A fall line is also the path that an unobstructed object takes down an inclined plane, or along which an object slides when suspended from a catenary, or the path of a pendulum. Deviation from the fall line consumes energy, usually applied as friction.

For example, skiers who are trying to be badass will take as vertical a fall line as possible down a slope, but when they're going as fast as their nerves can stand they will apply the edges of their skis to push themselves off the fall line and slow down.