F=KMA question?

Question

What is the weight in lb.(f) of a 100lb.(m) mass a) when g=32.174 ft/s^2 and b) when g = 31.925ft/s^2

This is how I was told to work it out:

a)
1 lb.(f)= [1lb.(f)s^2/32.174ft.lb.(m)]*[100lb.(m)/1]*[32.174ft/s^2]

=100lb.(f)

I'm confused about the first part of that equation:
(1lb.(f)*s^2)/(32.174ft.lb.(m))
is this just something I should know? How is it derived?

Answer 1

Good job. You are exactly right.

Pound force is definitional. It is not derived. It is defined as 100 lb (mass) subjection to the acceration of 32.174 ft/sec^2.

The whole problem is that we use lb force and lb mass synonomusly when they aren't the same thing. lb force is simply defined as a lb mass subjected to standard gravity.

I know this sounds like Catch-22, but you'll get use to it.