1 Mechanical engineering Mechanical engineering is the science of natural science and technology as the theoretical basis of technical production prac ...
例1 甲.乙二人各乘一台升降机,甲看见楼房在匀速上升,乙也在匀速上升.乙看见楼房在匀速上升.甲在匀速下降.则他们相对于地面: A .甲上升,乙下降 B .甲下降,乙上升 C .甲.乙都下降,但甲比乙慢 D .甲.乙都下降,且甲比乙快 例2.某日,气象兴趣小组的同学测得风向为东风.风速为3m /s . ...