def specific_speed(Q, H, n=3600.0):
    """Returns the specific speed of a pump operating at a specified Q, H,
    and n.

    .. math::
        n_S = \\frac{n\\sqrt{Q}}{H^{0.75}}

    Parameters
    ----------
    Q : float
        Flow rate, [m^3/s]
    H : float
        Head generated by the pump, [m]
    n : float, optional
        Speed of pump [rpm]

    Returns
    -------
    nS : float
        Specific Speed, [rpm*m^0.75/s^0.5]

    Notes
    -----
    Defined at the BEP, with maximum fitting diameter impeller, at a given
    rotational speed.

    Examples
    --------
    Example from [1]_.

    >>> specific_speed(0.0402, 100, 3550)
    22.50823182748925

    References
    ----------
    .. [1] HI 1.3 Rotodynamic Centrifugal Pumps for Design and Applications
    """
    return n * Q ** 0.5 / H ** 0.75
