摩擦力

什么是摩擦力？

What is the meant by frictional force?

• 一种力涉及阻碍物体的移动

  An effort to resist movement

• 一种力涉及改变物体

  A force to change an object

• 一种力涉及当两个物体的表面互相接触时所产生的阻碍物体移动

  The force produced when two surfaces are in contact with each other

• 推力和拉力施加在物体上

  Pulling and pushing that is applied on an object

下列哪项是说明摩擦力的例子？

Which of the following examples explains the meaning of frictional force?

• 铝罐被挤压后而变成扁铝罐

  An aluminium can is dented after being squeezed

• 自行车的踩踏板被踏得很快

  A pedaled bicycle moves faster

• 一个盒子在草地上被拉着很难移动

  A box that is pushed on the grass is difficult to move

• 一个球当被踢时而改变移动的方向

  A rolling ball changes its direction when kicked

哪项不是影响摩擦力的因素？

Which of the following do not affect the frictional force?

• 物体的形状 The shape of object

• 物体的质量 The mass of object

• 粗糙的表面 The roughness of surface

• 干的表面 The dry of surface

一组学生在进行实验。 他们在四种不同表面上滚动玻璃弹珠。 图上显示实验的结果。

A group of pupils carried out an investigation by rolling a marble on four different surfaces. Diagram above shew the results of the investigation.

哪项是 表面 R, S 和 T ？

What surfaces are R, S and T ?

• R - 马尼拉卡Manila card S - 砂纸 Sandpaper

  T - 玻璃Glass

• R - 砂纸 Sandpaper S - 马尼拉卡Manila card

  T - 玻璃Glass

• R - 砂纸 Sandpaper S - 玻璃 Glass

  T - 马尼拉卡 Manila card

• R - 玻璃 Glass S - 砂纸 Sandpaper

  T - 马尼拉卡 Manila card

实验里， 一辆玩具车在不同的表面上行走。 哪一种表面能使玩具车停止最慢？

In an investigation , a toy car is pushed on different surfaces. Which surface causes the toy car to stop the latest?

• 玻璃表面 Glass surface

• 石灰表面 Cement surface

• 草地表面 Grass surface

• 地毯表面 Carpeted surface

物体的表面越 ， 所产生的摩擦力越 。

A surface produces frictional force

• 粗糙 rough , 小 less

• 粗糙 rough , 大 more

• 光滑 smooth, 大 more

• 光滑 smooth , 没有 non

哪项活动显示摩擦力的益处？

Which of the following activities shows an advantages of frictional force?

• 鞋子底部的纹路磨损 Wearing out the tread on shoe soles

• 磨刀 Sharpening a knife

• 使物体难以移动 Slowing down movements

• 笔尖变钝 Making a pencil blunt

上图显示门的合页

Diagram above shows a door hinge.

下列哪项可以帮们的合页减少摩擦力？

Which of the following can reduce the friction at the door hinge?

• 水 water

• 轮子 Wheel

• 润滑油 Oil

• 爽身粉 Talcum powder

图上显示工人在推盒子而面对困难。

Diagram above shows a worker is having a problem in pushing a box.

下列哪项说明是最容易的方法来推动盒子？

Which of the following is the easiest way to push the box?

• 用绳子来拉动盒子

  Pull the box by using a string

• 撒一些沙在地上的表面

  Scatter some sand on the surface of the floor

• 撒一些盐在地上的表面

  Scatter some salt on the surface of the floor

• 放滚杠在盒子下面

  Put the rollers under the box

应用以下哪种物体可以增加摩擦力？

• 气垫

• 润滑油

• 光滑的表面

• 有花纹的表面