1. During autumn, the leaves change color and fall down from the trees.

2. She tripped and went down with a bump.

3. Don't fall down from the stairs.

4. I think a fall will always be penalized.

5. The failure was set down to bad planning.

这些句子展示了"fall down"在不同情境下的应用，包括自然现象、意外事件和计划失败等。希望这些造句对你有所帮助。