The general effort force equation for block and tackle to raise or pull a load can be expressed as
S=F/μn
where
S
is the effort force,
F
is the load force (often the weight of the object to be moved),
μ
is the mechanical efficiency of the system (1 in an ideal, massless, frictionless system of pulleys), and
n
is the number of ropes between the sets of pulleys.
