Surface force

A surface force is an external mechanical tension that acts on the surface of a body. This distinguishes them from volume force densities that act on the volume of a body.

The distinction between surface forces and volume forces is relevant in fluid mechanics (see also surface tension ) and when differentiating between weightlessness and floating in water .

Examples of surface forces are:

• Wind forces
• Contact forces between two continua
  • Frictional forces
  • contact pressure
• the static buoyancy in liquids or gases (in contrast to the opposing weight force , which is a volume force).

Volume densities, on the other hand, arise from force fields:

• at accelerations , e.g. B. in a vehicle, due to the inertia of the accelerated body parts. In free fall , inertia and gravity balance each other out, which is perceived as weightlessness by humans
• magnetism

The forces perceptible by humans are both surface forces (pressure sensitivity of the skin) and volume forces ( balance organ in the ear). The deformation of the corresponding sensory cells is a prerequisite for perception .