Work:
In our day to day life, we use the world ‘work’ very frequently and it means some job. But in science it has a specific meaning.
When force is used on an object and it moves through a distance, we say that work is done.
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For example, when a man lifts a weight to a certain height from the ground, the muscular force which he exerts does work against the force of gravity.
Work is done when a load is lifted, when we lift our body above the ground, when we climb stairs, throw a ball into the air or even when we open a door or crack a nut.
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So in simple words, when force is applied on a body to make it move through a distance, against the force of gravity, work is done. Work always involves overcoming some opposing forces.
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Secondly, when we push some heavy object like a box, we work against the frictional force. So the resistance is either against the force of gravity or the frictional force.
Measuring Work:
It is important to consider how work is measured. When a body is lifted from the ground, work, as we have said above, is done against the force of gravity, and the amount of work done will depend on the height through which the body is raised.
We are therefore concerned with force and the distance through which it acts.
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Thus the measurement of work involves the units of force and distance. In other words, the work done is proportional to both the applied force and the distance through which the force acts. Therefore:
Work = Force x distance
‘Energy’:
Capacity or ability to do work is called energy.
To do any work, energy is used. A body is said to posse’s energy when it is capable of doing work or of overcoming resistance.
Thus work and energy have a strong relationship. Energy is spent, when work is done. Energy is the stored capacity to do work.
Our three main sources of energy are the sun, the atom and the earth’s hot interior.
Power:
In simple term, power is the rate of doing work. The rate at which the work is being done is expressed by the amount of work done.
In other words, it also means the rate at which energy is being consumed. If the rate of energy consumption is fast, so the power will also be higher.
The unit usually employed to measure power is watt. In mechanics power is measured by ‘Horse Power’.
One Horse Power is equivalent to 745.700 watts or 33,000 pounds lifted one foot in one minute. In short. Horse Power is known as h.p.
This unit was devised by the great engineer James Watt and it was his estimate of the rate at which a good horse could work for a few hours, though he deliberately fixed it at a high amount.
It may be added here that the domestic electricity consumption is measured in terms of Kilowatt-hour (Kwh).
Kilo-watt hour is the work performed by one kilowatt of electric power in one hour. Price of electrical energy is based on this unit.