CBSE Class 9 Physics Chapter 8 Force and Laws of Motion — 20 MCQs with Answers

Understanding when forces produce a change in motion is foundational. CBSE often asks students to identify whether a scenario involves balanced or unbalanced forces and predict the resultant effect. The net force, or resultant force, determines acceleration. When forces cancel out (net force = zero), motion remains unchanged; when they do not, acceleration occurs. These MCQs test your ability to apply this logic to everyday situations like a book on a table, a car braking, or a tug-of-war. Remember that balanced forces can act on both stationary objects and objects moving at constant velocity — this distinction often appears in CBSE MCQs.

Newton's First Law, also called the Law of Inertia, states that an object resists change in its state of motion. This law is tested through situational questions: passengers lurching forward when a bus brakes, a coin dropping into a glass when a card is flicked, or a satellite moving at constant speed in space. The key is recognising that inertia is mass-dependent — heavier objects resist change more. CBSE loves assertion-reason MCQs here, pairing a statement about inertia with a reason about mass or velocity. Always check whether the reason correctly explains the assertion. These four MCQs cover real-world inertia scenarios and the relationship between mass and inertia, as per NCERT.

Newton's Second Law is the quantitative heart of this chapter. CBSE asks both conceptual questions (what happens if mass doubles?) and numerical MCQs (calculate force or acceleration). The formula F = m × a implies that for a given force, acceleration is inversely proportional to mass, and for a given mass, acceleration is directly proportional to force. Typical MCQs involve calculating one variable when two are given, or predicting the effect of changing mass or force. Remember that the SI unit of force is the Newton (N), defined as 1 N = 1 kg·m/s². These MCQs include both direct application and reasoning about proportionality, exactly as seen in the 2024 CBSE board paper.

Newton's Third Law states that every action has an equal and opposite reaction. The trick is recognising that action and reaction forces act on different objects, so they never cancel. CBSE tests this through real scenarios: gun recoil, rocket propulsion, swimming, walking. Students often confuse action-reaction with balanced forces — balanced forces act on the same object, action-reaction on different objects. These MCQs require you to identify the correct action-reaction pair and avoid common misconceptions. For example, when you walk, you push the ground backward (action), and the ground pushes you forward (reaction). This is fundamental for understanding how forces enable motion.

Momentum (p = m × v) measures the quantity of motion. The Law of Conservation of Momentum is powerful: in an isolated system, total momentum before collision equals total momentum after. CBSE tests this through numerical MCQs involving two objects colliding or exploding. Common scenarios include toy trains colliding, a bullet fired from a gun (recoil), or a skater pushing another. The key is setting up the equation m₁u₁ + m₂u₂ = m₁v₁ + m₂v₂ correctly, paying attention to direction (positive/negative). Remember that momentum is a vector — direction matters. These MCQs require both conceptual understanding (why is momentum conserved?) and numerical problem-solving (calculate final velocities).

Chapter 8 is concept-heavy and formula-driven, making it ideal for AI-powered personalised practice. CBSETUTOR.ai offers unlimited MCQ practice on Force and Laws of Motion, with instant feedback on every answer. Simply snap a photo of any MCQ from your textbook or sample paper, and the AI tutor explains the solution step-by-step, highlighting exactly which concept (First Law, Second Law, momentum conservation) applies. The platform adapts to your progress — if you struggle with Newton's Third Law MCQs, it serves more targeted questions until you are confident. You can practice assertion-reason MCQs, numerical problems, and HOTS questions 24×7 from your phone. At a flat ₹999/month for every CBSE class (6–12), you get round-the-clock doubt-solving, unlimited chapter-wise tests, and detailed performance analytics. Start with a 3-day free trial and see how quickly your MCQ accuracy improves before the next term exam.

CBSE has introduced assertion-reason format MCQs in the 2025 board exam pattern. You are given two statements: Assertion (A) and Reason (R). You must determine if both are true, if R correctly explains A, or if one is false. This format tests deeper understanding. For example: Assertion: 'A cricket ball and a tennis ball fall at the same rate in vacuum.' Reason: 'Both have the same inertia.' Here, Assertion is true (no air resistance, so acceleration = g for both), but Reason is false (inertia depends on mass, which differs). So answer is 'A is true, R is false'. Practise these carefully — they carry the same marks as standard MCQs but require more thought. The key is checking both truth value and logical connection between A and R.

The 2025 CBSE Class 9 Physics paper allocates roughly 8–10 marks to MCQs (4–5 questions of 1–2 marks each). Speed and accuracy matter — you have about 1 minute per MCQ. First, read the question stem carefully, underlining key terms like 'balanced', 'unbalanced', 'action-reaction', or numerical values. Eliminate obviously wrong options immediately. For numerical MCQs, do a quick mental check of units and order of magnitude before calculating. If an option is dimensionally incorrect, cross it out. For assertion-reason MCQs, evaluate the assertion first: if it is false, you can eliminate options (A) and (B) instantly. If you are stuck, flag the question and move on — return to it after finishing easier sections. Never leave an MCQ unanswered; there is no negative marking in CBSE board exams, so an educated guess based on elimination is always better than a blank. Finally, use NCERT language in your mind — CBSE MCQs are often lifted directly from NCERT definitions and examples, so familiarity with the textbook wording gives you an edge.