Page 162 - WCS - Electrical

WORKSHOP CALCULATION & SCIENCE - CITS

EXERCISE 14 : Work, Power and Energy

Heat & Temperature
Introduction
- Work, power, and energy are fundamental concepts in physics that describe the transfer and transformation of
energy in various systems.
Work

- Work is defined as the product of force and displacement in the direction of the force.
Work is said to be done by a force, when its point of application moves in its own direction and is measured by
the product of the force and the displacement of the force in its own direction.

The work is measured by the product of the force applied and the distance though which the body is displaced.
- Mathematically,
Work done =Force applied × Displacement × cos(θ),
where θ is the angle between the force and displacement vectors.

- Work is measured in joules (J) and represents the amount of energy transferred to or from an object.
Units of work are the combined units of force and disaplacement . Force may be expressed in absolute as well
as practical units.
Absolute units of work are erg , joule and foot poundal in C.G.S., M.K.S. and F.P.S. systems respectively. Practical
units of work are gram cm, kg meter and foot pound in C.G.S., M.K.S. and F.P.S. systems respectively.
1 dyne X 1 cm =1 erg
1 newton X 1 meter = 1 joule

1 foot X 1 poundal = 1 foot poundal
1 gram X 1 cm = 1 gram cm
1kg X 1 meter = 1kg meter
1 foot X 1 pound =1 foot pound
1 kg meter = 9.8 joules

1 joule = 107 ¬¬ ergs
The S.I. unit of work is 1 joule which is the work done by a force of moving the body through a distance of 1 meter.
Therefore
1 joule = 1 N x 1 meter = 1 Nm

Also 1 joule = 1 Nm = 105 dynes x 10 2 cm
= 10 7 dynes cm = 10 7 ergs.
1 Newton = 105 dynes
1kg wt = 9.81N

1 pound = 4.448N,
Newton = 0.225 pound.
Absolute units
In C.G.S. system unit of work = 1 erg = 1 dyne x 1 cm
In F.P.S system unit of work = 1 Foot poundal = 1 poundal

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