1. 過去的事哭也是白費力氣。
   It is no use crying about the past.
2. 他白費力氣想抓住停在花上的蝴蝶。
   He tried in vain to catch the butterfly on the flower.
3. 要我承認錯了，是很費力的。
   It was painful to admit that I was wrong.
4. 雖然這項工作很費力，他仍然很快就做完了。
   Although the work was arduous, he finished it in a short time.
5. 我費力重新安排時間，他卻連想都不想去（喝）另一家。
   I take the trouble to rearrange my schedule, but he do not even want to go another round.

力的英語翻譯：