In response to Bill Potts comment on my earlier note):
Perhaps I am reading Louis's words literally. (Can it ever be "too"
literally?)
Yes, one certainly MAY say that the downward force of gravity on one
kilogram is about one dekanewton (as Potts stated it). But that is a far cry
from Louis's statement that "a daN is approximately a kg". They cannot BE
("is") the other because they are different kinds of things. The fact that
one quantity of a certain amount may CAUSE another quantity to have a
certain amount (whether or not they have the same number) does not mean that
the two amounts are equal, approximately or not.
If pushing down on your car's acceleraor by 10 mm causes the car to speed up
by 10 km/h, that does not make millimetres (mm) equal to kilometres per hour
(km/h).
Bill states:
> Thus, the numerical values are the same, even though the units are not.
If the units are not units of the same type, the two quantities can never be
equal, regardless of the numbers.
Regards,
Bill Hooper
PS
Potts concluded with this example:
> One could truthfully explain to a layperson that a crane with a capacity of
> 1000 daN is capable of suspending a load of about 1000 kg. Of course, it
> might have problems lifting it at more than a snail's pace without something
> failing.
Quite true, except it is not the speed (snail's pace or other) that affects
this situation. It is the rate at which that speed changes (the
acceleration) that is critical. If the operator could get it started, the
crane could lift the 1000 kg at any speed whatsoever.
Bill
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Keep It Simple!
Make It Metric!
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