Work
Method of Expressing Degree of Labor
There are two kinds of Raw labor (A,B) shown as follows.
Which work will be hard?
| Raw labor A | Raw labor B |
Work to lift luggage of 10kg by 2m with pulley |
Work to push luggage of 10kg horizontally by 5m by power of 20N |
˜JThe sense of the labor changes depending on the image, skill, the psychological condition, the physical condition.
To evaluate the labor impartially, the physical amount not influenced by man's sense is needed.
A physical amount that is the standard of the labor is "Work. "
Work is expressed by W.
The unit of work is J(joule) in SI.
"Work W" is defined by the product of "Force F" and "Moved distance s".
Actually, let's calculate work.
| Raw labor A | Raw labor B |
Work to lift luggage of 10kg by 2m with pulley |
Work to push luggage of 10kg horizontally by 5m by power of 20N |
| Force:F=98[N] Moved distance:s=2[m] Work:W=196[J] | Force:F=20[N] Moved distance:s=5[m] Work:W=100[J] |
This result is shown below.
Work of A: About 200J
Work of B: 100J
It is understood that A is a serious twice work than B.
Because the labor is physically expressible when "Work" is used, it is possible to judge it objectively.
It is clear that the person who does the work of A is the twice as serious as the person who does the work of B.
Let's confirm the definition of work again.
"Work W" is a product of "Force F" and "Moved distance s".
This definition doesn't depend on the means to move the object.
It is irrelevant to this definition even if the object is moved by the hand or it moves with the machine.
Therefore, work (W=196 J) doesn't change even if the rope of the pulley is pulled with the motor (Or, engine).
"Level of the labor" can be compared by the value of work without any relation to the hand work or the machine.
When working, the motor and the engine consume electricity and the fuel.
Naturally, it is not possible to work if there are neither electricity nor a fuel.
In a word, "Possibility of working" is involved to electricity and the fuel.
We call "Possibility of working" energy.
It depends on the above-mentioned reason though electricity and the fuel are expressed as energy.
The energy of 200J is needed when working about 200J.
On the other hand, it is also possible that electricity and the fuel make the light shine, and make the heater generate heat.
In a word, energy is necessary also for emitting light and generating heat.
To tell the truth, luminescence and generation of heat are work though work was defined by the product of "Power F" and "Moved distance s".
When the human body works, it is necessary to obtain energy from outside of the body.
This is said, "Energy is replenished from meal".
It doesn't come for the heavy load to work if it doesn't move even if it makes efforts.
At this time, energy is chiefly consumed to work (muscular generation of heat etc.) in the inside of the body.
I will bring the point together once here.
"Work" is used as an index of the labor.
"Work" is defined by the product of "Force" and "Moved distance".
In man's work and the work of the machine, work is common standards.
Not only the movement but also luminescence and generation of heat are work.
Work is 0 if there is no energy.
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