Important physics definitions and principles
(CBSE)
Physics Definition-The branch of science which deals with matter, energy, force,electricity, heat, magnetism and all natural phenomena is known as physics.
Motion- An object which moves from its position as per the time is said to be in motion.As an example moving car, needle of clock etc.
Distance - Total distance covered by an object during its travel is known as distance, distance is a scaler quantity because it is needed only magnitude to represent.Its SI unit is meter.
Displacement -The shortest distance covered by an object during its travel from its initial position to its final position is known as displacement. It is a vector quantity because it is needed magnitude as well as direction to represent itself.
Speed- The distance travelled by an object at per unit time is known as speed . It is a scaler quantity and its SI unit is meter/second.
Velocity - The displacement travelled by an object at per unit time is known as velocity. It is a vector quantity and its SI unit is meter/second.
Acceleration- The rate of change of velocity is known as acceleration. It is a vector quantity and its SI unit is meter/ square second.
Average Speed = total distance covered/ total time taken
Average Velocity = total displacement covered/total time taken
Uniform Motion- When an object moves equal distance in equal intervel of time then it is known as uniform motion.
Non Uniform Motion- When an object moves unequal distance in equal intervel of time then it is known as non uniform motion.
Linear Motion- When an object moves in a straight line then it is known as linear motion, as an ex. moving car.
Centripetal Force - When an object moves in a circular path a kind of force which acts on the object towards the center, it is known as centripetal force.
Cenrifugal Force- When an object moves in a circular path a kind of force which acts on the object from the center and tends to keep it outward to move in a circular path.It is actually friction produced due to centripetal force.Both of these forces are equal but their directions are opposite to each other.
First Law Of Motion- Any object remains in its own position untill an external force is applied on it means if it is at stationery position it will remain on the same position and if it is at moving state it will remain on the same position untill an external force is applied on it.As an ex. a car will remain on the same speed untill an accelerated force is applied on it.
Second Law Of Motion- The acceleration on an object is proportional to the force applied on it and inversely proportional to the mass of the object .It is written as f = ma, where m- mass, a-acceleration and f - force applied on the object.
Third Law Of Motion - Every action has a equal and opposite reaction as an ex.when we push our feet down against the ground, the ground also push back our feet by the same force ,it is that's why we become capable to walk and run.
Inertia- When we apply a force on any object ,it opposes the change in itself as an ex.in a moving bus when a driver suddenly stops the bus, the passenger get structed their head to seat next to them ,it occurs due to inertia the seats attached to bus stops with the bus as well as lower part of the body but upper part of body resist the change of state and remains on the same speed and that's why head structed to the next seat.
Momentum- Momentum is the quantity of motion which is the product of mass and velocity, it is a vector quantity, p = mv where p-momentum, m- mass, v- velocity, its SI unit is kilogram.meter/second square.
Conservation Of Momentum- If two objects collides with each other then the sum of their momentum before the collision is equal to the sum of their momentum after the collision.In other words sum of total momentum in a system always remains constant.
Graviatiational Force- Gravitational force is the force of attraction between two objects in the universe which is proportional to the product of their masses and inversely proportional to the square of the distance between them , F= GMm/d2
Gravity-Gravity is a kind of gravitational force exerted by a celestial body on a particular object, this is the one way phenomena.As an ex. the earth attracts every object by an intesity of 9.8 meter per square second .g= GM/R2
Free Fall- When an object fall towards the earth under the impact of only gravity then it is known as free fall.
Mass- Mass of any object is the amount of matter in it, its SI unit is kilogram.It is a scaler quantity and remains the same in throuhout the universe if object is taken place to anywhere.
Weight -This is the force of attraction by the earth to an object which is equal to the product of mass and earth's gravitational acceleration .w = mg, where w - weight, m- mass and g- gravitational accereration, its SI unit is Newton.
Thrust - Thrust is the force exerted to the object by the surface in which it exist,it acts in a perpendicular direction and depends on the area it acts.
Pressure-The force or thrust per unit area is known as pressure.
P = F/A, where p- pressure, F- force or thrust, A- area on which thrust acts.Its SI unit is pascal(Pa ).
Force Of Buoyancy-The upward force exerted by a fluid to the surface of an immersed object is known as buoyant force or force of buoyancy .It is proportional to the density of fluid.
Archimedes' principle- The bouyant force exerted by a liquid to the surface of a partially or fully immersed object is equal to the weight of the liquid displaced by the object .
Force-The push and pull upon an object by another object is known as force, its S.I unit is newton.F = ma, F- force, m= mass
a = acceleration. Interaction of the force upon the object results it in motion so acceleration produced due to change in position of object.
Work-The product of the force applied on an object and its displacement in the direction of the force is known as work done.The S.I unit of work is joule.W= f d, w- work done,f - force applied, d- displacement in the direction of the force.
Energy- The efficiency of doing work is known as energy, the kinds of energy are mechanical energy, electrical energy, wind energy, nuclear energy, solar energy etc. all the kinds of energy are interconvertible to one another. Its S.I unit is joule.
Mechanical Energy- The kind of energy restored by an object due to the change in its position is known as mechanical energy it is ,it is of two kinds 1) potential energy 2) kinatic energy.
Potential Energy - The efficiency of energy of an stationery object due to its specific postion is known as potential energy, as an ex. a compressed spring, an object displaced up to certain height from the ground. Ep = mgh
Ep- potential energy, m- mass. h-height of the object above the ground.
Kinetic Energy - The efficiency of an object when it is in motion is known as kinatic energy, Ek = 1/2(mv2), where m- mass, v- speed of the object.as an example, a moving car, bullet fired by a gun etc.
Power - The rate of doing work is known as power, P=w/t, where p- power, w- work done, t= time, the S.I unit of power =watt.
Frequency - The number of vibrations or oscillations in one second is known as frequency, its unit is hertz.
Time Period - The time taken by one vibration is known as time period, its S.I unit is second .
Wave Length - The distance between successive rarefaction or compression formed in the medium by a sound wave is known as wavelength of sound wave.
Download class 9 th cbse physics lesson 8 th with complete NCERT solutions of back exercise and questions of inside the chapter published by Future Point Coaching Center, Delhi .Anybody need help please don't hesitate to make a comment.
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Average Speed = total distance covered/ total time taken
Average Velocity = total displacement covered/total time taken
Uniform Motion- When an object moves equal distance in equal intervel of time then it is known as uniform motion.
Non Uniform Motion- When an object moves unequal distance in equal intervel of time then it is known as non uniform motion.
Linear Motion- When an object moves in a straight line then it is known as linear motion, as an ex. moving car.
Centripetal Force - When an object moves in a circular path a kind of force which acts on the object towards the center, it is known as centripetal force.
Cenrifugal Force- When an object moves in a circular path a kind of force which acts on the object from the center and tends to keep it outward to move in a circular path.It is actually friction produced due to centripetal force.Both of these forces are equal but their directions are opposite to each other.
First Law Of Motion- Any object remains in its own position untill an external force is applied on it means if it is at stationery position it will remain on the same position and if it is at moving state it will remain on the same position untill an external force is applied on it.As an ex. a car will remain on the same speed untill an accelerated force is applied on it.
Second Law Of Motion- The acceleration on an object is proportional to the force applied on it and inversely proportional to the mass of the object .It is written as f = ma, where m- mass, a-acceleration and f - force applied on the object.
Third Law Of Motion - Every action has a equal and opposite reaction as an ex.when we push our feet down against the ground, the ground also push back our feet by the same force ,it is that's why we become capable to walk and run.
Inertia- When we apply a force on any object ,it opposes the change in itself as an ex.in a moving bus when a driver suddenly stops the bus, the passenger get structed their head to seat next to them ,it occurs due to inertia the seats attached to bus stops with the bus as well as lower part of the body but upper part of body resist the change of state and remains on the same speed and that's why head structed to the next seat.
Momentum- Momentum is the quantity of motion which is the product of mass and velocity, it is a vector quantity, p = mv where p-momentum, m- mass, v- velocity, its SI unit is kilogram.meter/second square.
Conservation Of Momentum- If two objects collides with each other then the sum of their momentum before the collision is equal to the sum of their momentum after the collision.In other words sum of total momentum in a system always remains constant.
Graviatiational Force- Gravitational force is the force of attraction between two objects in the universe which is proportional to the product of their masses and inversely proportional to the square of the distance between them , F= GMm/d2
Gravity-Gravity is a kind of gravitational force exerted by a celestial body on a particular object, this is the one way phenomena.As an ex. the earth attracts every object by an intesity of 9.8 meter per square second .g= GM/R2
Free Fall- When an object fall towards the earth under the impact of only gravity then it is known as free fall.
Mass- Mass of any object is the amount of matter in it, its SI unit is kilogram.It is a scaler quantity and remains the same in throuhout the universe if object is taken place to anywhere.
Weight -This is the force of attraction by the earth to an object which is equal to the product of mass and earth's gravitational acceleration .w = mg, where w - weight, m- mass and g- gravitational accereration, its SI unit is Newton.
Thrust - Thrust is the force exerted to the object by the surface in which it exist,it acts in a perpendicular direction and depends on the area it acts.
Pressure-The force or thrust per unit area is known as pressure.
P = F/A, where p- pressure, F- force or thrust, A- area on which thrust acts.Its SI unit is pascal(Pa ).
Force Of Buoyancy-The upward force exerted by a fluid to the surface of an immersed object is known as buoyant force or force of buoyancy .It is proportional to the density of fluid.
Archimedes' principle- The bouyant force exerted by a liquid to the surface of a partially or fully immersed object is equal to the weight of the liquid displaced by the object .
Force-The push and pull upon an object by another object is known as force, its S.I unit is newton.F = ma, F- force, m= mass
a = acceleration. Interaction of the force upon the object results it in motion so acceleration produced due to change in position of object.
Work-The product of the force applied on an object and its displacement in the direction of the force is known as work done.The S.I unit of work is joule.W= f d, w- work done,f - force applied, d- displacement in the direction of the force.
Energy- The efficiency of doing work is known as energy, the kinds of energy are mechanical energy, electrical energy, wind energy, nuclear energy, solar energy etc. all the kinds of energy are interconvertible to one another. Its S.I unit is joule.
Mechanical Energy- The kind of energy restored by an object due to the change in its position is known as mechanical energy it is ,it is of two kinds 1) potential energy 2) kinatic energy.
Potential Energy - The efficiency of energy of an stationery object due to its specific postion is known as potential energy, as an ex. a compressed spring, an object displaced up to certain height from the ground. Ep = mgh
Ep- potential energy, m- mass. h-height of the object above the ground.
Kinetic Energy - The efficiency of an object when it is in motion is known as kinatic energy, Ek = 1/2(mv2), where m- mass, v- speed of the object.as an example, a moving car, bullet fired by a gun etc.
Power - The rate of doing work is known as power, P=w/t, where p- power, w- work done, t= time, the S.I unit of power =watt.
Frequency - The number of vibrations or oscillations in one second is known as frequency, its unit is hertz.
Time Period - The time taken by one vibration is known as time period, its S.I unit is second .
Wave Length - The distance between successive rarefaction or compression formed in the medium by a sound wave is known as wavelength of sound wave.
Download class 9 th cbse physics lesson 8 th with complete NCERT solutions of back exercise and questions of inside the chapter published by Future Point Coaching Center, Delhi .Anybody need help please don't hesitate to make a comment.
LINK
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