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【简答题】

(18分)如图(a)所示,“ ”型木块放在光滑水平地面上,木块水平表面AB粗糙,光滑表面BC且与水平面夹角为θ=37°.木块右侧与竖直墙壁之间连接着一个力传感器,当力传感器受压时,其示数为正值;当力传感器被拉时,其示数为负值.一个可视为质点的滑块从C点由静止开始下滑,运动过程中,传感器记录到的力和时间的关系如图(b)所示.已知sin37°=0.6,cos37°=0.8,g取10m/s 2.求: (18分)如图(a)所示,“ ”型木块放在光滑水平地面上,木块水平表面AB粗糙,光滑表面BC且与水平面夹角为θ=37°.木块右侧与竖直墙壁之间连接着一个力传感器,当力传感器受压时,其示数为正值;当力传感器被拉时,其示数为负值.一个可视为质点的滑块从C点由静止开始下滑,运动过程中,传感器记录到的力和时间的关系如图(b)所示.已知sin37°=0.6,cos37°=0.8,g取10m/s 2.求: (1)斜面BC的长度; (2)滑块的质量; (3)运动过程中滑块克服摩擦力做的功

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【多选题】摩擦力有哪些( )

A.
滑动摩擦力
B.
滚动摩擦力
C.
弹性力
D.
静摩擦力

【单选题】螺纹联接中,属于附加摩擦力防松装置的是()。

A.
弹簧垫圈防松
B.
开口销与带槽螺母防松
C.
止动垫圈防松
D.
串联钢丝防松

【单选题】()产生的摩擦力最小。

A.
干摩擦
B.
液体摩擦
C.
半干摩擦
D.
半液体摩擦

【单选题】如图所示,斜面体放置在水平地面上,物块沿粗糙的斜面加速下滑,斜面体始终保持静止,在此过程中()。

A.
斜面体对物块的作用力斜向左上方
B.
斜面体对物块的作用力斜向右上方
C.
地面对斜面体的摩擦力为0
D.
地面对斜面体的支持力大于物块与斜面体的重力之和

【单选题】In the wake of 11 September, Visionics, a leading manufacturer, issued a fact sheet explaining how its technology could enhance airport security. They called it "protecting civilization from the faces...

A.
any way, the face-recognition technology is good enough to frighten the terrorists
B.
the industry will have to recognize the real situation and work hard to improve the technology
C.
all the claims are premature
D.
we must not expect too much

【单选题】Passage 4 In the wake of 11 September, Visionics, a leading manufacturer, issued a fact sheet explaining how its technology could enhance airport security. They called it "protecting civ...

A.
Too many false alarms were raised.
B.
Everyone should look straight at the camera.
C.
Only 90% of suspects at an airport were found.
D.
Everyone should not disguise himself.
相关题目:
【多选题】摩擦力有哪些( )
A.
滑动摩擦力
B.
滚动摩擦力
C.
弹性力
D.
静摩擦力
【单选题】螺纹防松装置中属摩擦力防松的是()。
A.
开口销与槽母
B.
止动垫
C.
粘接剂
D.
对顶螺母
【单选题】螺纹联接中,属于附加摩擦力防松装置的是()。
A.
弹簧垫圈防松
B.
开口销与带槽螺母防松
C.
止动垫圈防松
D.
串联钢丝防松
【单选题】()产生的摩擦力最小。
A.
干摩擦
B.
液体摩擦
C.
半干摩擦
D.
半液体摩擦
【单选题】如图所示,斜面体放置在水平地面上,物块沿粗糙的斜面加速下滑,斜面体始终保持静止,在此过程中()。
A.
斜面体对物块的作用力斜向左上方
B.
斜面体对物块的作用力斜向右上方
C.
地面对斜面体的摩擦力为0
D.
地面对斜面体的支持力大于物块与斜面体的重力之和
【单选题】In the wake of 11 September, Visionics, a leading manufacturer, issued a fact sheet explaining how its technology could enhance airport security. They called it "protecting civilization from the faces...
A.
any way, the face-recognition technology is good enough to frighten the terrorists
B.
the industry will have to recognize the real situation and work hard to improve the technology
C.
all the claims are premature
D.
we must not expect too much
【单选题】Passage 4 In the wake of 11 September, Visionics, a leading manufacturer, issued a fact sheet explaining how its technology could enhance airport security. They called it "protecting civ...
A.
Too many false alarms were raised.
B.
Everyone should look straight at the camera.
C.
Only 90% of suspects at an airport were found.
D.
Everyone should not disguise himself.