A rock is falling from an embankment of mass $m_a$ at a height of $h$. Below, a fall protection fence catches the rock, dissipating the energy through tension cables to steel posts and then into concrete piles.
How would you calculate the "impact" capacity of the tension cables, steel posts and concrete foundations?
EDIT: At this height, the rock initially has a potential energy of $PE=mgh$. Assuming there are no losses due to friction, bouncing, heat, sound, etc (a very conservative assumption), the potential energy will be mostly converted to kinetic energy, $KE=0.5mv^2$. The fence will absorb this complete energy.
Say the rock hits in the middle of the bay between the two posts. The cables will deflect with the impact of the rock. How do you calculate how much energy the cables absorb and whether the cables have sufficient capacity? How is this different from the applied force?