General > General Technical Chat
Physics Question - ma = mg
RJSV:
THANK YOU, DAVID HESS, for mentioning the British units 'SLUG', as mass, (with the corresponding British unit of force I.E. 'POUNDS').
Now my concerns, today, are to merely point out how this thread is bit wild, maybe, for my taste. I mean, you have one person mixing up the two main standard systems, (English and Metric standards).
You've got someone stating that speed is same a mass, I think he got mixed up, thinking inertia increase is same as mass increase, plus some other (yahoo) stating or mis-stating that relativistic effects are major in EVERY situation. So, yeah, mass increases with speed, but...arrghph not practically speaking.
Like I've tried to teach, I think historically, that 'g' came into the picture, in f=mg as 'no suprise' rather than a 'direct' acceleration! The units match, and heck, it's another 'gravity related' deal.
On that subject, probably Newton got to f=ma through some observations / measurements, but also by way of the universal force equation, that is mass x mass divided by separation distance (squared).
So...anyone with a history context would help clarify these questions, as I am merely speculating, on Newton's exploration.
But what I DON'T see is little 'tendrils' of acceleration IE 'g' shooting up past that stationary weight. 'g' is just in the force-related EQUATION, dude.
Word salads. AND then there is the fellow that stated "words don't matter anyway, they are just there to describe stuff."
Uh, ok, so if I owe you money, $100, let's just be loose, and call it '100 cents'.
JohnnyMalaria:
--- Quote from: David Hess on June 23, 2021, 04:40:36 pm ---Go back to the beginning and figure out what is actually being measured. Scales measure *force* and not *mass*. Weight is force.
Units of pounds are force. The Imperial unit for mass is the slug, although in the industry it is more useful to talk about pounds force and pounds mass.
--- End quote ---
This is not true. It depends on which system of measurements you are using. e.g., the British Gravitational system does define pound as a force but the FPS system defines it as a mass. The UK legally defines a pound as 0.454 kilogram and, therefore, is defined as mass.
I was educated in the UK in the 70s and 80s. Pounds were always units of mass and pounds-force (lbf) specifically used to indicate force.
Nominal Animal:
I use either SI units, Planck units, Hartree atomic units, or bananas.
The last one covers all those slugs and pounds and pints and stones and wheelbarrows and such quite nicely, thank you.
I even use decimal degrees instead of arcminutes and arcseconds, to the exasperation of some of my astronomist friends. (I also like to "accidentally" use the word "logy" instead of "nomy", just to see if they're still listening.)
If you use inch ounce-force to measure torque, does the scale depend on whether it is a fluid (fl. oz) or not (notfl. oz)? And what does australia (Oz) have to do with this, anyway?
T3sl4co1l:
What, you don't use bananas for angle too!? 0/10 disappointed.
Tim
TimFox:
To avoid ambiguity, use “oz av” for small forces and “fl oz” (a pronounceable acronym) for volume. 1.5 fl oz is roughly “two fingers”, except here in Chicago where we measure with vertical digits.
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