Block and tackle - efficiency approximation - without friction factor

Description

f is the number of sheaves in the purchase, and there is a roughly % loss of efficiency at each sheave due to friction, then:

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)
Snumber of sheaves in the purchase (dimensionless)
χloss of efficiency at each sheave due to friction (dimensionless)