9 : Shock load
Newton ’ s second law of motion states that :
F = ma
Where :
F is the force applied , m is the mass being accelerated ( or decelerated ), and a is the acceleration ( change in speed over time ).
This simple law affects many elements of work at height and of aerial tree rigging in particular . Consider the simple experiment below :
The orange line on the left is comparatively elastic , and the load is brought to a stop over a long distance . The blue rope is ultra-static , and the load is brought to a stop almost instantly . In both cases the objects have the same mass and were travelling at the same speed , the only difference between the two is how sudden the deceleration has been .
Two similar weights are dropped a similar distance . The image on the right shows the moment when the ropes that are securing the two pieces to the anchors above have just gone taut .
It is quite likely that the sudden stop – the shock load – in the blue system will generate forces significantly greater than in the orange system . This can break ropes , destroy hardware and snap branches out of trees .
© Arboriculture Australia 2022 - 131 -