2.3.1 Evaluating forces in rescue rope systems 1 : Forces in ropes
When a rope is loaded or pulled in one direction with a particular amount of force , it must be loaded in the other direction with the same amount of force or it will move . This is a simple translation of Newton ’ s third law : for every action there must be an equal and opposite reaction .
For this introduction , we can assume that a force applied at one end of the rope is carried through the rope , regardless of whether the rope is straight or passes over a pulley or many pulleys .
2 : Simple mechanical advantage
As shown above , if a load of 1kN ( approx . 100kg ) is applied to the lead side of a rope , a similar load of 1kN must be applied at the fall side or the rope will move .
We must also consider how those loads will affect the anchor point ( s ) for any pulleys or blocks where the loaded rope changes direction .
We have seen that each arm of the rope must be pulled with 1kN . In this simple setup , where both sides of the rope are parallel , it is easy to calculate that the anchor point will experience 2kN of force , in the same direction as both arms of the rope .
This basic principle is the foundation for understanding mechanical advantage , and is crucial for building redirect systems when accessing tree structures .
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