Surface force

Surface force denoted f_s is the force that acts across an internal or external surface element in a material body. Surface force can be decomposed in to two perpendicular components: pressure and stress forces. Pressure force acts normally over an area and stress force acts tangentially over an area.

Equations for surface force

Surface force due to pressure

$f_{s}=p\cdot A\$

f = Force p = pressure A = cross sectional area of the moving fluid

Examples

Pressure related surface force

Pressure is in ${\frac {force}{area}}={\frac {N}{m^{2}}}$
Area is a $(length)\cdot (width)=m\cdot m=m^{2}$

Given a pressure of $5{\frac {N}{m^{2}}}=5pascals$ and an area of $20m^{2}$ find the surface force due to pressure.

$5Pa\cdot 20m^{2}=100N$

See also

• Body force