Pound a unit of force

[MuddyBoots]

While all for accuracy myself, I should be fully aware of the degree of absolute and literalistic thinking exhibited by some on TLF (and other BBs). After all, by now, I have surely had enough experience!

My fault for originally being a bit flippant?

So, I didn't get the memo that posting on TLF was actually the same thing as taking a Viva for an Oxford Natural Sciences Tripos! Or is that Cambridge? I'm sure I wouldn't know....


PS. Anyone mention the spring 'balance' ? I really should shut up now.

Ha ha, it took me ages to get over the shock of my Physics teacher telling us that the centrifugal force doesn't really exist, we should talk about centripetal force instead. And when he insisted that we shouldn't talk about letting the cold in on a winter's night, it's the heat which goes out of the house! It all seems so topsy-turvey as William Gilbert used to say.

[XFool]

Ha ha, it took me ages to get over the shock of my Physics teacher telling us that the centrifugal force doesn't really exist, we should talk about centripetal force instead. And when he insisted that we shouldn't talk about letting the cold in on a winter's night, it's the heat which goes out of the house! It all seems so topsy-turvey as William Gilbert used to say.

It's a bit like experiencing the "force of gravity". In most normal circumstances you never actually experience gravity. What you feel (weight) is actually the effect of the electromagnetic force opposing gravity by stopping you falling through the ground!

[Spet0789]

This is a really silly debate!

Tell Pratt and Whitney that the pound cannot be a unit of force. Or better still, try and stand behind one of their engines at full chat!

Of course pound is technically a unit of mass, but given 99.999999% of us will spend our entire lives in an environment where any mass is acted on by a damn-near constant gravity, it’s a perfectly reasonable shorthand.

[servodude]

This is a really silly debate!

Tell Pratt and Whitney that the pound cannot be a unit of force. Or better still, try and stand behind one of their engines at full chat!

Of course pound is technically a unit of mass, but given 99.999999% of us will spend our entire lives in an environment where any mass is acted on by a damn-near constant gravity, it’s a perfectly reasonable shorthand.

...until it gets used to specify a torque

The number of times I've seen something "just a bit out" is probably the same as the number I've seen "out by nearly a factor of 10"

[XFool]

This is a really silly debate!

I agree!

Tell Pratt and Whitney that the pound cannot be a unit of force. Or better still, try and stand behind one of their engines at full chat!

Of course pound is technically a unit of mass, but given 99.999999% of us will spend our entire lives in an environment where any mass is acted on by a damn-near constant gravity, it’s a perfectly reasonable shorthand.

[Arborbridge]

What fun this thread is. Maybe one for pedant's corner. I don't really know what to say, except that a lb measures mass. That's it, really.

As for what you would feel behind Pratt and Whitney's engines, I guess it would be "deafened" or maybe "hot".


Arb.

[XFool]

What fun this thread is. Maybe one for pedant's corner. I don't really know what to say, except that a lb measures mass. That's it, really.

So I just need to ensure my car tyres are inflated to the correct mass per unit area of pressure?

This reminds me of a similarly silly debate a few years ago now - was it on here or was it on TMF? - about whether 12 midnight was the end of the day or the start of a new day. There were those who held it was the end of the day, so it couldn't possibly be the start of a new day; and those who held it was the start of the day so it couldn't possibly be the end of the previous day.

For myself I had no difficulty feeling it was both; the end of one day and the start of a new one at the same time.

Despite whatever ISO may have had to say about the matter.

As for what you would feel behind Pratt and Whitney's engines, I guess it would be "deafened" or maybe "hot".

But seemingly you feel you would remain unmoved...

[servodude]

What fun this thread is. Maybe one for pedant's corner. I don't really know what to say, except that a lb measures mass. That's it, really.

So I just need to ensure my car tyres are inflated to the correct mass per unit area of pressure?

This reminds me of a similarly silly debate a few years ago now - was it on here or was it on TMF? - about whether 12 midnight was the end of the day or the start of a new day. There were those who held it was the end of the day, so it couldn't possibly be the start of a new day; and those who held it was the start of the day so it couldn't possibly be the end of the previous day.

For myself I had no difficulty feeling it was both; the end of one day and the start of a new one at the same time.

Despite whatever ISO may have had to say about the matter.

As for what you would feel behind Pratt and Whitney's engines, I guess it would be "deafened" or maybe "hot".

But seemingly you feel you would remain unmoved...

surely the traditional question is whether midnight is 12 am or pm?
In which case it is both (ante and post meridiem) and noon is neither - despite what badly structured forms might attest

[XFool]

So I just need to ensure my car tyres are inflated to the correct mass per unit area of pressure?

That reminds me: You can measure "pressure" in millimetres, inches (or feet)!

A whole new Silly Debate looms.

[Mike4]

So in imperial, what IS the unit of force?

Skimmed the whole thread hoping to find out but no dice. Then mebbe that's the wine...

[servodude]

So in imperial, what IS the unit of force?

Skimmed the whole thread hoping to find out but no dice. Then mebbe that's the wine...

asleep at the back again?

for those what have to deal with older British technical manuals (and sods) it's the "pound force" or pound to its friends - lbf for short

If you are in a US high school (...isn't this where we came in?) they might tell you the pound is simply and categorically only a unit of force (and that God says it can never refer to mass )
- they're wrong but it's not nice to keep reminding them

i think the whole debacle stems from the ambiguity in what "weight" means - i.e. force or mass depending on context
..but I'm not really sure and it's nearly time for the pub

[XFool]

So in imperial, what IS the unit of force?

The 'poundal'. Force needed to cause one pound of mass to accelerate at one ft per sec per sec.

https://en.wikipedia.org/wiki/Poundal

"...and that is the poundal, which is approximately 1⁄32 pound force."

So, one lbf (pound force) is approx. 32 poundals.

I am sure this was mentioned up thread.

[kempiejon]

https://lemonfool.co.uk/viewtopic.php?p=646171#p646171

[XFool]

https://lemonfool.co.uk/viewtopic.php?p=646431#p646431

[9873210]

This is a really silly debate!

Tell Pratt and Whitney that the pound cannot be a unit of force. Or better still, try and stand behind one of their engines at full chat!

Of course pound is technically a unit of mass, but given 99.999999% of us will spend our entire lives in an environment where any mass is acted on by a damn-near constant gravity, it’s a perfectly reasonable shorthand.

Well done on the order of magnitude, about 700 out of about 100 billion people have been in space.

However in my experience the people most insistent that pounds is a unit of force are American astronautical engineers, who are precisely the people for which a constant gravitational field is not true. Isp should be measured in meters/seconds not seconds.

[Arborbridge]

So in imperial, what IS the unit of force?

Skimmed the whole thread hoping to find out but no dice. Then mebbe that's the wine...

asleep at the back again?

for those what have to deal with older British technical manuals (and sods) it's the "pound force" or pound to its friends - lbf for short

If you are in a US high school (...isn't this where we came in?) they might tell you the pound is simply and categorically only a unit of force (and that God says it can never refer to mass )
- they're wrong but it's not nice to keep reminding them

i think the whole debacle stems from the ambiguity in what "weight" means - i.e. force or mass depending on context
..but I'm not really sure and it's nearly time for the pub

At 11.58pm it would have been a good time for the other debate on 12am/pm

[Spet0789]

This is a really silly debate!

Tell Pratt and Whitney that the pound cannot be a unit of force. Or better still, try and stand behind one of their engines at full chat!

Of course pound is technically a unit of mass, but given 99.999999% of us will spend our entire lives in an environment where any mass is acted on by a damn-near constant gravity, it’s a perfectly reasonable shorthand.

Well done on the order of magnitude, about 700 out of about 100 billion people have been in space.

However in my experience the people most insistent that pounds is a unit of force are American astronautical engineers, who are precisely the people for which a constant gravitational field is not true. Isp should be measured in meters/seconds not seconds.

Even in low Earth orbit, gravity still acts at 80% of the force on the surface! So the number of people who have experienced a far weaker gravity field is even fewer - 25ish I would think.

Despite any issues with units, American astronautical engineers seem to manage quite well! Further underlining the pedantry on display from some here…

[servodude]

Well done on the order of magnitude, about 700 out of about 100 billion people have been in space.

However in my experience the people most insistent that pounds is a unit of force are American astronautical engineers, who are precisely the people for which a constant gravitational field is not true. Isp should be measured in meters/seconds not seconds.

Even in low Earth orbit, gravity still acts at 80% of the force on the surface! So the number of people who have experienced a far weaker gravity field is even fewer - 25ish I would think.

Despite any issues with units, American astronautical engineers seem to manage quite well! Further underlining the pedantry on display from some here…

If you stay in one set of units you'll be fine; if you don't you get the Mars Climate Orbiter situation.

As I've mentioned before it's really only torque where I've had difficulties because it matters converting to g-cm if it's lb-ft or lbf-ft

[GoSeigen]

Even in low Earth orbit, gravity still acts at 80% of the force on the surface! So the number of people who have experienced a far weaker gravity field is even fewer - 25ish I would think.

Despite any issues with units, American astronautical engineers seem to manage quite well! Further underlining the pedantry on display from some here…

Hmm, in low earth orbit I'm not sure they "experience" any gravity as such! I should think their experience is far closer to 0% gravity than 100% gravity.

GS

[MuddyBoots]

Despite any issues with units, American astronautical engineers seem to manage quite well! Further underlining the pedantry on display from some here…

And IT uses both units, my laptop and mobile phone screens are measured in inches and weight in lbs.