Forces in middle/high school texts...

[Externet]

Hi all.

As a kid, learned forces being the unit lbf/Kgf as poundsforce/kilogramsforce. Later at university, the newton showed up.

 

What do current physics teachers/text books teach in USA to youngsters in school ? Newtons or not ? Are lbf/Kgf abolished ? Should they be for a correct start ?

[Janus]

The difference in whether you are using the absolute or gravitational unit systems.

 

In the MKS absolute system, Kg and lbs are mass while newtons and poundals are force. In the gravitational system, Kg-sec^2/m( there is no unique name for mass units.) and slugs are mass while lbs and Kg are force.

 

In the absolute systems Mass is the fundamental unit and force the derived unit, while in the gravitational system, force is the fundamental unit and Mass the derived unit.

[ajb]

I do not know about US school, but the SI unit for force is Newtons.

 

However, there is no 'correct' choice of units, but there are standards. Of course, it may be more convenient to use some other units for specific situations.

[DrP]

I wish you guys would toe the international line and use SI units.. we are bad enough in this country with miles and pints, but at least they don't cause problems internationally. We changed to decimal SI units 35 years ago. You need to also... this is why the first Mars rover was destroyed.

 

Last week we had to send some products to the States... last minute rush changing all the labels and packaging to gallons rather than litres.. If I had it my way we would have just said 'sorry, it comes in Litres'.

 

Get into the 20th century guys!

[studiot]

 

Get into the 20th century guys!

 

 

Why would the americans wish to regress in time?

 

[overtone]

 

 

Get into the 20th century guys!

Why would the americans wish to regress in time?

It wouldn't be a regression, for the US - baby steps, baby steps.

[swansont]

I've always considered lbf and kgf to be an abomination. I never saw them in a physics class I took in college.

[studiot]

Has no one noticed today's date?

[DrP]

Sorry, it 45 years ago for us, not 35. ;-)

 

19/08/2015?? What's special about it? And don't ask me to write it with the month before the day as that would just be dumb. ;-)

[studiot]

So what is the current century?

 

and what was quoted (lightheartedly) from post#4?

 

 

Edit

 

I've always considered lbf and kgf to be an abomination. I never saw them in a physics class I took in college.

 

 

That was probably due to the americans messing up good old imperial engineering units.

 

"A pint of pure water weighs a pound and a quarter."

Goes the old Rhyme.

 

So a gallon of pure water very cleverly weighs ten pounds.

 

How much does a US gallon weigh?

 

Edited August 19, 2015 by studiot

[DrP]

You've still lost me studiot.. sorry.

 

We are in the 21st century. I suggested getting into the 20th century because that is when the rest of the world took on SI units as a world standard.

[studiot]

Or maybe earlier than you think.

 

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

 

The first international agreement listed by 1889.

[DrP]

That was the metre - not the whole system? Whatever, your missing the point, as a Brit, I like America and a lot of Americans but their retarded measurement system is somewhat of an embarrassment. I hate to see a country I feel so related too and LOVE actually, be the butt of international ridicule for their backward measurement system, outdated gun and medical laws and their misguided religious beliefs.

[swansont]

I recently observed some excellent unit-shaming in a laser manual

"The hole spacing also allows direct mounting to imperial tables for non-metric countries (Burma, Liberia and the USA). "

 

The backward countries.

[DrP]

lol - that's funny Swans' - being fair, we still cling to mph and other old weights and measures here too. I was grumpy recently when the brand of tobacco I buy changed from 1/2 ounces to 10g packs. (mainly because 10g is less than half an oz, but more to the convention).

[swansont]

I had a weird experience when I lived in Canada. The produce section sold things in imperial units ($/lb), but the deli was in metric ($/100g).

 

The best part was that ice cream came in 2-liter containers instead of a half-gallon. Buying gas by the liter took a little getting used to, apart from using the Monopoly money. (to be fair, though, US currency looked very bland after I'd gotten used to it)

[studiot]

ISO-Metric is not perfect either.

 

Do you buy one kilogramme of bread or one loaf of bread?

 

And while we are on this why is the kilo (prefix) gramme the base unit?

 

And when we get to volume

 

Is 1 cubic metre or 1 litre better?

Edited August 19, 2015 by studiot

[DrP]

No-one is going to go to the shops to buy 1m^3 of milk. lol.

 

In the end it doesn't matter - as long as we all use the same units... if one or 2 backwater countries do not line up with the rest of the world then who cares... but we need the US to play ball or it just falls apart.

Edited August 19, 2015 by DrP

[Externet]

Do any of you in U.S. have kids on high school in order to find out how they are currently taught about forces/thrust ?

 

Sorry, I have to leave now to the store to get three pounds of sixteen-penny nails.

[Greg H.]

The biggest reason the US hasn't changed is that, frankly, no one wants to pay for it. Just the cost of changing all the highway markers to kilometers, even if only cost say 50 cents a marker, would be in the hundreds of millions. The cost of retooling the factories that produce goods here? Forget it - businesses aren't going to eat that cost.

 

Unless we can get Congress to agree (LOL) and pass a law, it will probably happen sometime between never and the day after that.

 

To be fair though, we do use metric in some areas. You'll see liters on most liquids (Except, oddly, milk and gasoline). In fact, the bottled water I have on my desk is listed as

33.8 FL OZ (1 QT 1.8FL OZ) 1 Liter so you can choose the units of your choice. It's all very diverse.

[overtone]

"The hole spacing also allows direct mounting to imperial tables for non-metric countries (Burma, Liberia and the USA). "

Now that's funny. I don't care who you are, that's funny right there. http://www.google.com/imgres?imgurl=http%3A%2F%2Fi691.photobucket.com%2Falbums%2Fvv273%2FPhiladelphia1776%2FLarry_Cable_Guy_thats_funny_right_t.jpg&imgrefurl=http%3A%2F%2Fwww.sodahead.com%2Funited-states%2Fbreaking-news%2Fquestion-3987483%2F&docid=ACj4auyvtPmhFM&tbnid=80j1EbCb4GBXoM%3A&w=450&h=378&ei=_1XaVdSGGNWmyATWp7vgDQ&ved=0CAIQxiAwAGoVChMIlILh1azAxwIVVROSCh3W0w7c&iact=c&ictx=1

 

 

 

You'll see liters on most liquids (Except, oddly, milk and gasoline).

They aren't retail packaged for export. You'll see pints and the like in the fresh produce section as well. And this:

 

Sorry, I have to leave now to the store to get three pounds of sixteen-penny nails

Nobody builds or repairs houses for export.

 

 

 

Do any of you in U.S. have kids on high school in order to find out how they are currently taught about forces/thrust ?

Mostly, they aren't.

 

Handling the units in physical calculations is a genuine and non-trivial obstacle, in the US system - so it's handled in focused college classes or on the job, pretty much, by the new hire getting familiar with a couple of standard units directly and frequently employed in the particular setting. Very few learn the whole system, or even a large share of it.

Edited August 23, 2015 by overtone

[Mordred]

apart from using the Monopoly money.

TBH I like the majority of Canadian bills. Easy to tell em apart. Most ppl don't know there is also a texture difference between bills for the blind.

 

As a Canuck I find US money bland as well