Introduction of Work, Energy and Power

The physical quantity said to be done whenever a force acts on a body and the body moves through some distance in the direction of the force, which is the product of magnitude of displacement and the component of force along the displacement, with SI unit joule (J) and dimensional formula [M¹L²T⁻²], is called Work.

The work done when a force acting on a body has a component in the direction of displacement, so that W=Fscos⁡θW=Fscosθ is a positive value, is called Positive Work.

The work done when a force acting on a body has a component in the opposite direction of displacement, so that W = F s cos ⁡θ is a negative value, is called Negative Work.

The work done when either F = 0, or s = 0, or θ = 90°, so that the work done equals zero, is called Zero Work.

The capacity or ability of a body to do work, measured by the amount of work the body can perform, which is a scalar quantity with SI unit joule (J) and dimensional formula [ML²T⁻²], is called Energy.

The energy possessed by a body by virtue of its motion, expressed as K E = \[\frac {1}{2}\]mv², is called Kinetic Energy.

The energy stored in a body or a system by virtue of its position in a field of force or by its configuration is called Potential Energy.

The potential energy associated with an object's height above the ground, expressed as P E_{gravitational} = mgh, is called Gravitational Potential Energy.

The potential energy stored in stretched or compressed materials like springs or rubber bands, expressed as P Eelastic = \[\frac {1}{2}\]kx², is called Elastic Potential Energy.

The rate of doing work, where if an agent does work W in time t its average power is P_av = \[\frac {W}{t}\], which is a scalar quantity with SI unit watt (W) and dimension [ML²T⁻³], is called Power.

The limiting value of the average power as the time interval approaches zero, expressed as P = limΔt→0\[\frac {ΔW}{​Δt}\] = \[\frac {dW}{dt}\]​, is called Instantaneous Power.

The commercial unit of electrical energy, also known as the Board of Trade (B.O.T.) unit, which is the electrical energy consumed by an appliance of 1000 watt in 1 hour, equal to 3.6 ×10⁶ joules, is called Kilowatt Hour.