⚙️ Work, Energy & Power – Chapter Notes for JEE/NEET 2025 🔋

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 Work :- 

• When a body moves through a certain distance in any direction under the influence of an applied force except the direction perpendicular to the direction of a platform force .

• It is scalar quantity and scalar or dot product .

Work done 

Work done in component form :-

Workdone in component form 

Work done for constant and variable forces :-

Workdone by constant and variable forces

# Work Enegry theorem for constant force :-

Work Enegry theorem

# Work Enegry theorem for variable force :-

Work Enegry theorem 

Power :- 

Time rate at which work is done or rate of doing work is known as power .

Power

Enegry :-

Capacity or ability to do work by a body .

Unit:- Joule

=> Kinetic energy :- 

• It is the enegry which possessed with motion .

• Non - Conservative force

Kinetic Enegry

# Relation between Kinetic energy and Linear momentum :-

Relation b/w Kinetic energy and momentum 

=> Potential Energy :- 

• It is the enegry which is possessed with position .

• Conservative Force 

=> Two important types of potential energy :- 

1. Gravitational Potential Energy :-

It is the energy possessed by the body of its position above the surface of the earth .

Potential Energy 

2. Elastic Potential Energy :- 

Elastic Potential Energy 

Note:- 

• Spring of greater force constant 'k' said to be 'stiffer' .

• spring of smaller force constant 'k' said to be 'soft' .

# Spring potential Energy, Work Enegry theorem :-

Spring potential Energy 

Workdone by spring force

Concept of conservative and non conservative :- 

=> Conservative Force :- 

A force is conservative when workdone bh the net force on a moving particle between the particles initial and final position.

Examples :- • Gravitational force

                      • Spring Force

                      • Potential Energy 

=> Non Conservative :-

 A force is non conservative when the work done by this is dependent on the path being follow the particle are called non conservative force .

Examples :-  • Force of friction

                       • Kinetic energy 

Mechanical energy :-

The mechanical energy of a body is the sum of kinetic energy and potential energy .

Mechanical energy

# Illustration of law of conservation of mechanical energy :- 

Conservation of Mechanical energy 

Collisions :-

1. Elastic collision :-

• A collision in which there is no loss of kinetic energy is called elastic collision .

• kinetic energy is conserved

• Linear momentum

• Total energy is conserved

• The force must be conservative force .

• Practically, there won't be no perfect elastic collision.

2. Inelastic collision :-

•A collision in which there is same loss of kinetic energy is called in elastic collision .

• Linear momentum is conserved .

• Kinetic energy is not conserved .

• Total energy is not conserved .

• Force must not be conservative .

• Practically there won't be no perfect inelastic .

Elastic Collision in 1-D ( dimension)

Elastic Collision in 1D

Inelastic  Collison in 1-D(dimension)

Inelastic Collison in 1D

Kinetic energy is not conserved in inelastic Collison 

Elastic Collision in 2-D(dimension)

Elastic Collision in 2D

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