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

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

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

See also

• Body force
• Contact force