8. Given that the perimeter of the regular pentagon square $A B C D E$ is $2000 \mathrm{~m}$, two people, A and B, start from points $A$ and $C$ respectively at the same time, walking around the square in the direction of $A \rightarrow B \rightarrow C \rightarrow D \rightarrow E \rightarrow A \rightarrow \cdots$. Person A's speed is $50 \mathrm{~m} / \mathrm{min}$, and person B's speed is $46 \mathrm{~m} / \mathrm{min}$. Then, after $\qquad$ $\min$, A and B will first start walking on the same side.
8. 104 .

Suppose that when person A has walked $x$ edges, A and B start walking on the same edge for the first time. At this point, A has walked $400 x \mathrm{~m}$, and B has walked $46 \times$ $\frac{400 x}{50}=368 x \mathrm{~m}$. Therefore,
$$
368(x-1)+800-400(x-1)>400 \text {, }
$$

and $(368 x+800)-400 x \leqslant 400$.
Thus, $12.5 \leqslant x<13.5$.
Hence, $x=13$. At this point, $t=\frac{400 \times 13}{50}=104$.