Section outline

  • Stockcar race with multiple cars on a racetrack during a competitive event.

    In stockcar races, drivers often travel 500 miles or more, but their final displacement is only a few feet. Why?
    ::在储油罐的赛跑中,司机往往行驶500英里或500英里以上,但他们最后的流离失所只有几英尺。 为什么?

    Position, Distance, and Displacement
    ::职位、距离和流离失所

    In order to study how something moves, we must know where it is. This location is an object's position. To visualize position for objects moving in a straight line, you can imagine the object is on a number line. It may be placed at any point on the number line in the positive numbers or the negative numbers.  It is common to choose the original position of the object to be on the zero mark.  In making the zero mark the reference point, you have chosen a frame of reference.  The exact position of an object is the separation between the object and the reference point.
    ::为了研究某物如何移动,我们必须知道它的位置。 此位置是对象的位置。 要直线移动对象的可视位置, 您可以想象该对象在数字线上。 它可以在正数或负数的数字线的任何点上放置。 选择对象在零点上的原始位置是常见的。 在设定零点时, 您选择了一个参照框架。 对象的确切位置是对象和引用点之间的分隔 。

    When an object moves, we often refer to the amount it moves as the . Distance does not need a reference point and does not need a direction. If an automobile moves 50 kilometers, the distance traveled is 50 kilometers regardless of the starting point or the direction of movement. If we wish to find the final position of the automobile, however, just having the distance traveled will not allow us to determine the final position. We need to know the starting point and the direction of the motion. The change in the position of the object is called its displacement . The displacement must include a direction because the final position may be either in the positive or negative direction along the number line from the initial position.  The displacement is a vector quantity and are discussed in the chapter "Vectors".
    ::当一个物体移动时,我们常常提到它移动的数量。距离不需要参考点,也不需要方向。如果汽车移动50公里,行走距离为50公里,而不论起点或行走方向如何。如果我们想要找到汽车的最后位置,那么,只要行走距离将不允许我们确定最后位置。我们需要知道运动的起点和方向。物体位置的改变被称为转移。迁移必须包含一个方向,因为最终位置可能是沿着最初位置的数字线的正或负方向。迁移是一个矢量,在“导体”一章中讨论。

    To return to the first image, these cars travel a distance of 500 miles over the course of the race. However, they are traveling in a circle, and the start and finish line are the same. Therefore, when the car finishes the race, it is in essentially the same position it was when it started. The car's total displacement is only a few feet.
    ::回到第一张图象,这些汽车在赛道上行驶500英里。然而,它们环绕着一个圆圈行驶,起点和终点线相同。因此,当汽车完成赛事时,它的位置与比赛开始时基本相同。汽车的完全偏移只有几英尺。

    Use the following simulation to further explore the concepts of position, distance and displacement:
    ::利用下列模拟进一步探讨位置、距离和迁移的概念:

    Further Reading
    ::继续阅读

    Summary
    ::摘要

    • The length traveled by an object moving in any direction or even changing direction is called distance.
      ::向任何方向移动或甚至改变方向的物体所穿行的长度称为距离。
    • The location of an object in a frame of reference is called position.
      ::参照框架中对象的位置称为位置。
    • For straight line motion, positions can be shown using a number line.
      ::对于直线运动,可用数字线显示位置。
    • The separation between original and final position is called displacement.
      ::最初立场与最后立场的分离称为流离失所。

    Review
    ::回顾

    1. Explain the difference between distance and displacement in your own words.
      ::用您自己的语言解释距离和迁移之间的差别。
    2. Suppose that John lives on a square block that is 180 yards per side, and in the evenings, he walks with his dog around the block for a little exercise.
      1. If John walks once around the block, what distance does he travel?
        ::如果约翰在街上走过一圈 他走多远?
      2. If John walks once around the block, what is his final displacement?
        ::如果约翰在街上走过一次 他最后的流离失所是什么?

      ::假设约翰住在一面180码的方块上,晚上,他和他的狗在街区周围散步锻炼。如果约翰在街区周围走过一圈,他走的距离是多少?如果约翰在街区周围走过一圈,他最后的流离失所又是什么?
    3. Joanna's house is 8000 feet due west of her school. If her house is assigned the position of zero and her school is assigned the position of +8000, what would be Joanna's position if she walked 100 feet west of her house?
      ::乔安娜的家在8000英尺处,位于学校以西,如果她的房子被分配为零,学校被分配为+8000,那么如果乔安娜走在她家以西100英尺处,她的地位会如何?

    Explore More
    ::探索更多

    Watch these two short videos to understand position, distance, and displacement, and answer the questions below:
    ::观察这两段短片, 以了解位置、距离和流离失所, 并回答下列问题:

     

    1. What is position?
      ::什么是位置?
    2. Can two objects be the same distance from a single point but be in different positions? Why or why not?
      ::是否两个对象与一个点的距离相同,但位置不同?为什么或为什么没有?
    3. What is the difference between distance and displacement?
      ::距离和流离失所之间有什么区别?
    4. Does distance have direction? Does displacement have direction?
      ::距离有方向吗 流离失所有方向吗