i believe at short drops the rule of thumb is :
[({Drop in feet}+1) x {weight in pounds} = 'Z' Foot/Pounds of force]. Going beyond 8' or so things getting more complicated, speed becoming more of a component to increase the force more dramatically, and with higher math. So 10', 15' you can know it is gaining quickly towards failure for anything of real mass on a 6k line.
So that at zero drop, 10# has the force of it's own weight [({0' Drop}+1) x {10#}=10'# of force.). Whereby, you could slide it over a 9# sensitivity switch and it would trigger it. And the further you drop it, the more force it will have; but it will always weigh the same, strictly speaking "pounds" only refers to weight, not force; kilonewtons and foot pounds refer to force, taking motion into consideration.
If you drop 10#, 1 foot, it will have ~20foot pounds of force [({1'drop} + 1) x {10#} = 20'# of force]. 4' drop with 10# would be ~50'#s <read : approximately 50 foot pounds (of force)>.
It is similar to: if you drop that force in a 1 square foot area = 50 '#s of force per square foot there. Drop that into 2 square feet landing flatly, then 25'#s of force/square foot etc. In both examples there is a finite calculable amount, accounting for distance and weight, nothing coming about, or disapearing magically. So that a 500# log that drops 5' has ~3000'#s [(5+1) x 500] on a line (probably dropping even further as the line stretches, adding to things!!!!). Now, if that is in a simple pulley redirect, that ~3000'#s of force; powers a 2/1 machine on the redirect/support system (pulley redirects braking force to above load), so the pulley, support/anchor and attatchments take a 6000'#s hit, as the line and friction device take a 3000'# hit! Now that is only realized if you offer that much resistance in opposition (friction) so that running it, would not invoke that much force, only as much as the total 'drag' on the line called out from it.
The Law of Energy Conservation commands that these numbers accumulate like this, for the same reasons as in Mechanical Advantage levers, pulleys, ramps etc. That all that energy x time, distance must be accounted for, arcing a prybar 30"s to move the other end 1" lift gives ~30/1 leverage, a pulley system that you pull 5x as much line (with 5 pulls on load), yields ~5/1 power, a 4'drop increase force adding about 4xload before speed (+ its own force of just being a certain mass sitting still) must be realized strongly. All exactly the same but diffrent, ruled by the same law. That is so pervasive that it demands that all of the archived calories, pressure etc. of fossil fuels, create this dynamic explosive force, for that energy of calories didn't just disapear, energy changes over to diffrent forms, it doesn't appear and disapear. Even 'fertilizer' is an encapsulate of energy, and 'passes it ' to new growth, it all must be accountable, and in balance, for even E=MC squared, for everything is in this balance.
Breakaway lanyard can have 2 systems i think; 1 to deacellerate by having so much give through stretch to buffer the force, also stitches that shear open disapating whatever force that takes. System 2 would be to be a mechanical fuse that would shear/ seperate at so much force; so that you would only incur the weight of a saw drop on your bod, not one caught in a top (then it would shear or 'blow the fuse"). So of the total force of pull, you only oppose 200'#s; so thereby only incur that, and it is trying to deaccelerate it as it goes into that.
