【简答题】( )决定了轨道的方向,引导列车运动的方向。
【单选题】用甲、乙两个滑轮组分别把质量相等的物体匀速提升到相同高度,甲滑轮组的机械效率比乙高,下列叙述正确的是( )
【简答题】When the lazy days of summer arrive and the schedule is packed with swimming,camp,and family vacations,it can be a challenge to find time for learning. But kids’ reading skills don’t have to grow cold...
【单选题】已知轮系中各齿轮的齿数分别为Z1=20,Z2=35,Z3=10,Z4=30,Z5=60,试求此齿轮的传动比i15=( )。
【单选题】有一对传动齿轮,已知主动轮的转速 n 1 =1000r/min ,齿数 Z 1 =10 ,从动齿轮的齿数 Z 2 =50 ,那么从动轮的转速应当为 n 2 = r/min 。
【单选题】—Where did you pick up the stamp? —It was at the post office ________ we worked in the summer vacation.
【简答题】When the lazy days of summer arrive and the schedule is filled with swimming,camp,and family vacations,it can be a challenge to find time for learning. But kids’ reading skills don’t have to grow cold...
【简答题】小学生英语学习策略包括___,___,___,___,___等。