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# Surface forces

Article Id: WHEBN0015657789
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 Title: Surface forces Author: World Heritage Encyclopedia Language: English Subject: Continuum mechanics Collection: Publisher: World Heritage Encyclopedia Publication Date:

### Surface forces

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

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

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