Work, Energy and Power

Work, Energy, and Power: Introduction

Living beings must perform several life processes to survive. Work, Energy, and Power are the main criteria dependent on each other to carry out these processes. The energy for these processes comes from food. Work can only be done if a force is applied and there is motion or displacement in the force’s direction. The amount of a force applied on an item multiplied by the distance traveled in the direction of the force equals the work done. Work has no direction and merely magnitude. Work is thus a scalar number.

Work: 

Work done (W) on an object is defined as the magnitude of the force (F) multiplied by the distance (s) moved by the object in the direction of the applied force.

Work done = Force × Displacement

W = Fs

• Work has only the value of magnitude and there is no direction.
• TheS.My unit of work is Joule: 

               1 joule = 1 newton × 1 mètre.

• Work can only be done if two requirements are met:

 An item should be subjected to force.

The thing has to be moved.

• A force’s work on an object would be Nil if the object’s displacement was zero.
• A force’s output might be either positive or negative.
• When a force works in the opposite direction of displacement, the work done is negative.
• When the force is in the direction of displacement, the work done is positive.
• To summarize, no work has been completed if:

   There is no displacement.

   There is no force.

   Both the force and the displacement are perpendicular to one another.

Energy:

• An entity with the ability to perform work is said to have energy. 
• A force can be exerted on another object by an object that has energy.
• Energy is transferred from the former to the latter in this process.
• As it gets energy, the second object may move and so perform some work.
• As a result, an object’s energy is assessed in terms of its ability to do labor.
• The joule is the same unit of energy as it is of work (J).

1 J is the amount of energy needed to perform one joule of work.

The kilojoule (kJ) is a greater unit of energy that is sometimes used. 1000 J is equivalent to 1 kJ.

Forms of energy:

• Mechanical energy (potential energy + kinetic energy), heat energy, chemical energy, electrical energy, and light energy are some of the different forms of energy. The various forms of energy have their source and their methods of preservation.

The various forms of energy are as follows-

• Kinetic energy is the energy that is possessed by an object which is in motion.
• It rises in proportion to the object’s speed.
• The kinetic energy of a body moving at a certain speed is equal to the effort done on it to achieve that speed.
• The kinetic energy of an object of mass (m) traveling at a constant velocity (v) is:

Potential energy: It is the energy that it contains as a result of its location or configuration.

• If the energy delivered to an item is not used to induce a change in the object’s velocity or speed, it is retained as potential energy.
• When a thing is lifted via a height, the work done on it against gravity while being raised increases its energy. The gravitational potential energy is the energy present in such an item.
• The gravitational potential energy of a mass (m) elevated to a height (h) above the earth’s surface is calculated as follows:

Ep = mgh

Law of conservation of energy:

Energy can only be converted from one form to another, according to the rule of conservation of energy; it cannot be generated or destroyed.

Before and after the transition, the total energy stays constant.

Potential energy + Kinetic energy = Constant         

 Power:

Power is described as the rate of doing work or it can be the rate of transfer of energy. 

• It measures the speed of work done.
• If an object does a work W in time t, then power is given by: 

Power = Work/time

P = Wt

• The unit of power is Watt, having the symbol W. 

• 1 watt = 1 joule/second or 1 W = 1 J s–1. 
• 1 kilowatt = 1000 watts, 1 kW = 1000 W, 1 kW = 1000 J s–1. 
• The energy consumed in homes, businesses, and industries is commonly measured in kilowatt-hours (kWh).
• 1 kWh is equal to 1000 J s–1 of energy utilized in one hour (or 1 kW).

• 1 kWh = 1 kW × 1h = 1000 W × 3600 s = 3600000 J 1 kWh = 3.6 × 106 J. 

Conclusion

Work, energy and power is the most important chapter asked  as MCQs  in UPSC prelims as well as mains. This is a tricky chapter and a lot of time and devotion is required to prepare for this chapter.So far we have learnt from this chapter is that,  work done (W) on an object is defined as the magnitude of the force (F) multiplied by the distance (s) moved by the object in the direction of the applied force.Energy is an entity with the ability to perform work. And power is described as the rate of doing work or it can be the rate of transfer of energy.