Mass is constant
================

The mass is constant in a system that is closed, and mass is not transformed to energy.

**Conditions:**

#. System in a closed impenetrable volume, that is, molecules/atoms cannot leave it and
   they are always inside.
#. Mass is not transformed to energy, for example due to annihilation.

**Note:**

#. SymPy does not have a proper way to represent constant mass. We use it's derivative
   over time instead. Derivative of the constant value is zero.

**Links:**

#. `Wikipedia <https://en.wikipedia.org/wiki/Conservation_of_mass>`__.

.. py:currentmodule:: symplyphysics.laws.conservation.mass_is_constant

.. py:data:: time

    :attr:`~symplyphysics.symbols.basic.time`.

Symbol:
    :code:`t`

Latex:
    :math:`t`

Dimension:
    :code:`time`


.. py:data:: mass

    :attr:`~symplyphysics.symbols.basic.mass` as a function of :attr:`~time`.

Symbol:
    :code:`m(t)`

Latex:
    :math:`m{\left(t \right)}`

Dimension:
    :code:`mass`


.. py:data:: law

    :code:`Derivative(m(t), t) = 0`


    Latex:
        .. math::
            \frac{d}{d t} m{\left(t \right)} = 0