All Definition Of Physics For Class 9th [A to Z]
![All Definition Of Physics For Class 9th [A to Z]](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjaXX9mzaWoxZaXd1gmrKDRiWtZXuO6BuwoSIg4UYGYOLYA_st9gdGYAWuQENZ_eTp1B5dgJgD3fzHTiR4mwkI4hnIEF0rq-ag5vyeeuSV1tJDqxIoy3cc-q75ciEQFy9It12BQjTLuCvY/s612/istockphoto-939444810-612x612.jpg "All Definition Of Physics For Class 9th [A to Z]")
Acceleration: The rate of change of velocity.
Acceleration due to Gravity: The acceleration produced in a freely falling body due to the gravitational attraction of the earth.
Amplitude: Maximum displacement of particles of the medium from their mean positions during the propagation of a wave.
Angular Velocity: The rate of change of angular displacement of an object in circular motion.
Angular Acceleration: The rate of change of angular velocity.
Archimedes' Principle: When an object is fully or partially immersed in a liquid, it experiences a buoyant force or upthrust which is equal to the weight of liquid displaced by the object.
Audible Range: The range of frequencies of sound which can be heard by the human ears. It is between 20 Hz to 20,000 Hz.
Average Speed: The total distance travelled divided by the total time taken to cover this distance.
Average Velocity: The arithmetic mean of the initial and final velocities over a given period of time.
Balanced Forces: If the resultant of all the forces acting on a object is zero.
Buoyancy: The tendency of a liquid to exert an upward force on an a body placed in it.
Buoyant Force: The upward force acting on an object 'or' a body immersed in a liquid.
Circular Motion: When a body or an object moves in a circular path.
Compression: A part of a longitudinal wave in which the density of the particles of the medium is higher than the normal 'or' general density.
Density: The density of a substance is mass of the substance per unit volume.
Distance: The actual length of the path covered by a moving body, irrespective of the direction in which the body travels.
Displacement: The shortest distance between the initial position and final position of the body along with direction.
Echo: A repetition of sound due to the reflection of original sound by a large and hard obstacle.
Elastic Potential Energy: The energy possessed by a body due to its deformed state 'or' position.
Energy: The ability to do work.
Fluids: The substances which can flow easily.
Force: A push or pull which tends to change the position of rest or of uniform motion, the direction of motion, or the shape and size of a body.
Free Fall: The falling of a body or object from a height towards the earth only under the gravitational force of the earth.
Frequency: Number of complete waves produced per second.
Gravitation: Force with which two objects attract each other due to their masses.
Gravitational Force: The force with which the earth pulls the objects towards its centre is called gravitational force of the earth or gravity.
Gravitational Potential Energy: The work done in raising a body from the ground to a point against gravity.
Inertia: The property of body to oppose any change in its state of rest or of uniform motion in a straight line.
Inertia of Motion: Due to this inertia, a body in uniform motion tends to continue its motion.
Inertia of Rest: It is the inertia due to which a body at rest tends to remain at rest.
Infrasonic Waves: The sound waves of frequency less than 20HZ.
Kepler's First Law of Planetary Motion: The planets move in elliptical orbits around the sun, with the sun at one of the two foci of the elliptical orbit.
Kepler's Second Law of Planetary Motion: Each planet revolves around the sun in such a way that the line joining the planet to the sun sweeps over equal areas in equal intervals of time.
Kepler's Third Law of Planetary Motion: The cube of the mean distance of a planet from the sun is directly proportional to the square of time it takes to move around the sun.
Kinetic Energy: The energy of an object 'or' a body due to its motion.
Law of Conservation of Energy: Energy can neither be created nor destroyed; but it may simply be transformed from one form to another. The total energy before and after the transformation remain constant.
Law of Conservation of Momentum: When two or more bodies act upon one another, their total momentum remains constant 'or' unchanged provided no external forces are acting is called conservation of momentum.
Law of Gravitation: Everybody in this universe attracts every other body by a force which is directly proportional to the product of their masses, and inversely proportional to the square of the distance between them. The force is along the line joining the centers of two bodies.
Longitudinal Wave: A wave in which the particles of the medium vibrate along the direction of propagation of the wave. Sound waves are longitudinal waves.
Loudness: Measures how strong a sound us. Greater the amplitude, greater in the loudness.
Mass: The quantity 'or' amount of matter contained in the body.
Mechanical Energy: The sum of the potential energy and kinetie energy of a body.
Momentum: The product of mass and velocity of an object 'or' a body.
Motion: A body which changes its position with respect to a fixed point.
Negative Work: The force acting on a body displaces it opposite to the direction of work.
Newton's First Law of Motion: A body continues in its state of rest or of uniform motion in a straight line unless an external force acts on it.
Newton's Second Law of Motion: The rate of change of momentum of an object 'or' a body is directly proportional to the applied force, and takes place in the direction in which the force acts.
Newton's Third Law of Motion: Newton's third law of motion state that; for every action, there is an equal and opposite reaction.
Noise: Unpleasant sounds.
Non-uniform Acceleration: If the velocity of an object increases by unequal amounts, in equal intervals of time.
Non-uniform Motion: A body travels unequal distances in equal intervals of time.
Non-uniform Speed: If a moving body covers unequal distances in equal intervals of time.
Non-uniform Velocity: If it covers unequal displacement in equal intervals of time.
Odometer: It is an instrument that indicates distance travelled by a vehicle, such as a bicycle or automobile.
One Joule: The amount of work done when a force of 1 N moves a body through a distance of 1 m in the direction of force.
Pitch: Distinguishes between sounds of some loudness. Greater the frequency greater in the pitch.
Positive Acceleration: When the velocity of an object increases with time.
Positive Work: The force acting on a body displaces it along the direction of force.
Potential Energy: The energy of an object due to its position or change in shape.
Power: The rate at which work is done or energy is consumed.
Pressure: The force acting perpendicularly on a unit area of the object.
Quality: Distinguishes sounds of some pitch and loudness. Depends upon the waveform.
Reference Point: A fixed point with respect of which a body is at rest or in motion.
Relative Density: The ratio of the mass of any volume of the substance to the mass of an equal volume of water.
Rest: An object which does not change its position with respect to a fixed point.
Retardation or Deceleration: If the velocity of the body increases, the acceleration is positive, and if the velocity of a body decreases with time.
Reverberation: The persistence of sound in a hall due to repeated reflection.
Sound: A form of energy which gives sensation of hearing.
Speed of a Wave: Distance travelled by a wave in 1 second.
Speed: Speed of a body is the distance travelled by a body per unit time.
Speedometer: It is an instrument that measures and displays the instantaneous speed of a land vehicle.
Thrust: The force acting on an object perpendicular to its surface.
Time Period: The time taken to complete one complete vibration.
Transformation of Energy: The change of energy one form into another form.
Transverse Wave: A wave in which the particles of the medium vibrate in a direction perpendicular to the direction of propagation of the wave.
Ultrasonic Waves: The sound waves of frequency greater than 20,000Hz.
Unbalanced Forces: If the resultant of all the forces acting on an object is not zero.
Uniform Acceleration: If an object travels in a straight line and its velocity increases by equal amounts in equal intervals of time.
Uniform Motion: If an object travels equal distances in equal intervals of time, no matter how small these time intervals may be.
Uniform Speed: If an object travels equal distances in equal intervals of time, no matter how small these time intervals may be.
Uniform Circular Motion: When a body moves in a circular path with uniform speed or constant speed a body.
Uniform Velocity: If it a body travels in a specified direction in a straight line and moves over equal distances in equal intervals of time, no matter how small these time intervals may be.
Velocity: The distance travelled by an object per unit time, in a given direction.
Wave: A periodic disturbance produced in a material medium due to vibration motion of the particles of the medium.
Wavelength: It is the distance between two consecutive compressions or two consecutive rarefactions.
Weight: It is the force with which a body is attracted towards the centre of the earth.
Work: The product of the magnitude of the force and the distance moved by the body in the direction of force.
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