A frog walking in a narrow lane takes 5 leaps forward and 3 leaps backward, then again 5 leaps forward and 3 leaps backward, and so on. Each leap is 1 m long and requires 1 s. Determine how long the frog takes to fall in a pit 13 m away from the starting point.

In each process of going forward and coming backward, it will take 8 s, and he will move 2 m in there 8 s.

Time taken to cover first 8 m: = $\frac{8}{2}\times 8 = 32 \mathrm{s}$

Now after covering 8 m, when he takes five steps, he will fal into the pit. Time taken is 5 s.

Total time = 32 + 5 = 37 s.