In reply to mike kann:
> (In reply to Robert Durran) No, the opposite way around.
No. I was comparing two factor 2 falls on same rope (therefore same maximum force using the usual analysis) of different lengths (say 2m directly onto the belay and 20m directly onto the belay). In the longer fall more energy is dissipated over a longer distance giving same maximum force. However, the longer fall takes more time, so, apart from being more frightening, more time is spent close to the maximum force (and therefore acceleration) which can theoretically result in more damage. Realistically, however,I suspect the sort of maximum forces experienced in climbing falls with modern ropes and harnesses are unlikely to do any damage however prolonged.
> Think of it in terms of energy. The energy in the fall is constant and energy is a combination of force and time.
Energy dissipated is force x distance (momentum is force x time).
> The longer the time the energy is disappated over, the lower the maximum force.
Yes (if you mean distance, not time) for the same energy, but the two factor 2 falls I was comparing have very different energies to disippate.