Introduction

Work Energy and power are fundamental concepts of physics. This topic is firstly introduced in class IX, where we have studied the basics of this chapter. Now, we will briefly examine this concept’s definition, function, and uses. Energy and work are co-related to each other; energy means the ability to do any work, and work means the object’s displacement.

Work, Energy, and Power are important chapters in class 11th Physics. Generally, many questions are asked from this chapter in board exams and other competitive exams. Please go through the notes thoroughly to score good marks in this chapter.

What do you mean by work energy and power?

Definition of work

A work is said to be done when an application of force causes the displacement of an object. The SI unit in which work is determined is called Joules, i.e., 1 J = 1 N ⋅ m = 1 kg ⋅ m²/s². Work is defined as the scalar quality as it only has magnitude and has no directions.

 Mathematical Formula: = (F cos θ )d = F.d 

For example: Suppose you are using thread to pull a curtain over the floor, consider that the curtain is your system, and the force you are applying to pull the curtain is a type of external force. So, let’s say you are pulling on this curtain system by dragging it straight behind you, so the thread is parallel to the earth. If you use the thread to pull the curtain for 1 meter, then it is said that you are doing work on the curtain. 

So, the amount of the work you are doing is equal to the force you are using to pull the box times the distance you moved it. 

According to the work equation, if there is no displacement, then work done is 0 which means no work has been done. It implies that there is no work is done when:-

• Force = zero
• the displacement = 0
• force and displacement make 90-degree angles or mutually perpendicular.

Definition of Energy

Energy is defined as the capacity to do work. In other words, energy is the ability to do work. Energy can neither be created nor be destroyed, it can be converted from one form to another. It is a scalar quantity as it only has magnitude and direction. The SI Unit of energy is Joule. Energy can be found in everything in the universe, whether it is a living thing or a non-living thing. The energy can be divided into types i.e. Kinetic Energy and Potential Energy.

Kinetic energy: It is the form of energy of motion. The kinetic energy of an object is equal to half of its mass, times its velocity squared. 

K.E. = (½) m v²

Where m is mass, v is the velocity of the object 

Potential Energy: The energy due to rest is known as potential energy. It is the form of energy that could be used to do work. One of the most common types of potential energy is gravitational force. 

P.E. = mgh 

where m is mass, g is gravity and h is the height 

Definition of Power

Definition of power in physics defines the rate at which work is done. We calculate it by dividing the work done in joules by the time taken in seconds to complete the work. The SI unit of power is Joule per second. It is also known as watts. It is also a scalar quantity like work and energy as it also has only magnitude and has no direction. The mathematical formula for power is work done divided by the time taken.

P  = w/t

Conclusion

Work energy and power class 11 are some of the important topics for the entrance examination. In primary classes, we have studied only the basis of this chapter but in this class, we will study some advanced level questions from this chapter. Above, we have studied definition, principle, formula, SI units, and examples of the topic work, energy, and power.