Momentum is constant
====================

If there is no external force applied to system of objects, the total momentum of this
system remains constant during and after any interactions between objects. The total
momentum of the system is the sum of momenta of every object in this system.

**Conditions:**

#. The system is closed.

**Links:**

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

..
    TODO: rename file
    TODO: vector counterpart of this law

.. py:currentmodule:: symplyphysics.laws.conservation.momentum_is_constant

.. py:data:: time

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

Symbol:
    :code:`t`

Latex:
    :math:`t`

Dimension:
    :code:`time`


.. py:data:: momentum

    :attr:`~symplyphysics.symbols.classical_mechanics.momentum` of the system as a function of :attr:`~time`.

Symbol:
    :code:`p(t)`

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

Dimension:
    :code:`momentum`


.. py:data:: law

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


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