搜题请搜索小程序“爱下问搜题”
问题 填空题

小英同学在超市购物时，用5N的水平力推着一辆小车在水平地面上做匀速直线运动．突然，小英发现前面有一个小孩，她马上用10N的水平力向后拉小车，使小车减速，在减速运动的过程中，小车所受的合力为______N（假设小车所受阻力的大小不变）．

答案

用5N的水平力推着一辆小车在水平地面上做匀速直线运动，小车处于平衡状态，由平衡条件得：f=F1=5N；

当她用F2=10N的力向后拉小车时，小车与地面间的接触面不变、小车对地面的压力不变，因此小车受到的摩擦力f=5N不变，则小车受到向后的拉力和摩擦力作用，故小车受到的合力F=F2+f=10N+5N=15N．

故答案为：15．

判断题

刑事赔偿义务机关包括侦查机关、检察机关、审判机关、监狱管理机关和劳动教养管理部门。
查看答案
单项选择题

Recently, I flew to Las Vegas to attend a meeting. As we were about to arrive, the pilot announced with apology that there would be a slight (16) before setting down. High desert winds had (17) the airport to close all but one runway. He said that we would be (18) the city for a few minutes waiting to (19) . We were also told to remain in our seats meanwhile with our seat belts fastened (20) there might be a few bumps(颠簸). Well, that few minutes turned into about four-five minutes, including a ride that would make a roller coaster(过山车) (21) by comparison. The movement was so fierce that several passengers felt (22) and had to use airsickness bags. As you might guess, that’ s not a good thing to have happen in a(n) (23) space because it only (24) to increase the discomfort of the situation.

About twenty minutes into the adventure, the entire airplane became very (25) There was now a sense of anxiety and fear that could be (26) noticed. Every passenger simply held on for dear life …except one. A (27) was having a good time！ With each bump of the (28) , he would let out a giggle (咯咯地笑)of delight. As I observed this, I (29) that he didn’t know he was supposed to be afraid and worried about his (30) . He neither thought about the past nor about the future. Those are what we gown--ups have learned from (31) . He was (32) the ride because he had not yet been taught to fear it. Having understood this, I took a deep breath and (33) back into my seat, pretending I was (34) on a roller coaster. I smiled for the rest of the flight. I even (35) to giggle once or twice, much to the chagrin(随恼) of the man sitting next to me holding the airsickness bag.

29（）

A.quiet 

B.hot 

C.dirty 

D.crowded
查看答案