FSc ICS Notes Physics XI Short Questions & Definitions Chapter 7 Oscillations 1st Year Physics Notes Online Taleem Ilm Hub
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Translatory motion (or Rectilinear motion): A body moves
with translational motion if each particle of the body undergoes the same displacement in a straight line in a given time.
Rotatory motion: A body moves with rotational motion if each particle of the body moves in a circle about a straight line called the axis of rotation.
Vibratory motion (or Oscillatory motion): i) To and fro motion of a body about its mean position. ii) If the motion is back and forth over the same path about a mean position, it is called vibratory or oscillatory motion.
Periodic motion: A motion which repeats itself in equal intervals of time.
Periodic: Pertaining to a definite round of time; occurring or reoccurring at definite intervals.
Bob: A weight, e.g. a cork or small metallic mass, as on a pendulum.
Clamp: Anything that fastens, e.g. a piece of metal used to bring two corks together.
Skyscraper: A very tall building.
Elasticity: The property of a material body to regain its original condition, on the removal of the deforming forces.
Stress: The distorting force per unit area set up inside the body.
Strain: The change produced in the dimensions of a body under a system of forces.
Hook’s Law: Within the limits of perfect elasticity stress is directly proportional to strain.
Hooke’s law (modified form): Applied force on a body is directly proportional to the displacement.
As stress ∝ strain
F/A ∝ l /Lo
F ∝ (A/Lo ) l
F ∝ l [
A & Lo being constant ]
F ∝ x
F = k
x
Simple Harmonic Motion: i) The projection of uniform
circular motion upon any diameter of a circle. ii) A particle is said to posses a simple harmonic motion
if its acceleration is always directed towards the centre and its value is proportional to the displacement of the
particle from its central position.
Mean position: In to and fro motion, the central position around which a body moves.
Displacement: Distance from the equilibrium position at certain instant.
Instantaneous displacement: In a vibrating body, the value of its distance from the mean position at any instant of time.
Amplitude: The maximum distance traveled by a vibrating particle from its mean position.
Vibration: One complete round trip of the body.
Time period: It is the time required to complete one vibration.
Frequency: It is the number of vibrations executed by a body in one second.
Angular frequency: The number of complete rotations per unit time.
Sinusoidal waveform: Wave shape made like sine wave or like a curve plot of the function. y = sin θ.
Circular motion: A form of periodic motion, that of an object moving at constant speed in a circle of constant radius.
Trigonometry: The study of triangles, and various relations of sides and angles of triangles.
Algebra: That branch of mathematics which uses letters and other symbols instead of actual numbers and quantities for calculations.
Arithmetic: The branch of mathematics in which we use figures for calculations.
Trigonometric functions: Relations between the angle and sides of a right angled triangle, such as, sinθ, cosθ.
Sine θ: In right angled triangle, sine θ is equal to the opposite side divided by hypotenuse.
Cosine θ: In right angled triangle, cosine θ is equal to the base divided by hypotenuse.
Tangent θ: In right angled triangle, tangent θ is equal to opposite side divided by the base.
Instantaneous velocity: Velocity at a particular instant of
time.
Acceleration: i) Rate of change of velocity. ii) Change of velocity in unit time.
Phase: i) The angle θ = ωt which specifies the displacement as well as the direction of motion of the point executing SHM is known as phase. ii) The state or condition as regards its position and direction of motion with respect to the mean position.
Pendulum: A device consisting of a mass , suspended from a fixed point, that oscillates with a known period.
Simple pendulum: It consists of a small mass oscillating to and fro at the end of a very light string.
Second’s pendulum: A pendulum whose time period is two seconds.
Elastic potential energy: The amount of work done against the elastic force or in compressing an elastic spring.
Free oscillations: Oscillations of a body at its own frequency without the interference of an external force.
Forced oscillations: The oscillations of a body subjected to an external force.
Oscillator: Any system, which is capable of oscillating about a stable equilibrium position.
Harmonic oscillator: i) A physical system under going forced vibrations. ii) A signal oscillator that produces a large number of odd and even harmonics of the fundamental frequency of the input.
Simple Harmonic oscillator(or linear oscillator): It is one in which the restoring force is directly proportional to the displacement with respect to its stable equilibrium position.
Damped harmonic oscillator: An oscillator which moves in a resistive medium.
Magnetron: A type of electron tube used for producing microwaves.
Metal mesh: One of the open spaces between the metal wires of a net.
Elongation: Stretching out to become longer.
Resonance: A specific response of a vibrating system to a periodic force acting with the natural period of the system.
Mechanical resonance: In a mechanical vibrating system, the enhanced response to a driving force as the frequency of this force is increased through a resonant frequency.
Natural frequency: The frequency at which an object or system will vibrate freely.
Natural period: The time period of a body or system for free oscillation.
Electrical resonance: The condition arising when a maximum of current or voltage occurs as the frequency of the electrical source is varied; such as, tuning a radio.
Microwave: An electromagnetic wave with a wavelength in the range 1 mm to 100 mm, i.e. with a frequency in the range 300 to 3GHz.
Oven: A chamber used for baking, heating, or drying.
Microwave oven: An oven in which food is cooked by the heat produced as a result of microwave penetration of the food.
Tacoma Narrow bridge: In November 7, 1940 the first Tacoma Narrows suspension bridge collapsed due to wind-induced vibrations, situated on the Tacoma Narrows in Puget Sound, near the city of Tacoma, Washington, USA. The bridge had only been open for traffic a few months.
Damping: A process whereby energy is dissipated from the oscillatory system.
Damped oscillations: Decreasing in amplitude with time due to the resistance of the medium to the oscillations or vibrations.
Driven Harmonic oscillator: A physical system under going forced vibrations.
Condition for resonance: Resonance occurs when the frequency of the applied force is equal to one of the natural frequencies of vibration of the forced or driven harmonic oscillator.
Dissipation: The removal of energy from a system to overcome some form of resistive force (mechanical or electrical). Without resistance (as in motion in vacuum) there can be no dissipation.
Shock absorber: Any of several devices for absorbing the energy of sudden impulses or shocks in machinery or structure.
Pith ball: A bob or small suspending ball made of some soft , spongy substance.
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