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问题 填空题

一木块放在水平桌面上，木块对桌面的压力为2N，木块与桌面之间的动摩擦因数为0.4，要将木块水平匀速拉动一小段距离，拉力大小是 N，木块受到的摩擦力是 摩擦力．（填“静”或“滑动”）

答案

滑动摩擦力与正压力成正比，故滑动摩擦力为：Ff=μFN=0.4×2=0.8N；

对物体受力分析，受重力、支持力、拉力和滑动摩擦力，木块做匀速直线运动，

故：F=Ff=0.8N

故答案为：0.8，滑动．

填空题

首字母填空。

     For a long time, Hawii has been a magic name to people who like to t __1__. People on b __2__ sides

  of the Pacific Ocean i __3__ . Their dreams a __4__ include at least one scence of a sunset and it drops

 a glow that lights the skies in quiet o __5__ water.

    The beauty of the islands greeted the first strangers , Polynesian people, who came here in canoes.

    They found the beautiful white sand beaches and the waving palm b __6__ trees, but t __7__ were no

 giant hotel  l __8__ the ones we see nowadays . The first people came to Hawaii n __9__ 200 years

 ago,  but skyscraper (very tall building) hotels have only been built in the l __10__25 years.
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选择题

“十月怀胎，一朝分娩。”母亲孕育胎儿十分辛苦，胎儿在母体内发育的场所是（    ）

A．卵巢

B．输卵管

C．子宫　　　

D．胎盘
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