Poisson ratio is transverse to axial strain ratio
=================================================

Poisson ratio is a physical quantity equal to the ratio of transverse strain
to axial (or longitudinal) strain in the direction of a deforming force.

**Notes:**

#. The sign convention is as follows: positive strain indicates extension and
   negative strain indicates contraction.
#. The Poisson ratio and the Young modulus are all that is needed to completely
   describe elastic properties of an isotropic material.

**Conditions:**

#. The strains must be small.

**Links:**

#. `Wikipedia <https://en.wikipedia.org/wiki/Poisson%27s_ratio#Origin>`__.

.. py:currentmodule:: symplyphysics.laws.dynamics.deformation.poisson_ratio_is_transverse_to_axial_strain_ratio

.. py:data:: poisson_ratio

    :attr:`~symplyphysics.symbols.classical_mechanics.poisson_ratio` of the material of the deformed body.

Symbol:
    :code:`nu`

Latex:
    :math:`\nu`

Dimension:
    :code:`dimensionless`


.. py:data:: transverse_strain

    :attr:`~symplyphysics.symbols.classical_mechanics.strain` in the transverse (lateral) direction relative to the deforming force.

Symbol:
    :code:`e_transverse`

Latex:
    :math:`e_\text{transverse}`

Dimension:
    :code:`dimensionless`


.. py:data:: axial_strain

    :attr:`~symplyphysics.symbols.classical_mechanics.strain` in the axial direction, i.e. parallel to the deforming force.

Symbol:
    :code:`e_axial`

Latex:
    :math:`e_\text{axial}`

Dimension:
    :code:`dimensionless`


.. py:data:: law

    :code:`nu = -e_transverse / e_axial`


    Latex:
        .. math::
            \nu = - \frac{e_\text{transverse}}{e_\text{axial}}