1.0*k*q(t) + m*Derivative(q(t), (t, 2))]])

    We can also solve for the states using the 'rhs' method.

        >>> print(l.rhs())
        Matrix([[Derivative(q(t), t)], [(-b*Derivative(q(t), t) - 1.0*k*q(t))/m]])

    Please refer to the docstrings on each method for more details.
    Nc