9873210 wrote:
So many bad physics teachers. Next you'll be saying the pound is a unit of force.
We can't really blame the Americans for the nonsense they're taught though.... ??
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9873210 wrote:
So many bad physics teachers. Next you'll be saying the pound is a unit of force.
9873210 wrote:Next you'll be saying the pound is a unit of force.
servodude wrote:9873210 wrote:
So many bad physics teachers. Next you'll be saying the pound is a unit of force.
We can't really blame the Americans for the nonsense they're taught though.... ??
9873210 wrote:So many bad physics teachers. Next you'll be saying the pound is a unit of force.
XFool wrote:9873210 wrote:So many bad physics teachers. Next you'll be saying the pound is a unit of force.
It is! (1 lb force, 2 lbs force, 3 lbs force... usually called 'weight')
Unless joking, I think you mean it is not a Defined (base) Unit of force - unless a standardised value for 'g' is assumed.
odysseus2000 wrote:XFool wrote:It is! (1 lb force, 2 lbs force, 3 lbs force... usually called 'weight')
Unless joking, I think you mean it is not a Defined (base) Unit of force - unless a standardised value for 'g' is assumed.
Pound is mass, not force.
odysseus2000 wrote:When you say lb force you are talking mass x acceleration,
odysseus2000 wrote:or poundals or what ever unit you want to measure force in, but pound, kg, etc are all units of mass, not force.
XFool wrote:odysseus2000 wrote:Pound is mass, not force.
Yes! But a pound of force is still a pound force...odysseus2000 wrote:When you say lb force you are talking mass x acceleration,
Quite so - which I alluded to in my comment about 'g'.odysseus2000 wrote:or poundals or what ever unit you want to measure force in, but pound, kg, etc are all units of mass, not force.
Yes, a "poundal" - force needed to accelerate a mass of one pound at a rate of one foot per second, per second (where a pound mass, a foot and a second are all defined primary units) is the standard definition of the unit of force, in the FPS system of units.
But 32 poundals is still one lb of force (give or take).
https://en.wikipedia.org/wiki/Poundal#Background
odysseus2000 wrote:XFool wrote:Yes! But a pound of force is still a pound force...
Quite so - which I alluded to in my comment about 'g'.
Yes, a "poundal" - force needed to accelerate a mass of one pound at a rate of one foot per second, per second (where a pound mass, a foot and a second are all defined primary units) is the standard definition of the unit of force, in the FPS system of units.
But 32 poundals is still one lb of force (give or take).
https://en.wikipedia.org/wiki/Poundal#Background
We think of mass as weight which is a force, but mass is not a force. For example a mass of 1 lb is considered a weight of 1 lbforce on earth, but 1 lb on the moon would weigh less.
Acceleration due to gravity on earth is 9.81 m per second squared, on the moon it is 1.62 m/s**2. The reason for the square is that the Gravitational acceleration on earth 9.81 m/s per second.
Weights and Measures act wrote: the pound or the kilogram shall be the unit of measurement of mass
...
(b)the pound shall be 0·453 592 37 kilogram exactly.
9873210 wrote:Weights and Measures act wrote: the pound or the kilogram shall be the unit of measurement of mass
...
(b)the pound shall be 0·453 592 37 kilogram exactly.
The pound has been a unit of mass pretty much everywhere (e.g. UK, Canada, US, ...) for as long as there has been a concept of mass. Anybody who says pound is a unit of force is clearly and unequivocally wrong, and a scofflaw.
Pound-force is a different unit, you can tell this because it is spelt differently. You will also occasionally come across the use of kilogram-force, which is spelt differently from kilogram because it is also a different unit.
XFool wrote:
What I said, and I'll say it again because it is true, is that a "pound" can be a defined unit of mass - under the FPS system of measures. But.... it can also be a measure of force - most commonly referred to as 'weight'! This is not a contradiction. You have even said so above in your own comment. It is not "spelt differently" it is still spelled 'pound'.
XFool wrote:I regret now ever starting this...
9873210 wrote:weight means mass
XFool wrote:Wanton silliness abounds...9873210 wrote:weight means mass
Try telling that to a physicist.
We watch with bated breath (well, possibly!) on a daily basis, to see when Wikipedia's egregious 'errors' are corrected.
Finis!
servodude wrote:I'd have quoted "means" myself..but given the prevalence of using "weight" for relative mass expressed in simple mass units, I think they're synonymous enough that one risks problems if you assume how the reader will take it
XFool wrote:Not quite sure what you mean here, servodude. However...
servodude wrote:XFool wrote:Not quite sure what you mean here, servodude. However...
Just that if someone gets a form to fill in with a field for their weight it is not normally entered in Newtons
XFool wrote:
Whereas, "a pound of potatoes" means something else! Although related, obviously. A pound of force? Of course! Torque, in the US, is still measured in pound-force-feet, lbf-inch.
XFool wrote:PS. Anyone mention the spring 'balance' ? I really should shut up now.
XFool wrote:If I need to inflate my car tyres, 40 psi, what's that in pascals/sq cm?
Oh, never mind...
servodude wrote:XFool wrote:If I need to inflate my car tyres, 40 psi, what's that in pascals/sq cm?
Oh, never mind...
you don't need an area when taking about Pascals (they themselves are N/m^2)
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