# Surface force

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Surface force denoted fs 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: normal forces and shear forces. A normal force acts normally over an area and a shear force acts tangentially over an area.

## Equations for surface force

### Surface force due to pressure

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

f = force, p = pressure, A = area on which a uniform pressure acts

## Examples

### Pressure related surface force

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

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

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