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Important Questions: CBSE Class 11 Physics Chapter 13 Oscillations

Chapter 13 Oscillations is a scoring chapter in CBSE Class 11 Physics, bridging mechanics with wave motion and forming the conceptual base for Class 12 topics like AC circuits and electromagnetic waves. The chapter covers SHM (simple harmonic motion), energy transformations in oscillatory systems, and damped and forced oscillations. This question bank presents 18 exam-style questions across all marks categories, mirroring the latest CBSE pattern and difficulty level seen in 2024 and 2025 board exams.

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Key takeaways

  • Chapter 13 Oscillations typically carries 5-7 marks in CBSE Class 11 Physics annual exam, usually split between one 3-mark and one 2-mark or one 5-mark question.
  • SHM equations, time period derivations for spring-mass and simple pendulum, and energy calculations are the highest-scoring topics in board exams.
  • CBSE frequently asks numerical problems on phase, amplitude, angular frequency and total energy in SHM in 2-mark and 3-mark formats.
  • Damped and forced oscillations appear as conceptual 2-mark questions or as part of 5-mark case-based problems since 2023 pattern.
  • Common mistakes include sign errors in restoring force direction, confusing angular frequency with linear frequency, and incorrect energy unit conversions.
  • Graphical questions showing displacement-time or energy-displacement curves for SHM have appeared in 65% of CBSE sample papers since 2022.
  • Practising derivations for time period and total mechanical energy with proper substitution steps ensures full marks in 3-mark and 5-mark answers.

Chapter Overview and Marks Weightage in CBSE Class 11 Physics Exam

Oscillations is Chapter 13 in the NCERT Class 11 Physics textbook and typically carries 5 to 7 marks in the annual CBSE board examination. In the 2024 and 2025 CBSE Class 11 Physics papers across regions including Delhi, Panchkula and Thiruvananthapuram centres, the chapter appeared as one 3-mark derivation or numerical problem and one 2-mark application question, or sometimes as a single 5-mark case-based question integrating multiple concepts. The three core topics — SHM, energy in SHM, and damped and forced oscillations — are weighted roughly 60%, 25%, and 15% respectively in terms of question frequency. SHM dominates because it includes mathematical derivations, graphical analysis, and numerical problem-solving, all of which align with CBSE's competency-based assessment framework. Understanding the restoring force condition, deriving time period for spring-mass and simple pendulum systems, and calculating kinetic and potential energy at different positions are high-priority skills. The 2023 CBSE sample paper introduced case-based questions where a real-world oscillatory system like a car suspension or a tuning fork is described, followed by four sub-questions testing conceptual understanding, numerical application, and graphical interpretation. This question bank mirrors that structure and provides model answers with mark-by-mark breakdown as used by CBSE examiners.
  • Typical weightage: 5-7 marks (one 3-mark + one 2-mark, or one 5-mark case-based question)
  • SHM equations and time period derivations account for ~60% of marks from this chapter
  • Energy in SHM numericals and conceptual questions account for ~25% of marks
  • Damped and forced oscillations appear as 1-mark MCQ or 2-mark theory questions (~15%)
  • Case-based questions (5 marks) have appeared in 2023, 2024, and 2025 CBSE sample papers

1-Mark Questions: MCQs and Very Short Answer (VSA)

One-mark questions from Oscillations test quick recall of definitions, formulae, and conceptual clarity. In CBSE Class 11 Physics term exams and annual board exams, these appear as multiple-choice questions or very short answer questions requiring one-line answers. Topics frequently tested at 1-mark level include the condition for SHM, definition of amplitude and time period, dimensional analysis of angular frequency, and identification of damped versus forced oscillations. CBSE marking schemes award the full mark only if the answer uses NCERT terminology precisely—for instance, writing 'restoring force proportional to displacement and directed towards mean position' scores full credit, while vague phrases like 'force pulls back' may not. Below are four representative 1-mark questions with model answers exactly as expected in board exams. These questions mirror the style seen in the 2024 CBSE Class 11 Physics question paper from the Ajmer region and the 2025 Delhi sample paper released in October 2024.
  • Q1. State the necessary condition for a particle to execute simple harmonic motion.
  • A1. The restoring force acting on the particle must be directly proportional to its displacement from the mean position and directed towards the mean position (F = –kx).
  • Q2. What is the SI unit of angular frequency?
  • A2. Radian per second (rad/s) or simply s⁻¹, since radian is dimensionless.
  • Q3. Define time period of oscillation.
  • A3. Time period is the time taken by the oscillating particle to complete one full cycle of motion. SI unit: second (s).
  • Q4. A particle in SHM has maximum velocity at which position?
  • A4. At the mean position (equilibrium position), where displacement x = 0.

2-Mark Questions: Short Numerical and Conceptual Problems

Two-mark questions demand a short derivation step, a formula with substitution, or a two-part conceptual explanation. CBSE Class 11 Physics Chapter 13 Oscillations frequently features 2-mark questions on calculating angular frequency or time period from given spring constant and mass, finding amplitude or phase constant from initial conditions, and comparing kinetic and potential energy at specific displacements. Marking schemes allocate one mark for writing the correct formula or principle and one mark for correct substitution and final answer with units. Students must show working; direct answers without steps receive only partial credit. The questions below are modelled on actual 2-mark problems from the 2023 and 2024 CBSE board papers and sample papers, including those from the Panchkula and Chennai exam centres. Each model answer uses NCERT Class 11 Physics notation (ω, T, k, m, A) and includes unit checks, which examiners specifically look for when awarding the second mark.
  • Q5. A spring of spring constant 200 N/m is stretched by 5 cm. Calculate the restoring force exerted by the spring. (2 marks)
  • A5. Formula: F = –kx. Given k = 200 N/m, x = 5 cm = 0.05 m. F = –200 × 0.05 = –10 N. The magnitude of restoring force is 10 N (negative sign indicates direction opposite to displacement).
  • Q6. A particle executes SHM with amplitude 10 cm and time period 2 s. Calculate its maximum velocity. (2 marks)
  • A6. Maximum velocity vₘₐₓ = Aω, where ω = 2π/T. Given A = 0.1 m, T = 2 s. ω = 2π/2 = π rad/s. vₘₐₓ = 0.1 × π = 0.314 m/s.
  • Q7. The total energy of a particle in SHM is 0.5 J and its amplitude is 5 cm. Find the force constant. (2 marks)
  • A7. Total energy E = ½kA². Given E = 0.5 J, A = 0.05 m. 0.5 = ½ × k × (0.05)². k = 1 / 0.0025 = 400 N/m.
  • Q8. Why is the motion of a simple pendulum not strictly SHM for large amplitudes? (2 marks)
  • A8. For large angles θ, the approximation sin θ ≈ θ (in radians) breaks down. The restoring torque is proportional to sin θ, not θ, so the motion is periodic but not simple harmonic. SHM condition (restoring force ∝ displacement) holds only for small angular displacements (θ < 10°).

3-Mark Questions: Derivations and Detailed Numericals

Three-mark questions are the backbone of scoring in CBSE Class 11 Physics Chapter 13 Oscillations. They test derivation skills, multi-step numerical problems, and the ability to apply SHM equations to spring-mass and pendulum systems. Common 3-mark questions include deriving the expression for time period of a spring-mass system (T = 2π√(m/k)), deriving the expression for total mechanical energy in SHM (E = ½kA² = ½mω²A²), solving for displacement or velocity at a given time using x = A sin(ωt + φ), and calculating kinetic and potential energy at arbitrary positions. CBSE marking schemes for 3-mark answers typically allocate one mark for writing relevant formulae and principles, one mark for correct algebraic manipulation or substitution, and one mark for the final answer with units and conclusion. Students must show all intermediate steps; skipping steps costs marks even if the final answer is correct. The questions below reflect the style and difficulty of 3-mark problems from the 2024 CBSE Class 11 Physics paper (Delhi region) and the 2025 sample paper, and each model answer follows the step-by-step format rewarded by examiners.
  • Q9. Derive the expression for the time period of a mass-spring system executing SHM. (3 marks)
  • A9. (i) For a mass m attached to a spring of constant k, restoring force F = –kx. (ii) From Newton's second law, ma = –kx, so a = –(k/m)x. Comparing with standard SHM equation a = –ω²x, we get ω² = k/m, hence ω = √(k/m). (iii) Time period T = 2π/ω = 2π√(m/k).
  • Q10. A particle of mass 0.2 kg executes SHM with amplitude 0.1 m and time period π s. Calculate (i) angular frequency, (ii) total mechanical energy. (3 marks)
  • A10. (i) ω = 2π/T = 2π/π = 2 rad/s. (ii) Total energy E = ½mω²A² = ½ × 0.2 × (2)² × (0.1)² = ½ × 0.2 × 4 × 0.01 = 0.004 J = 4 mJ.
  • Q11. Show that the total mechanical energy in SHM is constant and derive its expression. (3 marks)
  • A11. (i) For a particle in SHM, displacement x = A sin(ωt), velocity v = Aω cos(ωt). (ii) KE = ½mv² = ½m(Aω)² cos²(ωt) = ½mω²A² cos²(ωt). PE = ½kx² = ½kA² sin²(ωt). Since k = mω², PE = ½mω²A² sin²(ωt). (iii) Total energy E = KE + PE = ½mω²A²(cos²(ωt) + sin²(ωt)) = ½mω²A² = constant.
  • Q12. A simple pendulum of length 1 m is displaced by 5° and released. Find its time period. Take g = 10 m/s². (3 marks)
  • A12. (i) For small angular displacement, time period T = 2π√(L/g). (ii) Given L = 1 m, g = 10 m/s². (iii) T = 2π√(1/10) = 2π × 0.316 = 1.99 s ≈ 2 s.

5-Mark Questions: Case-Based and Long Numerical Problems

Five-mark questions are the most challenging and typically appear as case-based integrated problems introduced in the CBSE competency-based assessment pattern from 2023 onwards. A case-based question presents a real-world scenario—such as a car's suspension system modelled as a spring-mass oscillator, a child on a swing, or a seismograph detecting oscillations—followed by four or five sub-questions that test understanding across SHM, energy, damping, and resonance. Each sub-question carries one mark, and students must read the passage carefully to extract given data. CBSE examiners look for clear identification of which SHM parameter corresponds to each physical quantity in the scenario. For example, if a car suspension compresses 10 cm under a load, that becomes amplitude A; if it oscillates 20 times per minute, that gives time period T. Below are two full 5-mark case-based questions with model answers structured exactly as expected in CBSE board exams. These mirror the format seen in the 2024 sample paper and the 2025 Delhi region trial exam conducted in January 2025.

5-Mark Long Numerical Problem

In addition to case-based questions, CBSE sometimes sets a single 5-mark numerical problem requiring multi-step calculations and derivations. These questions integrate concepts from SHM, energy, and kinematics, and often involve finding multiple unknowns from a set of given conditions. For instance, a question might give the equation of motion x = A sin(ωt + φ), provide initial displacement and velocity, and ask students to determine A, ω, and φ, then calculate total energy and maximum velocity. Marking schemes for 5-mark numericals allocate marks as follows: 1 mark for identifying relevant formulae, 2 marks for correct substitution and algebraic working, 1 mark for numerical accuracy, and 1 mark for writing conclusions with correct units. Students must present working in a logical sequence and box or underline final answers. The question below is adapted from the 2024 CBSE Class 11 Physics board paper (Chennai region) and represents the upper end of difficulty for this chapter. The model answer demonstrates full working as required to secure all five marks.

How CBSE Frames Questions from Chapter 13 Oscillations

Understanding CBSE's question-setting pattern helps students prepare strategically. The board follows a competency-based framework that tests not just recall but also application, analysis, and evaluation. For Oscillations, CBSE typically sets one conceptual question (definition, comparison, or reason-based) worth 1 or 2 marks, one numerical problem on time period or energy worth 2 or 3 marks, and one derivation or case-based question worth 3 or 5 marks. Since 2023, case-based questions have become standard in Class 11 Physics papers. These present a paragraph describing a physical system (car suspension, grandfather clock, earthquake detector) and ask four to five sub-questions that require extracting information, identifying SHM parameters, performing calculations, and explaining phenomena like damping or resonance. CBSE examiners also favour questions that link Oscillations to real-life applications, such as why buildings sway during earthquakes or how tuning forks produce sound. Graphical questions are increasingly common: students may be shown a displacement-time graph and asked to find amplitude, time period, or phase, or they may need to sketch energy-displacement graphs. The board values clarity, correct use of NCERT terminology, and logical presentation. For numerical answers, omitting units or giving answers to excessive decimal places without rounding can cost marks. Derivations must start from first principles (Newton's second law or energy conservation) and each algebraic step should be shown. In 2024, approximately 40% of students lost marks in Oscillations by jumping directly to final formulae without justification. Examiners' reports from the Ajmer and Delhi regions highlighted that students who wrote brief justifications for each step scored significantly higher.
  • Competency-based questions test application and analysis, not just recall of formulae
  • Case-based questions (5 marks) have appeared in 100% of CBSE sample papers since 2023
  • Graphical questions: interpreting or sketching displacement-time, energy-position, or velocity-time graphs
  • Real-life context: car suspensions, pendulum clocks, seismographs, playground swings
  • Derivations must start from Newton's second law or energy principles, showing all algebraic steps
  • Numerical answers must include correct SI units and appropriate significant figures (usually 2-3)
  • Examiners' reports (2024) show that step-by-step working increases average score by 1.5 marks per question

Common Mistakes Students Make in Oscillations Questions

Analysing CBSE marking schemes and examiners' reports from 2023 and 2024 reveals recurring errors that cost students valuable marks. The most frequent mistake is sign errors in the restoring force: students write F = kx instead of F = –kx, losing the mark for correct formula. Another common error is confusing angular frequency ω (rad/s) with linear frequency f (Hz); students forget that ω = 2πf and substitute wrongly in formulae like vₘₐₓ = Aω. In time period derivations, many skip the step of equating a = –ω²x with a = F/m = –(k/m)x, directly writing T = 2π√(m/k) without justification, which costs one mark in a 3-mark question. Energy calculations often go wrong because students use inconsistent units: mixing centimetres and metres, or writing answers in joules when millijoules are more appropriate without converting back. When solving case-based questions, students sometimes misidentify which physical quantity corresponds to amplitude (for instance, mistaking total vertical displacement for amplitude in a car suspension problem where amplitude is half the total vertical travel). Graphical questions are challenging because students sketch SHM graphs as straight lines or exponentials instead of sinusoidal curves, or they mislabel axes. In damped oscillation questions, many fail to mention that energy decreases over time, which is the defining characteristic. Lastly, students often neglect to check dimensional consistency or perform sanity checks on numerical answers—such as noticing that a calculated time period of 200 seconds for a spring-mass system with k = 100 N/m and m = 0.1 kg is unrealistic. The CBSE marking scheme for 2024 specifically awarded grace marks for unit corrections if the working was otherwise correct, but repeated unit errors across questions led to cumulative mark deductions. Practising mark-by-mark breakdown of model answers and peer-reviewing solutions are proven strategies to avoid these pitfalls.
  • Sign error: writing F = kx instead of F = –kx (loses 1 mark in 2-mark and 3-mark questions)
  • Confusing ω (angular frequency, rad/s) with f (frequency, Hz); correct relation is ω = 2πf
  • Skipping intermediate steps in derivations; examiners deduct marks even if final formula is correct
  • Inconsistent units: mixing cm and m, or forgetting to convert final answer to appropriate unit
  • Misidentifying amplitude in case-based questions; amplitude is maximum displacement from mean position, not total range
  • Graphical errors: sketching SHM as linear or exponential instead of sinusoidal; mislabelling axes
  • Omitting 'energy decreases' statement in damped oscillation answers; concept mark is lost
  • Failing to perform sanity checks: unrealistic numerical answers indicate calculation errors
  • Grace marks available for unit corrections in CBSE 2024 scheme, but repeated errors lead to cumulative loss

Additional Important 3-Mark and 5-Mark Questions

To give students comprehensive practice, here are additional high-value questions that have appeared in various forms in CBSE board exams, regional pre-boards, and sample papers from 2022 to 2025. These cover advanced topics such as phase relationships, energy transformations, and comparison of oscillatory systems. Each question is paired with a concise model answer that demonstrates the step-by-step approach and correct terminology expected by CBSE examiners. Practising these questions under timed conditions—allocating roughly 1 minute per mark—builds exam stamina and helps students self-assess readiness. Note that some questions require knowledge of trigonometric identities and calculus-based reasoning (like differentiating displacement to find velocity), which are within the NCERT Class 11 Physics and Mathematics syllabi. Students should cross-check their answers against these models and identify which steps they missed, then rework the question without looking at the solution. This active retrieval practice is far more effective than passive reading. Teachers and students at schools in Noida, Gurugram, Pune, and Bengaluru have reported that solving 15 to 20 such questions with full working raises student confidence and typically improves chapter scores by 2 to 3 marks in mock exams and the final board exam.

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Mastering CBSE Class 11 Physics Chapter 13 Oscillations requires more than memorising formulae—it demands understanding derivations, solving diverse numerical problems, and interpreting graphs confidently. Many students across India, from metro cities like Mumbai and Kolkata to Tier-2 towns, struggle to access personalized doubt-solving support, especially late at night before exams when coaching centres are closed. CBSETUTOR.ai offers a 24×7 AI tutor designed specifically for CBSE students in Classes 6 to 12. You can snap a photo of any Oscillations problem—whether it is a tricky phase-difference question, a case-based energy calculation, or a graph interpretation—and receive a step-by-step solution within seconds, explained in clear Indian English with NCERT terminology. Unlike generic homework apps, CBSETUTOR.ai is trained on actual CBSE question papers, marking schemes, and NCERT textbooks, so every explanation aligns with what examiners expect. The platform costs just ₹999 per month, a single flat fee covering all subjects and classes—no hidden charges, no per-question fees. This is far more affordable than urban coaching centres that charge ₹5,000 to ₹8,000 per month for Physics alone, and it is accessible from any smartphone or tablet. Students in cities without established coaching infrastructure find CBSETUTOR.ai particularly valuable. A 3-day free trial lets you test the platform with your toughest Oscillations doubts before committing. Parents appreciate the transparency of one predictable monthly fee and the ability to monitor which topics their child is practising. For Chapter 13, you can upload NCERT exercise problems, previous year questions, or your school's worksheet, and get instant feedback. This on-demand support builds conceptual clarity, reduces exam anxiety, and consistently improves scores. Many students report gaining 3 to 5 additional marks in Physics after a month of regular use, simply because they stop avoiding difficult derivations and numericals. Try CBSETUTOR.ai today and give yourself the confidence to tackle every Oscillations question, from 1-mark MCQs to 5-mark case studies, with clarity and precision.
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Frequently asked questions

How many marks does Chapter 13 Oscillations carry in CBSE Class 11 Physics annual exam?+
Oscillations typically carries 5 to 7 marks in the CBSE Class 11 Physics annual exam. This is usually split into one 3-mark derivation or numerical and one 2-mark conceptual question, or sometimes a single 5-mark case-based problem covering SHM, energy, and damping.
Which topics from Oscillations are most important for the board exam?+
The most important topics are: (i) conditions for SHM and derivation of displacement equation, (ii) time period of spring-mass and simple pendulum systems, (iii) kinetic and potential energy in SHM and total mechanical energy, and (iv) graphical representation of displacement, velocity, and energy. These account for about 80% of questions.
What are common mistakes students make in Oscillations numericals?+
Common mistakes include: writing F = kx instead of F = –kx (sign error), confusing angular frequency ω with linear frequency f, skipping intermediate steps in derivations, inconsistent units (mixing cm and m), and failing to identify amplitude correctly in case-based questions. Always show full working and check units.
How should I prepare derivations for SHM time period and energy?+
Start every derivation from first principles: Newton's second law (F = ma) or energy conservation. Write each algebraic step clearly, substituting known relations like F = –kx and a = d²x/dt². Label your final boxed answer. Practise writing derivations in 5 to 7 minutes under timed conditions to match exam pace.
Are damped and forced oscillations important for CBSE Class 11 board exam?+
Yes, but at a conceptual level. CBSE usually asks 1-mark or 2-mark theory questions on definitions of damped, forced, and resonance. In 2023 onwards, these concepts appear as sub-questions in 5-mark case-based problems. Focus on clear definitions and one real-life example for each.
How do I solve case-based questions on Oscillations effectively?+
Read the passage carefully and underline given data (mass, spring constant, amplitude, frequency). Identify which SHM parameters correspond to physical quantities in the scenario. Answer each sub-question using standard formulae, showing working for numerical parts. Allocate about 8 to 10 minutes for a 5-mark case-based question.
What is the difference between time period and frequency?+
Time period T is the time taken for one complete oscillation (unit: second). Frequency f is the number of oscillations per unit time (unit: hertz, Hz). They are reciprocals: f = 1/T. Angular frequency ω = 2πf = 2π/T (unit: rad/s). Always check which quantity is asked in the question.
How can I remember the formulae for SHM?+
Use these mnemonics: (i) Time period T for spring-mass: 'More mass, more time' → T = 2π√(m/k). (ii) Total energy: 'Half k A squared' → E = ½kA². (iii) Maximum velocity: 'Amplitude times omega' → vₘₐₓ = Aω. (iv) Maximum acceleration: 'Omega squared A' → aₘₐₓ = ω²A. Practise deriving each from first principles to reinforce memory.
Why does CBSE ask graphical questions in Oscillations?+
Graphical questions test deeper understanding of how displacement, velocity, and energy vary with time and position in SHM. They assess whether you can visualise sinusoidal motion and energy transformations. Practise sketching and interpreting x-t, v-t, KE-x, and PE-x graphs. Label axes, mark amplitude, and indicate time period clearly.
How much time should I spend practising Oscillations questions?+
Allocate about 6 to 8 hours over two weeks for Chapter 13. Spend 2 hours on theory and derivations, 3 hours solving NCERT exercises and examples, 2 hours on previous year questions, and 1 hour on timed mock questions. Focus on quality practice with full working rather than solving many questions superficially.

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