It is given by the ratio stretching force per unit area to stretch per unit length.
"The New Gresham Encyclopedia" by Various
***
It is easy to check that the right hand side of equation (2.10) is the change in linear momentum density of ﬂuid crossing a unit area of the interface, and the left hand side represents the total force per unit area acting on the ﬂuid.
Effects of permeability and viscosity in linear polymeric gels
The key physical quantity, which is in principle measurable using a surface force apparatus , is the force per unit area acting between two charged planes and their associated electric double-layers.
Effective interactions between electric double-layers
By measuring the gradient of F tot φ (d), it is therefore possible to extract the form of dFφ (d)/dA. dFφ (d)/dA is equal to the force per unit area between two parallel plates with distance of separation d.
Detecting Chameleons through Casimir Force Measurements
Since dF /dd ∝ dF /dA, what is actually measured is equivalent to the force per unit area between two parallel plates.
Detecting Chameleons through Casimir Force Measurements
For Λ ≈ Λ0 , the predicted chameleonic force per unit surface area is very small.
Detecting Chameleons through Casimir Force Measurements
***