# Stress

Written by Jerry Ratzlaff on . Posted in Classical Mechanics

## Stress

Stress ( $$\sigma$$ (Greek symbol sigma) ) or ( $$S$$ ) is the force per unit area of cross-section.  The maximum stress of a material before it breaks is called breaking stress or  ultimate tensial stress.

### Stress formula

$$\large{ \sigma = \frac{F}{A} }$$

Where:

$$\large{ \sigma }$$ (Greek symbol sigma) = stress

$$\large{ F }$$ = force

$$\large{ A }$$ = cross-section area

Solve for:

$$\large{ A = \frac{F}{\sigma} }$$

$$\large{ F = \sigma A }$$

## Longitudinal Stress

The stress imposed on the long axis of any shape. It can be either a compressive or tensile stress.

## Shear Stress

### Shear Stress FORMULA

$$\large{ \tau = \eta \cdot \dot {\gamma} }$$

Where:

$$\large{ \tau }$$ (Greek symbol tau) = shear stress

$$\large{ \eta }$$ (Greek symbol eta) = viscosity

$$\large{ \dot {\gamma} }$$ (Greek symbol gamma) = shear rate

Tags: Equations for Stress