【单选题】如图甲所示,放在水平地面上的物体,受到方向不变的水平推力F的作用,F的大小与时间t的关系和物体运动速度v与时间t的关系如图乙所示。下列判断正确的是( )
【简答题】A.They are paying for his education. B.They invited him to their party. C.They took him on a vacation with them. D.They let him live with them for free.
【简答题】She took the boy _____ thehand and led him _____ the zero. A.in…by B. on…at C. at…in D. by…round
【多选题】设计行车速度目标值为250km/h时,双线隧道不应小于 [填空(1)] ㎡,单线隧道不应小于 [填空(2)] ㎡
【单选题】如图甲所示,放在水平地面上的物体,受到方向不变的水平拉力 F 的作用,其 F-t 和 v-t 图象分别如图乙、丙所示,下列说法正确的是 ( )
A.
当 t=2s 时,物体处于静止状态,摩擦力是 0
【单选题】城市道路环形交叉口的环道设计车速为路段设计行车速度的( )。
【多选题】设计行车速度目标值为300km/h、350km/h时,双线隧道不应小于 [填空(1)] ㎡,单线隧道不应小于 [填空(2)] ㎡。
【判断题】TB10621-2009规定旅客列车设计行车速度为250~350km/h。()
【判断题】设计行车速度目标值大于300km/h时,双线隧道横截面积不应小于100m2
【单选题】It took him ten years to complete it. That's how long _____to do it.