题干

一端装有定滑轮的粗糙斜面体放在地面上,AB两物体通过细绳连接,并处于静止状态(不计绳的质量和绳与滑轮间的摩擦),如图7所示.现用水平力F作用于物体B上,缓慢拉开一小角度此过程中斜面体与物体A仍然静止.则下列说法正确的是  (  )

A:水平力F不变

B:物体A所受斜面体的摩擦力一定变大

C:物体A所受斜面体的作用力不变

D:斜面体所受地面的支持力一定不变

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D

同类题1

今年两会上,“海绵城市”被写入政府工作报告,成为社会热点。请阅读以下材料,完成下列小题。

       材料一:目前我们城市的排水管理要求的是“随降随排”,雨水落到硬化地面只能从管道里集中排出,强降雨一来修多少管道都不够用。正在试点的“海绵城市”并不是一座城,而是新一代城市雨洪管理概念,希望水渗下去,蓄起来,以适应环境变化和应对雨水带来的自然灾害。这就需要我们转变以往陈旧的城市建设理念,不再片面追求高楼大厦,而更加注重城市设计的精细化、人性化。

       材料二:“海绵城市”,顾名思义城市就像海绵一样,下雨时能够及时吸水、蓄水、渗水、净水,需要时将蓄存的水再释放出来,这样就需要有下沉式绿地、花园、可渗透路面这样的城市配套设施。然而,建设这些“海绵体”并不容易,资金需求巨大,无论是新城区建设还是老城区改造,始终绕不开“钱从哪儿来”的问题。而且熟悉这项技术的人才还相对缺乏,急需加大人才培养力度,为建设海绵城市提供充分的智力支持。

       材料三:中国城市规划设计研究院副院长邵益生认为,海绵城市建设不是一个部门一个单位就能完成的。国土、排水、道路、交通、园林……各个部门之间如何协调现在还在试点和探索中。

同类题5

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