Ahhh, takes me back. (Imperial units in primary school, CGS introduced in secondary and MKS in the latter half of university degree course.)
Talking about the miniscule size of many CGS units, one of our physics lecturers quipped that an erg (cm-dyne) was the average energy expended by a fly doing a push-up.
As we (Australia) metricated long ago - and unlike USA we actually DID do it - I am largely metric in weights and measures but generally move fairly well between both systems. The exceptions where I remain unapologetically imperial are peoples' heights (ft,ins) and tyre pressures (psi).
When it comes to atmospheric pressure (context: weather) I still call them millibars rather than the hectopascals which the met guys have switched to. What's with this non-10^3-based trend?
currently re-reading "The First World War: A Complete History" by Martin Gilbert. Good book, terrible war.
**********************************
John Larkin, President Highland Technology, Inc
jlarkin at highlandtechnology dot com
formatting link
Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom laser controllers Photonics and fiberoptic TTL data links VME thermocouple, LVDT, synchro acquisition and simulation
Yup. My mum's dad, Murdo Nicolson, joined up on the first day of the war and spent over 3 years on the Western Front with the Royal Winnipeg Rifles. He was in almost all of the major Canadian battles--St. Julien, the Somme, Passchendaele, Vimy Ridge, and so on, and by the end was one of only about 50 left from the original complement of 1000 or so men in his battalion. Here's a story about him that I ran across in a book:
formatting link
. I know it was he, because it's the right battalion, and the author uses his first name elsewhere. (He calls him "Murdoch Nicholson", which is close but not quite right.)
He lived to be 87, so I knew him pretty well. He almost never talked about the war.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics
160 North State Road #203
Briarcliff Manor NY 10510
845-480-2058
hobbs at electrooptical dot net
http://electrooptical.net
Quoted: __ In this very different usage the meter term represents the distance traveled or displacement in the direction of the force, and not the perpendicular distance from a fulcrum as it does when used to express torque.
-- end quote
Instead of perpendicular pressure against a fulcrum, it is linear displacement distance in the direction of the force.
Calling it a "unit of torque" is a misnomer.
It is a "moment of torque", which relies on a unit of force and a unit of measure to derive and define the moment of torque applied to a fulcrum. Is that "rotational force" Yes, but the term allows it to be defined by using a fixed arm length.
It is linear too. 12 inch pounds (pounds inch) is one foot pound (pounds feet). It also works on the force measure. 16 ounce inches is the same as one pound inch, with the difference being that it simply sounds odd to declare "one pound inch" when "16 ounce inches" sounds a lot more precise.
We could use it as other measures too, but we don't.
Heck, add a 'per second' and it becomes velocity, and add a 'per second per second' and it becomes acceleration, though the linear measure is all one needs for that.
--
John Larkin, President Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com
Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators
Use some common sense. If you are at sea level when you start, the air already in the tube is at that pressure. Since ANY bicycle pump gauge is going to state ZERO pounds at that point, I'd say that such a device NEVER uses "absolute" pressure. Everything will always be relative to the standard pressure at the location the pump (and gauge) device is in.
You are correct. It does not have to move and will not if the point to which the force is applied is fixed. Many times they are not, but there are times when motion is a factor for the distance of a small measure. A force transducer moves a certain amount, then stops, based on the force placed against its "platen". That movement could be in the form of mere microns in distance, but there was movement, and a greater force imposes a larger movement over the operating range of the transducer. It defines it, in fact, which is why one acquires the "size" one needs for the task being performed.
Force transducers oriented to be used as weight scales are ratioed (is that a term?) by way of an arm, a fixed fulcrum, and a pressure point along the length of the arm. The location of the pressure point determines the ratio of the pressure applied to the force transducer. Yep. At the "moment" of measurement nothing is moving.
Even on a rotating shaft, the "measure" is an instantaneous value as if the shaft (or fulcrum) was/were fixed. This is why it is called a "moment of torque". It is like having the meter attached to it while it spins. Of course the shaft diameter can be the entire torque arm, or there can be a physical arm, or tooth, or other protrusion. The calibrated devices and agreed upon science and industry terminology gives us references we can become "familiar with" firsthand and have "a feel for".
Folks who have actually sheared the thread off various threaded holes or nuts base materials have a more intimate knowledge of where "torque" plays into fastener topics.
Things move as torque interplays with what it is applied against usually.
The other use of the term seems archaic (likely) (do we not use joules?) and seems to point at acceleration rate or force of acceleration or such.
Nothing wrong with mm.Hg. (AKA Torr). I think the high vacuum guys still use those. I remember 10^-7 torr being a good CRT vacuum. Ol' Torricelli has been largely forgotten.
--
"For a successful technology, reality must take precedence
over public relations, for nature cannot be fooled."
(Richard Feynman)
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.