A:Touch your eyes.
B:Touch your face.
is my father.
矿井里的升降机,由静止开始匀加速上升,经5s速度达到6m/s后,又以此速度匀速度上升10s,然后匀减速上升,又经10s停在井口.求矿井的深度.
我国的两个内海( )