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roadstead
May 25, 2010, 11:38 PM
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jt512 wrote: roadstead wrote: adatesman wrote: whiskeybullets wrote: Adatesman's link does help to clarify this, if people take the time to read it. Not my link; Roadstead posted it. I posted it for the OP...what you boys did after that is  Threads asking about what a kilonewton is should be exactly this long: 225 lb. Yet every time the question comes up a dozen people have to bring up the distinction between weight (or force) and mass, and that kg is a measure of mass and kN is a measure of force. At that point someone (usually me), feels compelled to explain that there is a simple mathematical equivalence relation between kg and kN, which allows for the sensible and common practice of expressing force (or weight) in kg. On average, only about one or two of the weight–mass pedants understands this, even though it is obvious from their own equations; and thus they argue endlessly about definitions they've memorized but haven't thought very much about. At some point, a parallel discussion about the difference between force and energy (which actually is important in understanding impact forces on gear) emerges, and then all hell breaks loose. Jay
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adatesman
May 25, 2010, 11:39 PM
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jt512
May 25, 2010, 11:52 PM
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adatesman wrote: jt512 wrote: roadstead wrote: adatesman wrote: whiskeybullets wrote: Adatesman's link does help to clarify this, if people take the time to read it. Not my link; Roadstead posted it. I posted it for the OP...what you boys did after that is Threads asking about what a kilonewton is should be exactly this long: 225 lb. Yet every time the question comes up a dozen people have to bring up the distinction between weight (or force) and mass, ... Because they are in fact different, and you are wrong in your assertion that they are the same. Quite simple, really.
Except that I never asserted that they are the same. But congratulations on misrepresenting me without writing "so you're saying."
Jay
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adatesman
May 25, 2010, 11:59 PM
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dugl33
May 26, 2010, 12:04 AM
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kg is to slug as kn is to lbs.
Nice pointless pissy snipefest, though. Give it a rest. No one cares.
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jt512
May 26, 2010, 12:07 AM
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adatesman wrote: jt512 wrote: adatesman wrote: jt512 wrote: roadstead wrote: adatesman wrote: whiskeybullets wrote: Adatesman's link does help to clarify this, if people take the time to read it. Not my link; Roadstead posted it. I posted it for the OP...what you boys did after that is Threads asking about what a kilonewton is should be exactly this long: 225 lb. Yet every time the question comes up a dozen people have to bring up the distinction between weight (or force) and mass, ... Because they are in fact different, and you are wrong in your assertion that they are the same. Quite simple, really. Except that I never asserted that they are the same. But congratulations on misrepresenting me without writing "so you're saying." Jay Perhaps you should start reading your posts, Jay, as this is the second time in this thread where you claim to have not said something when you actually did. No wonder I'm confused about what you're saying... Apparently you don't know either!  jt512 wrote: What a lame article. All you need to know is that the kilonewton is a unit of force equal to 224.8 lb. Jay
No, Aric, rather this is the second time in this thread where you have claimed that I said something that I didn't. The following statement is true and does not imply that weight is the same as mass.
"The kilonewton is a unit of force equal to 224.8 lb."
Jay
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adatesman
May 26, 2010, 12:21 AM
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jt512
May 26, 2010, 12:50 AM
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adatesman wrote: jt512 wrote: No, Aric, rather this is the second time in this thread where you have claimed that I said something that I didn't. The following statement is true and does not imply that weight is the same as mass. "The kilonewton is a unit of force equal to 224.8 lb." Jay Oops, you're right. I misread Kilonewton as Kilogram in that last bit I quoted. So that makes it only one spot in this thread where you said something you later claimed not to have.
No, Aric, that leaves one time in this thread when you claimed I said something that I did not.
In reply to: But when you get right down to it, the OP asked for an explanation of Kilonewtons and the link provided did a really nice job explaining it. What I can't get my head around is why you find it lame.
Because he wasn't asking about the relation between force and mass. If his carabiner was stamped "5400 lb" he would have understood what that meant. Therefore, he almost surely knows that kN must be measuring the same same thing as pounds, with his only interest being how kilonewtons relate to a unit he is more familiar with.
Whenever this question comes up there is a subset of users who insist on extending the answer beyond what is needed to answer the question, by an order of magnitude, which most likely puts understanding the answer beyond the reach of the questioner—and for no good reason.
Jay
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jt512
May 26, 2010, 12:52 AM
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dugl33 wrote: kg is to slug as kn is to lbs. Nice pointless pissy snipefest, though. Give it a rest. No one cares.
Somewhere there's a grumbling old engineer with a slide rule and a pocket protector who disagrees.
Jay
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adatesman
May 26, 2010, 1:04 AM
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jt512
May 26, 2010, 1:11 AM
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adatesman wrote: jt512 wrote: adatesman wrote: So that makes it only one spot in this thread where you said something you later claimed not to have. No, Aric, that leaves one time in this thread when you claimed I said something that I did not. Actually no, it was Gunkie that caught you on it. I merely provided the full quote and link to the post of yours where it occurred.
Gunkiemike didn't "catch me" on anything. He took something I wrote, made a false inference from it, and then attributed his error to me. Then, you quoted him and claimed that I said something that I did not. And then you repeated this claim later in the thread. That makes you at least as guilty as him.
Jay
(This post was edited by jt512 on May 26, 2010, 1:47 AM)
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patto
May 26, 2010, 2:07 AM
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jt512 wrote: Most Americans don't even know what mass is, and, for purposes of understanding the strength of climbing gear, they don't need to. Thanks to gravity being a constant, you don't need to know the mass of a falling object to calculate the impact force on a piece of climbing gear. Jay
Excuse me Jay!? Mass is integral to calculating impact force. You most definately need to know the MASS.
And while I cannot comment from my own knowlege wether a 'pound' is force or mass it seems that according to wiki a 'pound' is MASS. A 'pound-force' is a force and DEFINED in terms of a pound mass.
http://en.wikipedia.org/wiki/Pound
In other words "The kilonewton is a unit of force equal to 224.8 lb." IS NOT CORRECT.
Furthermore furthermore in industry or in home use, when something recommends maximum load of 220lb or 100kgs. They are talking about mass. The manufactures have made assumptions about the safe working loads of the product.
Putting 5000lbs on a carabiner would be highly misleading. People might assume that the carabiner is safe up to 5000lbs in mass. Which is clearly not the case!
It is much more sensible to use newtons because there is little room for misinterpretation.
To top it all off there is little doubt that SI units are far, far easier for calculatations. For example calculating the force required to contstrantly accelerate a car 0-160kph is trivial. Doing the same calculation for 0-100mph is significantly harder.
(This post was edited by patto on May 26, 2010, 5:02 AM)
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patto
May 26, 2010, 2:16 AM
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Being a physics geek I wish to point out that that "There are four fundamentals in the science of mechanics - length, time, mass, and force" is incorrect.
In fact there are only 3, force is trivially defined by the other 3 and so is not independent and not fundamental.
In fact there are only 7 fundamental base units in SI:
http://en.wikipedia.org/wiki/SI_base_unit
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jt512
May 26, 2010, 2:17 AM
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patto wrote: jt512 wrote: Most Americans don't even know what mass is, and, for purposes of understanding the strength of climbing gear, they don't need to. Thanks to gravity being a constant, you don't need to know the mass of a falling object to calculate the impact force on a piece of climbing gear. Jay Excuse me Jay!? Mass is integral to calculating impact force. You most definately need to know the MASS.
The standard equation for the maximum impact force T1 on the climber is
T1 = w + sqrt(w^2 + 2krw) ,
where w is the climber's weight, k represents the elasticity of the rope (not a function of the climber's mass), and r is the fall factor.
You'll have to help me out here: why do I "definately" need to know the climber's "MASS" to calculate the impact force?
The rest of your post is sillier than I have the patience to respond to.
Jay
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dugl33
May 26, 2010, 2:55 AM
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jt512 wrote: patto wrote: jt512 wrote: Most Americans don't even know what mass is, and, for purposes of understanding the strength of climbing gear, they don't need to. Thanks to gravity being a constant, you don't need to know the mass of a falling object to calculate the impact force on a piece of climbing gear. Jay Excuse me Jay!? Mass is integral to calculating impact force. You most definately need to know the MASS. The standard equation for the maximum impact force T1 on the climber is T1 = w + sqrt(w^2 + 2krw) , where w is the climber's weight, k represents the elasticity of the rope (not a function of the climber's mass), and r is the fall factor. You'll have to help me out here: why do I "definately" need to know the climber's "MASS" to calculate the impact force? The rest of your post is sillier than I have the patience to respond to. Jay
Maybe it would be clearer to state one needs to know either the mass and the gravitational constant or the weight?
Assuming calculations here on earth with acceleration being 9.8 m/s^2 or 32 ft/s^2 we're just toggling back and forth between weight and mass, which are used interchangeably in common parlance and practice outside a fairly narrow realm.
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jt512
May 26, 2010, 3:17 AM
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dugl33 wrote: jt512 wrote: patto wrote: jt512 wrote: Most Americans don't even know what mass is, and, for purposes of understanding the strength of climbing gear, they don't need to. Thanks to gravity being a constant, you don't need to know the mass of a falling object to calculate the impact force on a piece of climbing gear. Jay Excuse me Jay!? Mass is integral to calculating impact force. You most definately need to know the MASS. The standard equation for the maximum impact force T1 on the climber is T1 = w + sqrt(w^2 + 2krw) , where w is the climber's weight, k represents the elasticity of the rope (not a function of the climber's mass), and r is the fall factor. You'll have to help me out here: why do I "definately" need to know the climber's "MASS" to calculate the impact force? The rest of your post is sillier than I have the patience to respond to. Jay Maybe it would be clearer to state one needs to know either the mass and the gravitational constant or the weight?
That was clear in the original context: see the comment of adatesman to which I was originally replying. In response to patto et al, who quote my original statement, but ignore the statement to which I was replying, I'm not inclined to voluntarily re-supply the context that they neglected to include.
Jay
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patto
May 26, 2010, 5:35 AM
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jt512 wrote: The standard equation for the maximum impact force T1 on the climber is T1 = w + sqrt(w^2 + 2krw) , where w is the climber's weight, k represents the elasticity of the rope (not a function of the climber's mass), and r is the fall factor.
jt512 wrote: You'll have to help me out here: why do I "definately" need to know the climber's "MASS" to calculate the impact force?
In the unique case where intial velocity is zero then the complete substitution mg=w can be done.
jt512 wrote: The rest of your post is sillier than I have the patience to respond to.
Silly because it indicates that you are wrong? Silly to suggest that the unit of pounds is said to measure MASS acccording to wiki?
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jt512
May 26, 2010, 6:50 AM
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patto wrote: jt512 wrote: The standard equation for the maximum impact force T1 on the climber is T1 = w + sqrt(w^2 + 2krw) , where w is the climber's weight, k represents the elasticity of the rope (not a function of the climber's mass), and r is the fall factor. There is an implicit knowledge of the climbers mass within that equation.
I shouldn't let you get away with this "implicit knowledge" straw man of yours—after all, we either need to know the climber's mass to calculate the impact force or we don't—but I can't resist, because even your claim that the climber's mass is implied by the above equation is wrong.
Let's say r=1, k=10 kN, and w=1 kN. We can calculate T1 in the above model. It's 8.81 kN. You claim that this implies knowledge of the climber's mass. Therefore, do you agree that you should be able to state unequivocally what the climber's mass is? Answer yes or no. If you answer "no," we're done here; we agree that the climber's mass is not implied by the above equation. If you answer "yes," state the mass. The only acceptable answers are "no" or a mass. Any statement of additional assumptions needed to compute the climber's mass implies "no."
Jay
(This post was edited by jt512 on May 26, 2010, 6:51 AM)
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patto
May 26, 2010, 7:20 AM
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jt512 wrote: I shouldn't let you get away with this "implicit knowledge" straw man of yours—after all, we either need to know the climber's mass to calculate the impact force or we don't—but I can't resist, because even your claim that the climber's mass is implied by the above equation is wrong. Let's say r=1, k=10 kN, and w=1 kN. We can calculate T1 in the above model. It's 8.81 kN. You claim that this implies knowledge of the climber's mass. Therefore, do you agree that you should be able to state unequivocally what the climber's mass is? Answer yes or no. If you answer "no," we're done here; we agree that the climber's mass is not implied by the above equation. If you answer "yes," state the mass. The only acceptable answers are "no" or a mass. Any statement of additional assumptions needed to compute the climber's mass implies "no." Jay
http://en.wikipedia.org/wiki/Weight
Lets not play fun and games about variations in the local gravitational acceleration. After all most of us don't 'weigh' ourselves. in the same location as we take lead falls. In fact we aren't 'weighing' ourselves at all on scales, all we are doing is measuring the force our body exerts against the ground.
If you want to play your game then how are you measuring weight? Are you including the 0.1kg you need to add to your body weight to account for your body's buoyancy in air?
But regardless. To quote yourself Jay, this is all 'sillier than I have the patience to respond to.' So I am bowing out.
Suffice to say I have yet been convince that you are right and wikipedia is wrong. Furthermore I think the obvious benefits of SI units over imperial english units should be self evident.
(This post was edited by patto on May 26, 2010, 7:27 AM)
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cantbuymefriends
May 26, 2010, 9:19 AM
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jt512 wrote: patto wrote: jt512 wrote: Most Americans don't even know what mass is, and, for purposes of understanding the strength of climbing gear, they don't need to. Thanks to gravity being a constant, you don't need to know the mass of a falling object to calculate the impact force on a piece of climbing gear. Jay Excuse me Jay!? Mass is integral to calculating impact force. You most definately need to know the MASS. The standard equation for the maximum impact force T1 on the climber is T1 = w + sqrt(w^2 + 2krw) , where w is the climber's weight, k represents the elasticity of the rope (not a function of the climber's mass), and r is the fall factor. You'll have to help me out here: why do I "definately" need to know the climber's "MASS" to calculate the impact force? The rest of your post is sillier than I have the patience to respond to. Jay
I agree to most of what you say here, Jay.
But Mass=Weight, at least for us (mostly) using the SI system (measured in kilogram or lb(m)).
jt512 wrote: Let's say r=1, k=10 kN, and w=1 kN.
I think there's a "g" or two missing in the formula, but I could be wrong.
(This post was edited by cantbuymefriends on May 26, 2010, 9:25 AM)
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chadnsc
May 26, 2010, 12:56 PM
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jt512 wrote: chadnsc wrote: Hmm, I must have hit a wrong number, thanks Jay. Fall Factor: .375 Impact Force Rating: 9.4 Friction Factor: .333 Standard On climber 5.78 On belayer 3.85 On anchor 9.63 Friction-adjusted On climber 6.45 On belayer 4.30 On anchor 10.75 All number in Kn. Edit to add: One question though Jay, what is the difference between 'standard' and 'friction adjusted' and why is the friction adjusted values higher? People here keep saying that the added friction in the system lowers the forces on the climber. I'm not disputing your link; I'd just like to actually know the truth. Read through this thread and/or skim through this paper. If you still have questions, let me know. Jay
Thanks Jay, the links answered all my questions.
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shockabuku
May 26, 2010, 1:07 PM
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cantbuymefriends wrote: jt512 wrote: patto wrote: jt512 wrote: Most Americans don't even know what mass is, and, for purposes of understanding the strength of climbing gear, they don't need to. Thanks to gravity being a constant, you don't need to know the mass of a falling object to calculate the impact force on a piece of climbing gear. Jay Excuse me Jay!? Mass is integral to calculating impact force. You most definately need to know the MASS. The standard equation for the maximum impact force T1 on the climber is T1 = w + sqrt(w^2 + 2krw) , where w is the climber's weight, k represents the elasticity of the rope (not a function of the climber's mass), and r is the fall factor. You'll have to help me out here: why do I "definately" need to know the climber's "MASS" to calculate the impact force? The rest of your post is sillier than I have the patience to respond to. Jay (Bold emphasis above is mine) I agree to most of what you say here, Jay. But Mass=Weight, at least for us (mostly) using the SI system (measured in kilogram or lb(m)). jt512 wrote: Let's say r=1, k=10 kN, and w=1 kN. I think there's a "g" or two missing in the formula, but I could be wrong.
I can't take it anymore. You are exactly wrong.
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chadnsc
May 26, 2010, 1:56 PM
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Jay, Adat,
It's nice that you guys are so helpful with all of this but DAMN!
I mean I get called out for busting Paulbluemounds chops but in this thread you two have far surpassed my tendency for bugging Paul!
Give it a rest guys! I mean those of us intelligent to understand this concept know who's right and who's wrong. Neither of you have nothing to prove to any of us.
Now if the two of you where to team up and use your powers for good . . . or evil, well nothing could stop you! 
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jt512
May 26, 2010, 2:17 PM
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shockabuku wrote: cantbuymefriends wrote: jt512 wrote: patto wrote: jt512 wrote: Most Americans don't even know what mass is, and, for purposes of understanding the strength of climbing gear, they don't need to. Thanks to gravity being a constant, you don't need to know the mass of a falling object to calculate the impact force on a piece of climbing gear. Jay Excuse me Jay!? Mass is integral to calculating impact force. You most definately need to know the MASS. The standard equation for the maximum impact force T1 on the climber is T1 = w + sqrt(w^2 + 2krw) , where w is the climber's weight, k represents the elasticity of the rope (not a function of the climber's mass), and r is the fall factor. You'll have to help me out here: why do I "definately" need to know the climber's "MASS" to calculate the impact force? The rest of your post is sillier than I have the patience to respond to. Jay (Bold emphasis above is mine) I agree to most of what you say here, Jay. But Mass=Weight, at least for us (mostly) using the SI system (measured in kilogram or lb(m)). jt512 wrote: Let's say r=1, k=10 kN, and w=1 kN. I think there's a "g" or two missing in the formula, but I could be wrong. I can't take it anymore. You are exactly wrong.
Whew, I was beginning to think that there was going to be a "what's a kilonewton" thread without someone saying that weight is not a force. I was starting to lose faith in the algorithm. Still waiting for "the rope absorbs the impact force" lead-in for the force vs. energy discussion.
Jay
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beau
May 26, 2010, 2:18 PM
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Thanks everybody for the input, but no one seems to know what kilonewton ratings mean in practical terms for the climber. . .
• the impact force calculator is useless, since I don't know what Fall Factor and Friction Factor are . . .
• and jt512 is right, the article could have stopped at the first line saying 1kn = 225 pounds . . .
The question is, if I weigh 140 pounds, what's my 6kn nut going to do for me if I shock load it, say in a fall of 2 feet, or 10 feet, or 20 feet? The only variables for a computation equation would be 1) weight of the climber, 2) distance of fall, and 3) kn rating of the piece. Am I wrong about this?
Or, to phrase it the other way around, how much would I have to weigh for my 6kn stopper to be useless? Last week my second told me I had placed an incorrect piece because it had only a 6kn rating.
~ beau
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