1.If now I use equation number six, then I find the period, and I find that it takes about 31 hours for this object to go around the Earth.
如果现在用方程，可以算出周期，答案是物体绕地球一圈，要花费31个小时。
2.Only in this context, in order to use equation (13) of the axial force calculations.
只有在这个范围内，才能使用式（13）的轴向力计算式。
3.We can use equation (5) to calculated shear modulus directly.
这样我们就可以直接用公式（5）来计算剪切模量。