def i_ww(self):
        """
        Second moment of inertia around the width axis.
        :return:
        """
        d_values = []
        for i in range(self.n_pads_l):
            d_values.append(self.pad_position_l(i))
        d_values = np.array(d_values) - self.length / 2
        area_d_sqrd = sum(self.pad_area * d_values ** 2) * self.n_pads_w
        i_second = self.pad_i_ww * self.n_pads
        return area_d_sqrd + i_second