πu2g\frac{\pi u^{2}}{g}gπu2
πuπ\frac{\pi u}{\pi}ππu
πu2 g2\frac{\pi u^{2}}{\mathrm{~g}^{2}} g2πu2
πu4g2\frac{\pi u^{4}}{g^{2}}g2πu4