4π2mxT2\frac{4 \pi^{2} m x}{T^{2}}T24π2mx
4π2 m T2 T\frac{4 \pi^{2} \mathrm{~m} \mathrm{~T}^{2}}{\mathrm{~T}} T4π2 m T2
4πmr2 T2\frac{4 \pi \mathrm{mr}^{2}}{\mathrm{~T}^{2}} T24πmr2
πmr2\pi \mathrm{mr}^{2}πmr2