在机场、海港、粮库,常用输送带运送旅客、货物、和粮食等,如图所示,当行李箱随传送

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问题:

在机场、海港、粮库,常用输送带运送旅客、货物、和粮食等,如图所示,当行李箱随传送带一起匀速运动时,下列关于行李箱受力的说法中正确的是(  )

A.行李箱所受的摩擦力方向沿传送带向上

B.行李箱所受的摩擦力方向沿传送带向下

C.此时行李箱受到三个力的作用

D.因为行李箱与传送带之间相对静止,所以行李箱不受摩擦力的作用

考点:滑动摩擦力、动摩擦因数力的合成共点力的平衡
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B The Ancient Olympic Games古代奥林匹克运动会
According to historical records,the first (1) Olympic Games can be traced back to 776 BC.They (2) dedicated to the Olympian gods and were staged on the (3) plains of Olympia.They continued for nearly 12 centuries, (4) Emperor Theodosius decreed in 393 A.D.that aU such"pagan cults" (5) banned.
The oldest myth which concerns the beginning of the (6) Games is that of Idaios Daktylos Herakles.According to other (7) ,Zeus,the father of humanity,fought and defeated Cronus in a (8) for the throne of the gods.Finally,the well-known (9) Herakles is mentioned who staged games in Olympia in honour (10) Zeus,because the latter had helped him conquer Elis when (11) went to war against Augeas.
Through the 12 centuries of (12) Olympic Games,many wonderful athletes competed in the stadium and (13) hippodrome of ancient Olympia’s sacred area,moving the crowds with (14) great achievements.Although mortal,their Olympic victories immortalised them.Of (15) best athletes who left their mark on the sacred vallev (16) Olympia,some surpassed all limits and became legends by winning (17) successive Olympic Games and remaining at the forefront of their (18) for more than a decade.
The ancient Olympic Games were (19) a one.day event until 684 BC.when they were extended (20) three days.In the 5th century B.C.,the Games were extended again to cover five days.


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CW78XX系 * * 端集成稳压器中的调整管必须工作在开关状态下。

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导致西亚地区冲突不断地因素很多,下列哪种因素不是其主要原因是(  )

A.地处“五海三洲之地”,战略地位重要

B.争夺丰富的石油资源和有限的水资源

C.存在明显的宗教信仰差异

D.以畜牧业为主的农业著名

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如图,一长为l的粗细不均匀的水泥电线杆,重心在距A端处,当用竖直向上的力F1将A端抬高h(B端仍在地面上)时, F1做功为W1;当用竖直向上的力F2将B端抬高h(A端仍在地面上)时;F2做功为W2,则F1:F2=________,W1:W2=___________。

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综合运用能力的形成规律,培养和促进学生能力的发展。

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