I noticed that the impact force going from...
I noticed that the impact force going from pounds force to kilonewtons does not add up in the item description. 4800 lbf should be about 21.4 kN, not 7.2 kN. So what is the correct breaking strength for this cord, 21.4 kN or 7.2 kN?
That is a good question. Usually the tensile (static) strength is in lbf. and the breaking (dynamic) strength is in kN. Since this is a static cord the breaking strength is weaker because this should be used only for static conditions (anchors, etc). I think i am right, hope this helps!
lbf and kN are both units of force. I would guess it is a typo. From Sterling Ropes website, the mean breaking strength is 4271 lbf/19.0kN
The impact force of a rope refers to what the force of impact would be on a climber if he/she took a fall of factor 1.77. Therefore the figure would mean the impact force would only be 7.4kN. Whether this number is actually correct or not, I have no idea...
Backcountry wrote the specs correctly.
The breaking weight for static loads is 4800 lbs. Meaning you can hang anything less than that weight from this rope.
The 7.4kN rating refers to impact. Not meaning that this will cushion a fall to only be 7.4kN (it has no stretch and will not cushion a fall at all) but rather that 7.4kN of force will break the cord. That can be generated very easily by a body in motion. A fall factor 1 will generate over this much force. So make sure there is not slack is the system.
Lots of great info here: http://dmmclimbing.com/knowledge/how-to-break-nylon-dyneema-slings/
Worth a read .... http://wallrat.com/PDF_Files/forcesinleadfalls.pdf