Block and tackle - efficiency approximation - with friction factor

Description

A block and tackle is a system of two or more pulleys with a rope or cable threaded between them, usually used to lift or pull heavy loads.A more precise estimate of efficiency is possible by use of the sheave friction factor, (which may be obtainable from the manufacturer or published tables. The relevant equation is:

Related formulas

Variables

effmechanical efficiency of the system (equal to one for an ideal frictionless system; a fraction less than one for real-world systems with energy losses due to friction and other causes) (dimensionless)
Ksheave friction factor (which may be obtainable from the manufacturer or published tables) (dimensionless)
Nthe ideal mechanical advantage of the system (which is the same as the number of segments of line extending from the moving block) (dimensionless)
Snumber of sheaves in the purchase (dimensionless)