Surface tension can be described as a force per unit length pulling on the edge of an object.

This gives the average drop in elevation per unit length of river.

The physical model behind this method is the infinite line source with constant power per unit length.

If we write a+bj, this is a quaternion of unit length.

In fact, we want to know the attractive force per unit length of wire 1.

The magnitude of the force per unit length agrees with the expression for shown above.

Lower strings are thicker, thus having a greater mass per unit length.

At greater depths, there are more molecules per unit length to delay the light.

But often, it is easier to deal with vectors of unit length.

Also, one picks a segment in the plane which is declared to be of unit length.