Ch 10Oscillations — Class 11 Physics, concept-first.

Have you ever seen a Thanjavur dancing doll (in Tamil, 'Thanjavur thalayatti bommai'), a well-known Indian craft figure whose head and body, once disturbed, rock gently to and fro until the movement g…

Motion in physics is broadly classified as repetitive (periodic) or non-repetitive (non-periodic). Periodic motion is any motion that repeats itself after a fixed interval of time -- the hands of a pe…

When an object or particle moves back and forth repeatedly about some reference position for a period of time, its motion is called oscillatory or vibratory motion.

Simple Harmonic Motion (SHM) is a special, particularly important type of oscillatory motion in which the acceleration (or the net force) on the particle is always directly proportional to its displac…

A neat geometric way to picture SHM is as the shadow of uniform circular motion. Consider a particle moving with constant speed on the circumference of a circle of radius , centred at the origin, in t…

Let be the particle's position on the reference circle of radius at time ; its displacement from the mean position is .

The time period is the time taken to complete one full oscillation. Since one complete revolution on the reference circle corresponds to , setting gives , so .

When a rigid body is set free to rotate about a fixed axis and is displaced from its equilibrium orientation, it can undergo angular oscillation exactly analogous to linear SHM.

Since angular acceleration is , the torque equation becomes , which has exactly the form of the SHM differential equation .

Linear SHM and angular SHM are structurally identical, differing only in which physical quantities play the roles of displacement, inertia, and restoring constant.

A Linear Harmonic Oscillator is any system obeying Hooke's law, , written , where the negative sign shows the restoring force always opposes the displacement.

Consider a block of mass attached to one end of a massless spring of stiffness (force/spring) constant , the other end fixed, resting on a smooth (frictionless) horizontal surface.

Now hang a massless spring of stiffness constant from a rigid support (a ceiling), with natural (unloaded) length .

The spring (or stiffness) constant measures how stiff a spring is: a larger needs more force to stretch or compress the spring by a given amount, and a smaller means the spring stretches easily.

A simple pendulum is a point mass (bob) of mass hung from a fixed support by a light, inextensible string of length (measured to the bob's centre of gravity).

As a particle executes SHM, it continually exchanges energy between two forms -- kinetic energy (KE), associated with its speed, and potential energy (PE, or elastic PE for a spring), associated with…

Real oscillators can be grouped by how their energy behaves over time: an oscillator left entirely alone vibrates at its own natural frequency with constant amplitude (free oscillation); a real oscill…

When an oscillator is simply displaced from its equilibrium position and let go, with nothing further acting on it besides its own restoring force, it oscillates at a frequency equal to its own natura…

The free-oscillation picture assumes no energy loss, but real oscillators sit inside a real medium -- air, oil, or some structural material -- whose friction and drag continually remove energy from th…

Left to itself, a damped oscillator's amplitude keeps shrinking until it eventually stops -- a child on a swing, for instance, slows down after a few cycles purely because of damping, unless somebody…

An oscillator that is driven by an external periodic agency in order to overcome damping (rather than merely to compensate for the exact energy lost, as in maintained oscillation) is called a forced o…

Resonance is the special case of forced oscillation in which the frequency of the external periodic (driving) force exactly matches the natural frequency of the oscillator being driven.

This unit's core results, gathered for quick revision: Oscillatory motion is back-and-forth motion about a reference point; SHM is the special case where the restoring force/acceleration is proportion…

The unit's concept map traces a single chain: Oscillation specialises to Simple Harmonic Motion, defined by and the equation , with and .

The chapter-end evaluation is organised in four parts of increasing depth. Part I (Multiple Choice Questions) has 15 objective questions, several drawn from NEET/AIPMT/IIT-JEE/NSEP question banks, cov…

Sample papers and previous-year board questions for this subject.