# Oscillations Notes, Class 11 Physics | SwaVid Oscillations, NCERT Class 11 Physics: notes with key ideas, formulas, common mistakes and 3 quick checks with worked answers. Canonical: https://www.swavid.com/cbse/class-11/physics/chapter/oscillations Source: https://www.swavid.com/cbse/class-11/physics/chapter/oscillations # Oscillations ## Formulas and definitions ## Key ideas ## Common mistakes ## Quick checks ## Keep going ## Questions parents ask ## Class 11 Physics on SwaVid ### Periodic and oscillatory motion ### Simple harmonic motion ### Displacement, velocity, and acceleration ### Energy in SHM ### Spring-block system ### Simple pendulum ### Next chapter ### Related chapter ### Related chapter ### All chapters SwaVid › CBSE › Class 11 › Physics › Oscillations Notes written by SwaVid from the NCERT textbook. Class 11 Physics, Chapter 13. Key ideas, formulas and common mistakes. CBSE prints 10 marks for Unit X together, not for this chapter alone. Short answer. This chapter explains periodic and oscillatory motion with a focus on simple harmonic motion. It derives relations for displacement, velocity, acceleration, energy, and time periods of springs and simple pendulums. Source: NCERT Physics Part II (Reprint 2026-27) , Chapter 13, Oscillations A motion that repeats itself at regular intervals of time is periodic. An oscillatory or vibratory motion is a to-and-fro periodic motion about a mean equilibrium position. Simple harmonic motion (SHM) is an oscillatory motion where the restoring force or acceleration is directly proportional to displacement and directed toward the mean position. The displacement is described by a single harmonic function of time. Displacement follows x(t) = A cos(ωt + φ). Velocity leads displacement by a phase of π/2, while acceleration leads displacement by a phase of π and is proportional to -ω²x. An oscillating particle exchanges kinetic energy and potential energy continuously. The total mechanical energy is constant and directly proportional to the square of the amplitude. A block of mass m attached to a massless spring of force constant k executes SHM when displaced. Its angular frequency depends only on the spring constant and the mass. A point mass suspended by a light inextensible string executes SHM for small angular displacements. Its time period depends only on the length of the string and acceleration due to gravity. Try each question first. Then tap it to see the answer. ω = 2π / T = 2π / 2 = π rad s⁻¹ a max = ω² A = π² × 0.05 Taking π² ≈ 9.87, a max = 9.87 × 0.05 = 0.4935 m s⁻² 0.4935 m s⁻² T = 2π √(m / k) = 2π √(2 / 200) T = 2π √(1 / 100) = 2π / 10 = π / 5 s T ≈ 3.1416 / 5 ≈ 0.628 s 0.628 s K = (1/2) k (A² - x²) and U = (1/2) k x² Setting K = U gives (1/2) k (A² - x²) = (1/2) k x² A² - x² = x² → 2x² = A² → x = ± A / √2 ± A / √2 Waves . Work, Energy and Power . Laws of Motion . The 14 chapters of Class 11 Physics . CBSE does not give marks to one chapter. It prints 10 marks for Unit X together (Oscillations and Waves). Oscillations is part of that group. No. They are written by SwaVid from the NCERT textbook. The CBSE curriculum is the reference for what is assessed. Waves. SwaVid is an AI tutor for Indian students in Classes 6 to 12. It finds the earlier ideas a child missed, then teaches today’s chapter. Start free to see how it works. - Ch 13 NCERT book - 10 marks, Unit X together - 3 quick checks - Treating all periodic motions as simple harmonic motions . Check if the restoring force is proportional to the displacement. A uniform circular motion or planetary orbit is periodic, but only a projection on a diameter is simple harmonic. - Using simple pendulum time period formula for large swing angles . The formula T = 2π √(L / g) holds only for small angular displacements where sin θ ≈ θ. For large angles, the motion is oscillatory but not simple harmonic. - Confusing maximum velocity with maximum acceleration positions . Velocity is maximum at the mean position (x = 0) where acceleration is zero. Acceleration is maximum at the extremes (x = ±A) where velocity is zero. - Believing time period of a simple pendulum depends on bob mass . Look at the formula T = 2π √(L / g). 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