Re: The measure of mass is inertia

In sci.physics, jmorriss@xxxxxxxxxxx
<jmorriss@xxxxxxxxxxx>
wrote
on 8 Dec 2005 08:23:11 -0800
<1134058991.188925.202830@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>:
>
> The Ghost In The Machine wrote:
>>
>> Mass one slug, acceleration 1 ft/sec/sec, force 1 pound-force.
>>
>> Mass one pound, acceleration 1 ft/sec/sec, force 1 poundal.
>>
>> Mass one pound, acceleration 32.1 ft/sec/sec, force 1 pound-force.
>>
>> Mass one kg, acceleration 1 m/s/s, force 1 Newton.
>>
>> Newsgroups reset, followups to sci.physics.
>>
>
>
> Not to quibble (well, yes, I guess) Shouldn't ALL these systems work in
> Newton's First Law equally? Without conversion factors?

A conversion factor is always required here, since one is
talking mass versus force. The conversion factor could
be 1 force unit per mass unit per acceleration unit,
of course -- as is the case with all but the third example
above.

Don Shead, however, gets pounds and pounds-force slightly confused.
(Not to mention mass and inertia.)

>
> If you use the pound force and the pound mass, shouldn't the
> acceleration be in units of such that g =1?
>

One could, but I'm not aware of any such unit offhand. The
length could be approximately 32.1 feet for this new unit,
of course, if one uses pounds and pounds-force. Or one
can use a length unit of 9.805 m if one uses kg and kg-force.

(It turns out the two are equal, as they must be,
by definition.)

Personally, I prefer newtons and kg for scientific work, and
pounds and pounds-force for everyday, although there are
exceptions such as 2-liter soda bottles. :-)

--
#191, ewill3@xxxxxxxxxxxxx
It's still legal to go .sigless.
.

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