Name: tracking motion with position and displacement
Uploaded: 2023-09-22T11:49:39.000Z
Duration: 1 min 31 s
Channel: JoVE

为了描述物体的运动，需要相对于一个方便的参考系来确定其位置。用于描述物体位置和运动的一组任意坐标轴称为参考系。
通常，以地球或地球上的静止物体作为参考系。例如，飞机起飞过程中的位置可以用地球整体或机场塔台作为参考来描述。为了描述物体在一维运动中的位置，我们通常使用变量 x。
现在，假设一个物体相对于某个参考系发生运动——例如，一辆汽车相对于一栋建筑物向左移动，那么该汽车的位置就会发生变化。这种位置的变化称为位移。
然而，沿一条直线的 x 数值定义了物体可能所处的位置。沿此直线的任何位置变化均用位移表示，其中 Δx 为位移，其值通过用最终位置减去初始位置计算得出。位移是矢量，因其表示方向，且根据正方向的选择，其值可为正值或负值。

位置与位移

一个物体的位置定义了其在任何特定时间相对于一个便利的参考系的位置。 参考系是描述物体位置和运动的任意一组轴。 地球常被用作参考系，我们通常描述一个物体的位置时会参照地球上的静止物体。 例如，火箭发射可以用火箭相对于整个地球的位置来描述。 而骑自行车者的位置可以根据他们相对于他们经过的建筑物的位置来描述。 在其他情况下，我们使用的参考系不是静止的，而是相对于地球在运动。 例如，为了描述人在飞机上的位置，我们使用飞机而不是地球作为参考系。 对于一维运动的物体，我们经常使用x变量来描述其位置。 如果一个物体相对于参考系移动，则该物体的位置将随之变化。 例如，如果一位教授相对于白板向右移动，那么该教授的位置就发生了变化。 这种位置的变化称为位移。 位移一词表示物体已移动或已移位。 虽然位置是物体所在直线上的的一个 x 值，但位移则表示该物体在直线上的位置变化。 由于位移表示方向，因此位移是一个矢量，可以是正值，也可以是负值，具体取决于选择哪个方向为正值。 此外，运动分析可能涉及多个位移。 例如，如果选择右侧为正，物体向右移动 2 m，然后向左移动 4 m，则各个位移分别为 2 m 和±4 m。 位移用“x”表示，即位置的变化。 我们求位移时，总是用最终位置减去初始位置。 本文改编自 <a href="https://openstax.org/books/university-physics-volume-1/pages/3-1-position-displacement-and-average-velocity">Openstax， 大学物理第 1 卷第 3.1 节：位置、位移和平均速度</a>。

物体的位置是指其在任意特定时刻相对于一个方便的参考系的所在地点。参考系是人为设定的……

Education

教育

JoVE Core

Mechanical Engineering

机械工程

Unit 1

第一单元

Physics Basics

物理基础

KEY TERMS AND CONCEPTS

关键术语与概念

Position and Displacement

位置和位移

tracking motion with position and displacement

Position and displacement are key ideas in straight-line motion. Position tells where an object is located compared with a chosen starting point, called the origin. Displacement describes how far and in what direction the object has moved from its starting position.

These ideas help describe motion clearly. Position can change as an object moves. Displacement focuses on the change in position, not just the path taken. That makes it useful for comparing motion in a simple and precise way.

Tracking Motion with Position and Displacement

tracking-motion-with-position-and-displacement

introduction to scalers

Scalar Quantities in Physics

Scalar quantities in physics have size only. They do not include direction. This makes them different from vector quantities. Common scalar examples include mass, temperature, time, and energy. Each one can be described with a number and a unit. Because direction is not part of the value, scalars are often easier to compare and measure.

vector or cross product

Cross Product of Two Vectors

The cross product of two vectors gives a new vector that is related to both original vectors. It is also called the vector product. In many physics problems, this operation helps describe quantities that depend on direction as well as size. The result of a cross product has a direction set by the two input vectors. It is not the same as ordinary multiplication. The transcript focuses on the vector or cross product as a core vector operation students use when working with vectors in science.

introduction to vectors

Vectors in Motion and Direction

Vectors describe quantities that have both size and direction. They are used in physics to show how motion, force, and other quantities act in space. A vector can be represented with an arrow. The length of the arrow shows the size, and the arrowhead shows the direction. This makes vectors useful for comparing how one quantity points relative to another. Scalars are different because they have size only and no direction. Understanding the difference between vectors and scalars is an important...

units and standards of measurement

Measurement Units, Standards, and SI Basics

Measurement units, standards, and SI basics help scientists describe physical quantities clearly. A unit gives a number meaning, while a standard provides a fixed reference for that measurement. Together, they make results easier to compare and understand. The International System of Units, or SI, is the most common measurement system in science. It uses agreed-upon base units for common quantities. These standards reduce confusion when measurements are shared across labs, classrooms, and...

accuracy and precision

Measurement Errors, Accuracy, and Precision

Measurement errors can affect how close a result is to the true value and how consistent repeated results are. Accuracy describes how close a measurement is to the accepted or true value. Precision describes how close repeated measurements are to one another. A result can be accurate, precise, both, or neither. A set of measurements may cluster tightly together and still be far from the true value. Another set may include values spread out from one another, even if one of them is close to the...

rules of significant figures

Counting Significant Figures in Measurements

Significant figures help students record measurements with the correct level of precision. They show which digits in a number are meaningful and which only help place the decimal point. In science class, this idea matters when writing and comparing measured values. The rules for significant figures explain how to count these digits in different numbers. Some digits are always counted, while others depend on where they appear in the number. Learning the rules makes it easier to report answers...

random and systematic errors

Measuring Error in Scientific Data

Random and systematic errors affect scientific measurements. Random errors cause values to spread around the true value. They make repeated measurements less consistent. Systematic errors shift measurements in the same direction each time. Understanding both kinds of error helps students judge data quality. Random error can come from small changes during measurement. Systematic error can come from a biased tool or method. Scientists look for these patterns so they can improve results and...

position and displacement

Position and displacement are key ideas in straight-line motion. Position tells where an object is located compared with a chosen starting point, called the origin. Displacement describes how far and in what direction the object has moved from its starting position. These ideas help describe motion clearly. Position can change as an object moves. Displacement focuses on the change in position, not just the path taken. That makes it useful for comparing motion in a simple and precise way.

position and displacement vectors

Using Vectors to Describe Motion

Position and displacement vectors describe motion in physics. A position vector shows where an object is located relative to a chosen origin. A displacement vector shows how far and in what direction the object moves from one point to another. These vectors are useful because they give a clear way to track movement in space. The video connects position and displacement to the idea of a reference point and shows how direction matters as much as distance. That makes them important for describing...

mass and weight

How Mass Differs from Weight

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acceleration due to gravity on earth

Free-Fall Acceleration on Earth

Free-fall acceleration on Earth describes how fast an object speeds up when gravity is the only force acting on it. Near Earth’s surface, this acceleration is nearly constant for many everyday situations. Gravity pulls objects toward Earth and gives them downward acceleration. This motion is often written as g, and it helps explain why falling objects gain speed as they move downward. The value of g is commonly used in physics to predict the motion of objects dropped or released near the...

tension

Tension in Ropes and Strings

Tension is the pulling force carried by a rope, string, or cable when it is stretched by a load. In physics, this force acts along the length of the object and pulls away from the objects at each end. A stretched rope can support a hanging mass because the tension in the rope balances the weight of the load. The same idea appears in many everyday situations, such as a cable holding a sign or a string lifting an object. Understanding tension helps students connect force diagrams to real motion.

gravitational force

How Gravity Acts Between Objects

Gravity is a force that pulls objects toward one another. On Earth, this force gives objects weight and keeps people, water, and other materials from drifting away. It also helps explain why planets and moons stay in motion around larger bodies. The strength of gravitational force depends on the masses of the objects involved. Larger masses create a stronger pull, while smaller masses create a weaker one. The distance between objects also matters, because gravity becomes weaker as objects move...

key terms and concepts

Learn how position and displacement describe straight-line motion. Explore the origin, change in position, and direction in a clear high school science format.

Tracking Motion with Position and Displacement | JoVE K12

JoVE Core Mechanical Engineering offers concise, easy-to-understand animated videos covering key topics such as equilibrium, forces, truss analysis, and structural mechanics. Explore their real-world applications, and witness these concepts in action through scientist-led experiments.

mechanical engineering

Tracking Motion with Position and Displacement

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