Work, Power and Energy Class 9 Notes Science
Chapter 4th Work, Power and Energy
Work:
When a force acts on an object and the object shows displacement, then it said to be a force has done work on the object.
Work = Force x Displacement
Unit of workdone = Joule
1 joule = Newton x metre
Two conditions need to be satisfied for work to be done:
(i) A force should act on object
(a) The object must be displaced
Define 1 joule work.
1 Joule work is said to be done when 1 Newton force is applied on an object and it shows the displacement by 1 meter.
Energy:-
The capacity of a body to do work is called as energy of the body.
Unit of energy = Joules
1KJ = 1000 J
Forms of Energy:
The various forms of energy are potential energy, kinetic energy, heat energy, chemical energy, electrical energy and light energy.
Kinetic Energy:
The energy possessed by a body due to its motion known as kinetic energy.
Unit of workdone = Joule
1 joule = Newton x metre
Two conditions need to be satisfied for work to be done:
(i) A force should act on object
(a) The object must be displaced
Define 1 joule work.
1 Joule work is said to be done when 1 Newton force is applied on an object and it shows the displacement by 1 meter.
Energy:-
The capacity of a body to do work is called as energy of the body.
Unit of energy = Joules
1KJ = 1000 J
Forms of Energy:
The various forms of energy are potential energy, kinetic energy, heat energy, chemical energy, electrical energy and light energy.
Kinetic Energy:
The energy possessed by a body due to its motion known as kinetic energy.
Energy of an object increases with its speed.
Kinetic energy of body moving with a certain velocity = work done on it to make it acquire that velocity.
Derivation:-
Let an object of mass m, move with uniform velocity u, let us displace it by s, due to constant force F, acting on it
Potential Energy:-
The energy possessed by a body due to its position or shape is called its potential energy.
Kinetic energy of body moving with a certain velocity = work done on it to make it acquire that velocity.
Derivation:-
Let an object of mass m, move with uniform velocity u, let us displace it by s, due to constant force F, acting on it
Potential Energy:-
The energy possessed by a body due to its position or shape is called its potential energy.
Example:-
(i). Spring in stretched conditions or in comparison.
(ii).A body placed at a certain height from the ground.
Gravitational Potential Energy: (GP)
When an object is raised through a height, work is said to be done on it against gravity.
The energy possessed by such an object is called the gravitational potential energy.
Gravitational Potential Energy: (GP)
When an object is raised through a height, work is said to be done on it against gravity.
The energy possessed by such an object is called the gravitational potential energy.
Gravitational PotentialEnergy= work is done in raising a body from the ground to a point against gravity.
Derivation:- Consider a body with mass m, raised through a height h, from the ground, Force required to raise the object = weight of object mg.
The object gains energy to the work done on it.
Work done in both the cases (i) and (ii) is same as a body is raised from position A to B, even if the path taken is different but the height attained is the same.
Mechanical Energy: The sum of kinetic energy and potential energy is called mechanical energy.
Law of Conservation of Energy:
Energy can neither be created nor destroyed, it can only be transformed from one form to another. The total energy before and after transformation remains the same.
Potential energy + Kinetic energy = Constant (Mechanical energy)
A body of mass ‘m’ is raised to height ‘h’ at A its potential energy is maximum and kinetic energy is 0 as it is stationary.
When body falls at B, h is decreasing hence potential energy decreases and V is increasing hence kinetic energy is increasing.
When the body is about to reach the ground level, h = 0, v will be maximum hence kinetic energy > potential energy.
Decrease in potential energy = Increase in kinetic energy
This shows the continual transformation of gravitational potential energy into kinetic energy.
Power:- The rate of doing work by a body is called as power.
Commercial Unit of Energy
Derivation:- Consider a body with mass m, raised through a height h, from the ground, Force required to raise the object = weight of object mg.
The object gains energy to the work done on it.
Work done in both the cases (i) and (ii) is same as a body is raised from position A to B, even if the path taken is different but the height attained is the same.
Mechanical Energy: The sum of kinetic energy and potential energy is called mechanical energy.
Law of Conservation of Energy:
Energy can neither be created nor destroyed, it can only be transformed from one form to another. The total energy before and after transformation remains the same.
Potential energy + Kinetic energy = Constant (Mechanical energy)
A body of mass ‘m’ is raised to height ‘h’ at A its potential energy is maximum and kinetic energy is 0 as it is stationary.
When body falls at B, h is decreasing hence potential energy decreases and V is increasing hence kinetic energy is increasing.
When the body is about to reach the ground level, h = 0, v will be maximum hence kinetic energy > potential energy.
Decrease in potential energy = Increase in kinetic energy
This shows the continual transformation of gravitational potential energy into kinetic energy.
Power:- The rate of doing work by a body is called as power.
Commercial Unit of Energy
Comments
Post a Comment