Work-Energy and Power: What is Work, Law of Conservation of Energy (For CBSE, ICSE, IAS, NET, NRA 2022)

Get unlimited access to the best preparation resource for UGC : Get detailed illustrated notes covering entire syllabus: point-by-point for high retention.

  • Work, power, and energy are among the most important concepts of mechanics.
  • Work, energy, and power are the most used terms in Physics. They are probably the first thing you learn in your Physics class.
  • A moving car, walking upstairs, lifting heavy objects, an aeroplane flying, etc. are among the most common examples that give us insight into the concept of work, power, and energy.
  • Work and energy can be considered as two sides of the same coin. In this article, we will learn all about the concept of work, power, and energy.
  • There are few common notions of work, power, and energy that can be precisely defined in physics.
  • Notions and measurements can be utilized to define and predict the motion and behavior of bodies.
The Work Energy and Power
What is Work, Energy and Power?
DefinitionWork is said to be done when a force applied to an object moves that object.
FormulaWe can calculate work by multiplying the force by the movement of the object.

W = F × d

UnitThe SI unit of work is the joule (J)
DefinitionIn physics, we can define energy as the capacity to do work.
FormulaFor the potential energy the formula is

P. E. = mgh

UnitThe SI unit of energy is joules (J) , which is named in honour of James Prescott Joule.
DefinitionPower can be defined as the rate at which work is done i.e.. energy converted.
FormulaThe formula for power is

P = W/t

UnitThe unit of power is watt (W) .

What is Work?

Work is the measurement of energy transfer that takes place when an object is displaced by an external force applied in the direction of the displacement.

What is Power?

The rate of doing work is called power.

What is Energy?

  • The capacity for doing work is called Energy.
  • All forms of energy are either kinetic or potential.
  • The energy in motion is known as Kinetic Energy whereas Potential Energy is the energy stored in an object and is measured by the amount of work done.
  • It may exist in kinetic, potential, thermal, chemical, electrical, nuclear, or various other forms. The SI unit of energy is the same as that of work.

Types of Energy

  • Mechanical energy
  • Mechanical wave energy
  • Chemical energy
  • Electric energy
  • Magnetic energy
  • Radiant energy
  • Nuclear energy
  • Ionization energy
  • Elastic energy
  • Gravitational energy
  • Thermal energy
  • Heat Energy

What is the Principle of Conservation of Energy?

Principle related to the conservation of mechanical energy states that the total mechanical energy of a substance remains in equilibrium if the only forces acting upon the body are conservative in nature.

Law of Conservation of Energy

  • Energy can neither be created nor be destroyed So, it can be changed from one to another form.
  • Total energy in an isolated system remains the same or energy is conserved over time.
  • Mass remains the same in any closed system within boundaries except for the heat form which can cross boundaries.
  • Energy cannot be created and neither can be destructed but conveniently can be changed to different forms.
  • Chemical energy can be converted into heat energy which could further be used to generate potential energy in a different body.
  • As energy is changed from one to another form, net gain/loss remains the same.
  • So, energy is said to be conserved wherein the total amount remains the same.