Work, Energy and Power

Work, Energy and Power: What The Chapter is All About

Work Energy and Power are the most important terms used in Physics that the students learn in school early on. Work and energy are the two sides of a coin as both are interconnected to each other. Work is referred to as the displacement of an object when a force (push or pull) is applied to it while energy is referred to as the capacity to do the work. It exists in various forms like potential, kinetic, chemical, thermal, nuclear, electrical energy and so on. Power is the work done per unit of time. Studying work energy power is important in terms of both acquiring knowledge and getting higher marks in the exam.

Physics Work and Energy

When an object moves towards the direction of the force applied, then work is said to be done. But for work to be done energy is the most important thing as it is the ability to work. When work is done by animals or humans, they get the energy from food and when work is done by machines, they get energy from electricity or fuel. 


Work is done when a force produces some kind of motion. For example, when a man climbs a mountain, work is done because while climbing a mountain he is moving against the force of gravity. Hence, work depends upon two factors. They are: 

  • Magnitude of force

  • The direction in which the body moves due to the force applied.

Hence, work is measured by the product of displacement and force of a body along with its direction of the force. It is referred to as scalar quantity and the SI unit of work is Joule. The equation thus stands as:

[Image will be uploaded soon]

Work = F * S

If a body is displaced by S while a Force F acts on it, in such a case

Work W = FS Cos (angle between the displacement and force)

One thing to note here is that force is said to work when it produces a motion in an object. For example, a man tries to move a wall but the wall does not move, hence the work done by the man is zero as there is no displacement produced. But he does lose energy because in his attempt to push the wall he stretches his muscles and thus feels tired. 

Thus, this shows that work doesn't need to be done whenever a force is applied to an object. Work is only done when the force applied can change the direction of the object or move it. 


The capacity of a man that allows him to do work is called energy. In simple words, energy is the ability to work. It is in scalar quantity and has only magnitude and no direction. energy can neither be created nor destroyed, it can only change in its form. Energy can be found in many things, and so there are many forms of energy. The most important types of energy are kinetic energy and potential energy

Kinetic energy refers to the energy of a body due to its movement or motion. It is referred to the work that is required to accelerate a body of the given mass differentiating it from its velocity. While acceleration after the body gains energy, it maintains kinetic energy until its speed changes. The formula of kinetic energy is – 1/2mv2 

Hence from the formula given above, we can state:

1. The kinetic energy of a body gets doubled whenever its mass gets doubled.

2. If the mass of a body is halved, then the kinetic energy is also halved.

3. The kinetic energy of a mass increases by four times when the velocity doubles. 

Power Definition Physics 

Work power or simply power is referred to as a physical concept that includes several meanings, depending on the context and the details available. Power can be defined as the rate of doing work. Power is the energy that is consumed per unit of time. It is present in scalar quantity as it does not have any direction. The SI unit of power is Joules/second and is termed as Watt. Watt refers to the power needed to do one Joule of work in a second. 

Difference Between Work and Power 

The differences between work and power are mentioned in the following table:



Work is referred to as the process of energy that is transferred to an object’s motion by applying force. It is generally represented as the product of displacement and force.

Power is the amount of energy that is transferred in a unit of time. 

The SI unit of work is Joule (J)

The SI unit of power is Watt (W)

The formula for calculating the force is Work = Force * Displacement.

The formula of calculating power is Power = Work/Time

Work can be done in various other measures like kWh, MWh, GWh and volt (eV)

Energy can be measured in units like GW, MW and kW.

Work does not depend on time.

Power depends on time. 

FAQs (Frequently Asked Questions)

1. Define Power in Physics.

Ans: Power can be defined as the rate at which work is done per unit of time. The SI unit of power is Watt (W) (which is calculated as joules per seconds). Earlier, power also referred to activity. It is a scalar quantity. The equation to measure power is P = W/t. The output power of any motor is referred to the product of a torque that a motor generates. The power that is involved in moving the motor is known as the product of traction force on its wheel and its velocity. 

2. What is the Difference Between Work and Energy?




A parallel relationship exists between displacement and the force components.

Energy is the result of the task performed.

Work = force * distance

There are different equations of energy depending on its kind.

Work is positive when the force is applied in the same direction of displacement.

There is no direction component present in energy.

Work was conceptualized in 1826

The term ‘energy’ was coined before 4BC

Employment appears to be negative when the force applied is in the other way of displacement.

There is no direction component present in energy. 

Students Also Read