newton (force)

[GasDr]

Could someone explain in simple terms exactly what a Newton (specifically a kilonewton)is, besides kg/m/s?

[Inky]

It's a tasty fig paste wrapped in a pastery shell (sorry, I couldn't resist).

[Strainger]

A kN is the amount of force that a 1000 kg mass exerts due to 1 m/s^2 acceleration, or what a 102.04 kg mass weighs on earth (where acceleration due to earth's gravity = 9.8 m/s^2).

[whc.03grady]

Someone with enough schooling to be an anesthesiologist didn't have to take Physics 101? The mind reels....

[GasDr]

Hey, it's been 20 years since Physics. I don't exactly use kN in my practice everyday. Now if you want to talk about the Boyle's law, Charles' law, gas equations, flow dynamics etc....no problem. I didn't exactly see you give an answer there whc.

[E1skeptic]

Let's go to basics:

Newton's Second Law says that F = m (a), where:
F = force (Newtons, N)
m = mass (Kilograms, Kg)
a = acceleration (meters per square second, m/s2)

1 N (Newton) is the force exerted by a mass of 1 Kg accelerated 1 m/s2 (meter per square second)
1 KN = 1000 N

[dasmoocher]

GasDr--I'll have to second whc's post. An anesthesiologist who's not sure what a Newton is? 20 years or not since physics, isn't that such a simple fact to research for yourself? Wouldn't any physics textbook have this information?

[pluto]

Let's not make this harder than it is. A newton is 4.448 pounds. A kilonewton is 4448 pounds.

Yes, I know the difference between lbs-force and lbs-mass. If something weighs 4.448 pounds it exerts a force of 1 newton.


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"non sunt multiplicanda entia praeter necessitatem"
-- William of Ockham

[Strainger]

And don't forget that 1 kN = 101971.6 grams-force!

[Northern Piper]

like the GasDr, my physics is a bit old, but isn't a Newton a measure of weight, while the gram is a unit of mass? in other words, the mass of an object will be constant, whether on Earth, Mars or on the shuttle, while the weight of that object, measured in Newtons, will be different in each of those situations.

I also seem to recall that in the Imperial system, the pound is the unit of weight, equivalent to the Newton, and the slug is the unit of mass, equivalent to the gram. Have I got that right, or was ol' Doc Bergstrom pulling my leg?

[Mr Thin Skin]

Uh Oh, two different answers.

My little conversion booklet lists a Kilonewton as 224.8 pounds.

A newton is the force required to accelerate a 1 kilogram mass at 1 meter/sec/sec.

Now we all know F=ma, to compute the mass that corresponds to 1000 N in our gravitational field (9.80621 M/s/s, sea level) when simply plug in 1000 for F and 9.80621 for a:

1000=m*9.80621

m=101.976 Kilograms

or,

m=224.858 Pounds (1lb=2.205 Kg, sea level).

Oh, and yes

kilograms are related to newtons as slugs are related to pounds.

And also, I own my life to modern medicine and the work of a good GasDr.

[Strainger]

jti, your last paragraph is correct, but sometimes, for convienience (????), we engineers will sometimes express weight and mass measurements in (unit of mass)force or (unit of force)mass. For example, a gram-force is what an object having a mass of 1 gram weighs on earth. Likewise, a pound-mass (lbm) is the mass of an object that weighs 1 pound on earth.

For a tool that has all these strange units, and then some, download convert.exe from www.joshmadison.com/software. (http://www.joshmadison.com/software.) It's free and very handy for those of you who have to perform frequent unit conversions.

[C K Dexter Haven]

As long as DrGas mentioned gas equations, Boyles' Law, etc...

Did you know that James Watt invented a pote for heating gas (air) that violated Boyle's Law? This lead to the common expression that a Watt's pot never Boyles.

[Mr Thin Skin]

God, CKD

It pains me to read such a bad pun.

Spent too much time watching Rocky and Bullwinkle?

[Strainger]

Dex, :P

The link automatically included the period. I'll try it again - www.joshmadison.com/software (http://www.joshmadison.com/software)

[John W. Kennedy]

(sigh!)

A newton is the force that must be exerted on a mass of 1 kilogram in order for it to accelerate at one meter per second per second. Since one standard gravity is approximately 9.8 meters per second squared, the weight of a one-kilgram mass on Earth is approximately 9.8 newtons.

And for sanity's sake, I'd better add for the sake of all the Yanks here that, no, they're not confused, a US, or short, ton is indeed 2000 pounds, and always has been. A British, or long, ton is 2240 pounds. A megagram, also known as a "tonne" or "metric ton" weighs approximately 2204 pounds.

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John W. Kennedy
"Compact is becoming contract; man only earns and pays."
-- Charles Williams

[GasDr]

Alright, give me a f'n break you two who razzed me. (Once again neither one of you seemed to give me an answer). The reason I ask, is that on a carabiner (an aluminum oval clasp used in rock climbing) is rated at 7kN when stressed along it's short axis and 22kN when stressed along it's long axis. I was simply trying to grasp a concept of how much force this exactly is. I know my scrawny frame won't break it falling 10 feet, but I was curious as to what would. I'm sure I could easily figure it out but after passing gas all day, I'm just too damn tired.

[Strainger]

GasDr, 7 kN = 1574 lb and 22 kN = 4946 lb. If you're exerting that much force on them, you probably have bigger issues going on besides whether the clasp fails or not! :)

Hey, I gotta be nice to him. God forbid that one day I "accidentally" wake up during surgery! :D

[dasmoocher]

GasDr-I wouldn't take any "razzing" by me too seriously. But, come on, why ask what a Newton is (others had given an answer when I posted), when what you really wanted to know what carabiner's (sp?) breaking point is? Why not post that question? I'm sure somebody on the MB has done some climbing and knows what you want to know.

The only thing you know for certain is that whatever you say with certainty--someone will certainly question your certainty. ;-)

[DSYoungEsq]

I am surprised at all of you. Quite obviously, GasDr was trying to find out about that most interesting of concepts introduced with New Math: the NewTon. As many will recall, there was a simplifying movement in math during the middle part of the current century, which led to many bemoaning the difficulty of working with the silly figures of conversion existing at the time. In the case of the ton, the fact that the ton was equivalent to 2200 pounds caused no end of confusion. After all, learning to multiply 22's is not as easy as, say, pretending that a ton is something else.

Given this, it isn't surprising to learn that the NewTon was proposed, equal to 2000 pounds of whatever is being weighed. Multiplying by 2 is substantially easier, thought the proponents, who, apparently, discounted the inability of people to readily add back the three 0's they removed first for the calculation. Satisfied with their new unit of weight, they moved on to Tennessee, where legislators were convinced to equate that most difficult of ratios, pi to 3. Rumor has it they are now working to explain where the extra 10% comes from when athletes give their all.

Sadly, the NewTon has slipped from use. As the New Math foundered over the difficulty of understanding what sets of apples had to do with balancing a checkbook, all the good work of the NewTon was lost. Thus, we lost another wonderful tool for precision in calculation.

Please note that I am assuming GasDr didn't mean to ask about the unit of force, the Newton, defined as the force with which one apple hits one's head when dropped from a tree branch, or the NewtOn, the weight of a certain type of amphibian when carried on one's arm.

[NanoByte]

Well, I'm not a-gassed at GasDr. While many more MDs play golf, sail yachts, fly planes or drink expensive wines, they're all interested more in their sports than in what goes on in the OR. I assume the first thing GasDr did, upon finishing his basic physics course, was sell his textbook for it. I've always been impressed that MDs seldom ever crack a medical book 6 mo after leaving med school. (My physics book agrees, of course, with the corrected answer given in this thread.) Does GasDr also dive off mountains when he gets to the top -- like that Aussie MD?

Ray (a piker hiker)

[elbow]

Well, I don't know physics from jack, but this is the best thread I've read in days!
Of course it's 3:00 a.m. just now, but you guys blow me away sometimes!