External Force
==============

An external force acts on a single point, with vector components x, y, and z defined in the reference frame.

**Keyword Arguments**

:param str name: Name given to the force.

:param str ref_frame_key: Reference frame in which the vector components of the force are defined.

:param str ref_point_key: Point upon which the force acts.

:param numeric force: Force magnitude.

:param numeric x: X-component of the vector aligned with the force.

:param numeric y: Y-component of the vector aligned with the force.

:param numeric z: Z-component of the vector aligned with the force.