, then the reason, and finally check if the reason correctly explains the assertion. Do not spend more than 45 seconds per MCQ on first attempt; mark tricky ones and return later. Practice 10-15 MCQs daily from NCERT exemplar and previous years' papers to build speed. CBSETUTOR.ai offers unlimited chapter-wise MCQ quizzes for Class 9 Physics with instant AI feedback and step-by-step solutions. Upload your doubt via photo, get personalised explanations, and track your progress—all at a flat ₹999 per month across Classes 6-12, with a 3-day free trial to start.