章节大纲

  • An old chimney with a spiral staircase wrapped around it, illustrating a screw mechanism.

    This old chimney has a spiral staircase wrapped around it. The spiral staircase contains an , or ramp. Do you see it? The stairs that wrap around the outside wall of the chimney make up the inclined plane. Together with the chimney, they represent a called a screw.
    ::这个老烟囱有一个螺旋楼梯环绕着它。 螺旋楼梯包含一个或斜坡。 你看到了吗? 环绕烟囱外墙的楼梯组成了倾斜的平面。 它们与烟囱一起代表了一个叫做螺丝的螺丝。

    What Is A Screw?
    ::什么是螺丝?

    A screw is a simple machine that consists of an inclined plane wrapped around a central cylinder. No doubt you are familiar with screws like the wood screw in the left-hand side of the Figure . The cap of the bottle pictured on the right is another example of a screw. Screws move objects to a greater depth (or higher elevation) by increasing the force applied to the screw. Many screws are used to hold things together, such as two pieces of wood or a screw cap and bottle. When you use a screw, you apply force to turn the inclined plane. The screw, in turn, applies greater force to the object, such as the wood or bottle top. 
    ::螺丝是一种简单的机器,由环绕中央圆柱的倾斜平面组成。 毫无疑问, 您熟悉像图左侧的木螺一样的螺丝。 右边描绘的瓶盖是螺丝的另一个例子。 螺丝将物体移动到更大的深度( 或更高的高度) , 增加螺丝的强度 。 许多螺丝被用来把东西固定在一起, 如两块木头或螺丝帽和瓶子。 当您使用螺丝时, 您会用武力来转换倾斜的平面 。 螺丝反过来又对物体施加更大的力, 如木头或瓶顶 。

    A wood screw on the left and a bottle cap on the right, both illustrating screws.

    Q : Can you identify the inclined plane in each example of a screw pictured in the Figure ?
    ::问题:您能否在图中描绘的螺丝的每个例子中辨别倾斜平面 ?

    A : The inclined plane of the screw on the left consists of the ridges, or threads, that wrap around the central cylinder of the screw. The inclined plane of the cap on the right consists of the ridges that wrap around the inner sides of the cap.
    ::A: 螺旋左侧的倾斜平面由环绕螺旋中央圆柱的脊或线组成。 右侧的顶部倾斜平面由环绕顶内侧的脊组成。

    Mechanical Advantage Of A Screw
    ::A螺旋的机械优势

    The of a simple machine is the factor by which it multiplies the force applied to the machine. It is the ratio of the output force to the input force. The force applied by the screw (output force) is always greater than the force applied to the screw (input force). Therefore, the mechanical advantage of a screw is always greater than 1.
    ::简单的机器是它乘以机器所用力的因素。它是输出力与输入力之比。螺丝(输出力)所施力总是大于螺丝(输入力)所施力。因此螺丝的机械优势总是大于1。

    Look at the two screws in the Figure . In the screw on the right, the threads of the inclined plane are closer together. This screw has a greater mechanical advantage and is easier to turn than the screw on the left, so it takes less force to penetrate the wood with the right screw. The trade-off is that more turns of the screw are needed to do the job because the over which the input force must be applied is greater.
    ::看看图中的两个螺丝。在右边的螺丝中,倾斜平面的线线更加接近。这个螺丝的机械优势更大,比左侧的螺丝更容易转弯,因此用右螺丝穿透木头的力度要小一些。 权衡是,需要螺丝更多的转弯来完成这项工作,因为输入力必须应用的弯曲更大。

    Two screws with different thread spacing demonstrating mechanical advantage in wood penetration.

    Q : Why is it harder to turn a screw with more widely spaced threads?
    ::问:为什么更难用更宽空格的线来改变螺丝?

    A : The screw moves farther with each turn when the threads are more widely space, so more force must be applied to turn the screw and cover the greater distance.
    ::A:当线条空间更加宽广时,螺丝会随每个转弯而移动更远,所以必须用更多的力来扭转螺丝并覆盖更大的距离。

    Summary
    ::摘要

    • A screw is a simple machine that consists of an inclined plane wrapped around a central cylinder. Screws move objects to a greater depth (or higher elevation) by increasing the force applied to the screw.
      ::螺丝是一种简单的机器,由环绕中央圆柱的倾斜平面组成。螺丝将物体移动到更深(或更高高)的地方,增加螺丝的强度。
    • The mechanical advantage of a screw is always greater than 1 because the output force applied by the screw is greater than the input force applied to the screw.
      ::螺丝的机械优势总是大于1,因为螺丝的输出力大于螺丝的输入力。

    Review
    ::回顾

    1. What is a screw?
      ::什么是螺丝?
    2. How are screws used?
      ::螺丝如何使用?
    3. Give an example of a screw that is not mentioned in the article.
      ::举一例说明该条中没有提到的螺丝。
    4. Why is the mechanical advantage of a screw always greater than 1? 
      ::为什么螺丝的机械优势总是大于1?