Work and Energy

Work energy and power

Work is said to be done when a force applied on the body displaces the body through a certain distance in the direction of force.Mathematically, work is the force-displacement product (for those of you who prefer algebra)

W = F x s cos a

or the force-displacement path integral (for those of you who prefer calculus).

dW =F · ds

Positive work means that force (or its component) is parallel to displacement. Negative work means that force (or its component)is opposite to displacement i.e. In conservative field work done by the force over a closed loop is zero.

Energy is the capacity for doing work. Energy can manifest itself in many forms like mechanical energy, thermal energy, electric energy, chemical energy, light energy, nuclear energy, etc. The energy possessed by a body due to its position or due to its motion is called mechanical energy. The mechanical energy of a body consists of potential energy and kinetic energy.

Potential energy is the energy of a body or a system with respect to the position of the body or the arrangement of the particles of the system.For example, gravitational potential energy is associated with the gravitational force acting on object’s mass; elastic potential energy with the elastic force (ultimately electromagnetic force) acting on the elasticity of a deformed object; electrical potential energy with the coulombic force; strong nuclear force or weak nuclear force acting on the electric charge on the object; chemical potential energy, with the chemical potential of a particular atomic or molecular configuration acting on the atomic/molecular structure of the chemical substance that constitutes the object; thermal potential energy with the electromagnetic force in conjunction with the temperature of the object.

Kinetic energy of an object is the energy that it possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity.

Power is defined as the rate at which work is done. Its unit is watt Power is said to be one watt, when one joule of work is said to be done in one second.

If work is being done by a machine moving at speed v against a constant force, or resistance, F, then since work done is force times distance, work done per second is Fv, which is the same as power. Power = Fv

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