问题 填空题
根据文章内容完成框内短文。
    Our town has a big zoo with a lot of animals in it. There are two old lions. They eat lots of meat every
 day. There are also two big elephants and a little one. They are very kind. They eat much grass every day.
  There are a lot of' monkeys in the zoo, too. Children like them and they like children too. They like
 children because they sometimes give them bread and bananas. They like bananas very much.
     In our zoo there are three black bears and four white ones. They stand on their back legs, hold up their
  arms and play with each other like small children .They love candy very much.
     There are __1__ old lions, __2__ elephants, __3__ bears, and __4__ monkeys in the zoo .The __5__
  like meat. The __6__ eat much grass and the monkeys like __7__ very much. The __8__ like candy, and
  they can hold up their arms and ask for __9__ to eat. The __10__ is a lot of fun.
答案

1. two  2. three   3. seven   4. many    5. lions

6. elephants   7. bananas   8. bears   9. food  10. zoo

单项选择题
探究题

(1)某小组研究“杠杆的使用特点”,器材:有刻度的杠杆、若干个相同的钩码、弹簧测力计等,O为杠杆的支点。实验中,在杠杆P点上挂三个相同的钩码,先后四次用弹簧测力计在Q位置沿不同方向向下拉杠杆,如图1-A、B、C、D 所示,每次都能使杠杆在水平位置平衡。

若以测力计的拉力为动力F1,钩码对杠杆的作用力为阻力F2,“动力的方向”用QR连线与测力计拉力方向所组成的夹角θ表示,且0°<θ≤90°。请仔细观察图1中的操作和测量结果,然后归纳结论。

①实验前,应先调节杠杆在 _________ 位置平衡。这样做,除了可以消除自身的重力影响,还可以方便地测量或读出 _________ 。调节时,如发现杠杆左端偏高,应如何操作: _________ 。

②分析比较图1(A)、(B)与(D)的操作和弹簧测力计指针的位置,可得到的初步结论:阻力、阻力臂一定时,动力随动力臂增大而 _________ (选填:增大或减小)。

③分析比较图1(A)、(B)、(C)和(D)的动力F1的大小与动力方向之间的关系,可得到的初步结论:_________________________。

④某次实验中,用如图2所示的方式悬挂钩码,杠杆也能水平平衡(杠杆上每格等距),但老师却往往提醒大家不要采用这种方式。这主要是以下哪种原因 _________(选填字母)。

A.一个人无法独立操作

B.需要使用太多的钩码

C.力臂与杠杆不重合

D.力和力臂数目过多

(2)如图3所示,长1.6m、粗细均匀的金属杆可以绕O点在竖直平面内自由转动,一个“拉力--位移传感器”竖直作用在杆上,并能使杆始终保持水平平衡。该传感器显示其拉力F与作用点到O点距离x的变化关系如图4所示。图可知金属杆重_________________N。