3 sentences

1. 他失足前仆，重重地摔在了地上。

   tā shī​zú qián pū, zhòng​zhòng de shuāi zài le dì​shang.

   He tripped and fell forward, hitting the ground hard.

   Source: Dong Chinese Dictionary

2. 他在登山时由于路滑而不慎失足。

   tā zài dēng​shān shí yóu​yú lù huá ér bù​shèn shī​zú.

   He accidentally slipped while climbing the mountain.

   Source: Dong Chinese Dictionary

3. 社会应该给那些失足青年一个改过自新的机会。

   shè​huì yīng​gāi gěi nà​xiē shī​zú qīng​nián yī gè gǎi​guò​zì​xīn de jī​huì.

   Society should give young people who have gone astray a chance to turn over a new leaf.

   Source: Dong Chinese Dictionary