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Topic Date User

Rope - static v dynamic for top-roping and leading 30-Jan-2012 At 2:34:47 PM Olbert

Message

On 30/01/2012 Dan Theman wrote:
>On 25/01/2012 One Day Hero wrote:
>
>>
>>Oh yeah, I forgot about this one. Mr. engineer seems to think that a
>dynamic
>>rope can 'absorb force'.......like you pull on one end, and the other
>end
>>doesn't feel all the force 'cause its absorbed by the rope somehow!?!?
>>Isaac Newton had a thing or two to say on that topic.
>
>You didn't really think this one through did you? What happens when you
>fall? The rope absorbs the part of the force (like an elastic band), storing
>the energy. The rest goes to the belayers end. The rope then releases the
>energy as you and/or your belayer bounce back up a bit (i.e. the energy
>is used to pull you up). If the belayers end if fixed (as it would be if
>the rope was stuck) then all the energy is transmitted back to you. So
>no, not all the force goes to the stuck end, as it is stored by the rope
>and released as you stop pulling.
>

Ummmm - no. No and no. Isaac Newton had a good deal to say about simple motion, the forces involved in climbing are just an application of his theory.

Dynamic ropes absorb energy.
Dynamic ropes do not absorb force.
The peak level of force is less with a dynamic rope than a static because of the stretch.
The force applied to the anchor point lasts longer with a dynamic rope.
A statically applied force will result in the same resultant force at the other end for a static and dynamic rope.
Tugging on a dynamic will produce a lower peak force at the anchor point than a static, though I agree with ODH that this is probably negligible.