Force gauge
Test units of force measurements are most commonly newtons or pounds. The peak force is the most common result in force testing applications. It is used to determine if a part is good or not. Some examples of force measurement: door latch, quality of spring, wire testing, strength ... but more complicated tests can be performed like peeling, friction, texture.
Force density
In fluid mechanics, the force density is the negative gradient of pressure. It has the physical dimensions of force per unit volume. Force density is a vector field representing the flux density of the hydrostatic force within the bulk of a fluid. Force density is represented by the symbol f 
, and given by the following equation, where "P" is the pressure: