The "critical point test" (aka "scissors test") requires that if any one item fails, nobody should be injured.
A "bend" is a knot that joins two ropes.
A "hitch" is a type of knot that must be tied around another object.
The "whistle test" requires that if all rescuers let go, nobody should be injured.
The discussion about raising explained that "mechanical advantage" is a measurement of how much your rope and pulley system leverages the force than you put into it. This page explains a few terms relating to mechanical advantage. The following pages explain how to calculate mechanical advantage.
A system's mechanical advantage is expressed as a ratio using a colon. For example, a 2:1 or 3:1 system (these are pronounced as a “2 to 1" and “3 to 1"). The first number represents the force on the load and the second number is the force that the rescuers are pulling on the rope. For example, when using a 3:1 system, for every three pounds of load, the rescuers will be holding one pound. This means that the rescuers will only need to pull 100 pounds to raise a 300-pound load.
The following links explain how to rig various mechanical advantage systems:
Mechanical advantage systems can be either simple, compound, or complex.
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