Metric system problems

[RallyJeff]

Originally Posted by dellagd

You are correct, lb is a unit commonly used for weight. However, it is actually just another unit for force just like N (Newtons). With the metric system, Newton's second law is commonly written out like this:

F=ma
(Newtons) = (kg) * (m/s^2)

In imperial units:

F=ma
(Pounds) = (slugs) * (ft/s^2)

As you can see, Pounds is analogous to Newtons. Kg is actually analogous to an uncommon unit slugs, which is the actual imperial unit for mass, not pounds.

Its easy to get weight and mass confused

Pounds can be used for force or mass. If you're measuring force in pounds, you use slugs for mass. If you're using pounds for mass, you use poundals for force:

http://en.m.wikipedia.org/wiki/Poundal

This weirdness (plus the fact that a cubic foot of water weighs 62.4 pounds as opposed to some sensible round number) are the two big reasons why I prefer working in metric.