Work as defined in physics is quite
different from the everyday meaning. In physics, we say that work is always the
production of motion against opposition. You cannot do work in the physical
sense unless, by exerting a force, you overcome resistance, when you walk
upstairs you are doing work because you are lifting your weight against the
resistance of gravity.
How much work you do always depends upon the weight you lift
and the distance through which you lift it. If you pull a heavy load along the
ground you are doing work because you are moving a weight against the resistance
due to friction. Here, again, the amount of work you do depends upon the weight
of the load you are pulling and the distance over which you pull it. Work always
the product of force time’s distance.
Work =
force × distance
Since work always involves motion, it follows that if there
is no motion there is no work. Lifting a heavy weight requires work; holding
that weight still does not require work. The unit of work which we shall
consider here is the foot-pound. It is equal to a pound of force moving through a
distance of one foot.
If you weigh 160 pounds and walk up a hill to a height of
100 feet, you have done 160 × 100 or 16000-foot pounds of work
because you have moved your weight against the force of gravity for a distance of
100 feet. If you walk the same distance on level ground, the work the force of
gravity to such an extent, but is overcoming primarily a certain amount of
frictional resistance.
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science