问题
填空题
语音。
1. There are two __________ /'bedrumz/ in the house.
2. They live on the _________ /'twentiiθ/ floor.
3. We must keep __________ /kwai[t/ in the reading room.
4. There are ___________ /fR:ti/ students in our classroom.
5. I have a room with 12 ________ /'FA[z/.
答案
1. bathrooms 2. twentieth 3. quiet 4. forty 5. showers
的铁钉钉入木板中，每打击一次给予的能量为
，已知钉子在木板中遇到的阻力与钉子进入木板的深度成正比，比例系数为k。问此钉子全部进入木板需要打击几次？