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hafilax
Jan 16, 2009, 1:57 AM
Post #26 of 27
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Registered: Dec 12, 2007
Posts: 3025
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brenta wrote: hafilax wrote: If I'm bored I might try to incorporate stretch with a Hook's law approximation. I guess I was bored a few months ago, and I wrote a simple model with Hooke's law taken into account, but no friction. Here's a trajectory computed by Octave. I didn't focus on force, because I was interested in the speed at which one would slam into a dihedral if falling during a traverse. I'm a bit too tired tonight to change the model, but the rope modulus is 20 kN, so it's not difficult to estimate it at roughly 2 kN from rope elongation. 
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jt512
Jan 16, 2009, 2:14 AM
Post #27 of 27
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Registered: Apr 12, 2001
Posts: 21904
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cantbuymefriends wrote: tweeek wrote: Now, I am trying to understand dthe forces put onto the rope... If I read correctly, I have been told 2 things... the force is 3x that of gravity, or the force is 3x that of body weight? Sorry, Im not sure if I read that correctly. The reason I ask, is I am wondering if the forces are signifigant enough to warrant me from retiring a rope used in this swing after X amount of uses, as I would with a rope that has been exposed to hard falls while I am climbing. Thanks so much for all your help!!
Neither gravity nor body weight is a force, per se. They just "form" a force when combined. You know, F=m*a (where "a" in this case is gravity) So, "three times bodyweight" means that you take the force that Gravity normally exerts on Your Bodyweight and multiply that by 3. If your weight is 100 kg (220 lbm) the gravitational force on your body is 980 N (almost 1 kN) So 3 times bodyweight means in this case a load or force of about 3 kN. Ok?
I'm calling it a tie for cluelessness. At least the first guy knew he was confused.
Jay
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