Name: describing motion with position changes
Uploaded: 2023-04-30T10:51:28.000Z
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Channel: JoVE

K12 Standards

north-carolina-k-12-science-standard-course-of-study

North Carolina K-12 Science Standard Course of Study

9-12

Physical Science

motion-and-stability-forces-and-interactions

Motion and Stability- Forces and Interactions

PS.PSc.4.1

Position and Displacement Vectors

Considérez une mouche en mouvement. Pour localiser sa position dans un espace tridimensionnel, un système de coordonnées cartésiennes est utilisé, et les vecteurs unitaires le long de l’axe fournissent sa direction.
La flèche vectorielle qui s'étend de l'origine à l'emplacement de l'objet est le vecteur de position. Il peut être représenté en termes de vecteurs unitaires.
Le vecteur position est la somme des composantes vectorielles sur chaque axe et leurs normes fournissent la position le long de chaque axe.
Si la mouche continue son mouvement, son vecteur de position change, et la différence de vecteur entre les vecteurs de position est appelée le vecteur de déplacement, Δr, qui représente le changement de position.
Par exemple, si la mouche est au point A, et qu’après le temps t, elle atteint le point B, alors en utilisant les vecteurs position de A et B, le vecteur de déplacement de la mouche pour le temps t peut être obtenu.

vecteurs de position et de déplacement

Pour décrire le mouvement d'un objet, il faut d'abord être capable de décrire sa position (c’est-à-dire là où il se trouve à un moment donné). Plus précisément, la position doit être spécifiée par rapport à un cadre de référence pratique. Un cadre de référence est un ensemble arbitraire d'axes à partir desquels la position et le mouvement d'un objet sont décrits. La Terre est souvent utilisée comme cadre de référence pour décrire la position d'un objet par rapport aux objets stationnaires sur Terre.

De plus, plusieurs types importants de mouvement se déroulent uniquement dans deux dimensions, c'est-à-dire dans un plan. Ces mouvements peuvent être décrits par deux composantes de position, de vélocité et d'accélération. Si un objet se déplace par rapport à un cadre de référence, alors la position de l'objet change ; ce changement de position est appelé déplacement. Le mot déplacement implique qu'un objet a bougé ou a été déplacé. Étant donné que le déplacement indique une direction, il s'agit d'un vecteur et peut être soit positif, soit négatif, en fonction du choix de la direction. De plus, une analyse du mouvement peut comporter de nombreux déplacements incorporés, et de nombreuses applications en physique peuvent comporter une série de déplacements. Ainsi, le déplacement total est la somme des déplacements individuels, qui doivent être évalués avec soin en utilisant l'addition vectorielle.

Ce texte est adapté de <a href="https://openstax.org/books/university-physics-volume-1/pages/4-1-displacement-and-velocity-vectors">Openstax, University Physics Volume 1, Section 4:1 Displacement and Velocity Vectors.</a>

Vecteurs de position et de déplacement

Pour décrire le mouvement d’un objet, il faut d’abord être capable de décrire sa position (où il se trouve à un moment donné). Plus précisément, la position ...

Education

Enseignement

JoVE Core

Physics

Physique

Unit 1

Unité 1

Motion in Two or Three Dimensions

Mouvement en deux ou trois dimensions

KEY TERMS AND CONCEPTS

TERMES ET CONCEPTS CLÉS

describing motion with position changes

Describing motion starts with position. Position tells where an object is at a particular time. It must be measured relative to a frame of reference, which is an arbitrary set of axes used to describe position and motion.

Earth is often used as a frame of reference. It helps describe an object’s location in relation to stationary objects on Earth. Many important motions also take place in two dimensions, or in a plane. In those cases, position, velocity, and acceleration can each be described with two components.

When an object moves relative to a frame of reference, its position changes. This change in position is called displacement. Displacement shows direction, so it is a vector. Depending on the chosen direction, it can be positive or negative.

Motion can include many separate displacements. In many physics problems, these displacements are combined into a total displacement. The total displacement is the sum of the individual displacements, and it should be found carefully using vector addition.

Describing Motion with Position Changes

position and displacement vectors

Describing motion starts with position. Position tells where an object is at a particular time. It must be measured relative to a frame of reference, which is an arbitrary set of axes used to describe position and motion. Earth is often used as a frame of reference. It helps describe an object’s location in relation to stationary objects on Earth. Many important motions also take place in two dimensions, or in a plane. In those cases, position, velocity, and acceleration can each be described...

average and instantaneous velocity vectors

average-and-instantaneous-velocity-vectors

Position Change and Instant Velocity

Position change and instant velocity are key ideas in kinematics. To describe motion, time must be included. Time tells us where an object is and how fast it is moving. The speed of an object comes from how its position changes with time. Each position is tied to a specific time. When the details of motion at each instant are not important, the rate is given as average velocity. Average velocity is a vector. It equals the total displacement between two points divided by the elapsed time. Real...

acceleration vectors

How Velocity Changes Create Acceleration

Acceleration describes how velocity changes over time. In physics, acceleration is a vector, which means it has both size and direction. It points in the same direction as the change in velocity, written as Δv. The larger the acceleration, the larger the change in velocity over a given time. Because velocity is a vector, it can change in more than one way. An object can speed up, slow down, change direction, or do both at once. A runner traveling 10 km/h due east who stops, turns around, and...

direction of acceleration vectors

Negative Acceleration and Motion Reversal

Acceleration describes a change in velocity. That change can be a change in speed, a change in direction, or both. The acceleration vector points in the direction of the velocity change, not always in the direction the object is moving. When an object slows down, its acceleration points opposite to its motion. This is often called deceleration. The term can be confusing in physics because deceleration is not a vector. It does not give a direction relative to a coordinate system, so the correct...

projectile motion

Projectile Paths Under Gravity

Projectile motion describes the path of an object thrown into the air under Earth’s gravity. The object is called a projectile, and its curved path is called the trajectory. This motion appears in many real situations, such as fireworks, a golf ball in flight, meteors entering Earth’s atmosphere, and bullets being fired. When a falling object has no horizontal movement, it is described as one-dimensional projectile motion. When motion includes both horizontal and vertical parts, it is...

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projectile motion: equations

Solving Projectile Motion with Components

Projectile motion can be solved by breaking the motion into horizontal and vertical components. This approach is used for common examples like a basketball throw, an arrow shot from a bow, and kids jumping into a pool. The motion is then analyzed along the x-axis and y-axis. Start by separating displacement into x and y parts. The horizontal and vertical parts of velocity are also separated. If the projectile has speed v and direction θ relative to the horizontal, the vertical component is...

projectile motion: example

Projectile Motion in Sports and Orbit

Projectile motion helps explain both sports throws and motion near Earth. A javelin thrower uses this idea to send the javelin as far as possible. The thrower also takes a short run-up to increase the initial speed of the javelin. For a projectile on level ground, the range is the horizontal distance it travels. The range is largest at a 45° angle, so javelin throwers try to release the javelin as close to that angle as possible. In this case, the range equation assumes the distance is very...

uniform circular motion

Centripetal Acceleration in Circular Motion

Uniform circular motion describes motion in a circle at constant speed. An object follows a curved path, but its speed does not change. The motion of a point on a propeller spinning at a steady rate and the second, minute, and hour hands of a watch are common examples. Even with constant speed, these objects are still accelerating. That idea can seem surprising because in one-dimensional motion, constant speed means zero acceleration. In two- and three-dimensional motion, a particle can...

non-uniform circular motion

Circular Motion with Changing Speed

Circular motion can happen with changing speed. In this case, the object still follows a circular path, but it may speed up or slow down as it moves. When speed changes during circular motion, the motion is called non-uniform circular motion. This adds tangential acceleration, which points along the path of motion and shows a change in speed. Centripetal acceleration is still present in circular motion. It describes the time rate of change of the direction of the velocity vector and points...

relative velocity in one dimension

Relative Motion in a Train and Earth

Relative motion depends on the reference frame used to measure velocity. A reference frame is the point of view from which motion is described. In many examples, Earth is the reference frame. If someone is said to be sitting in a train moving east at 10 m/s, that speed is measured relative to Earth.

relative velocity in two dimensions

Adding Velocities Across Reference Frames

Relative velocity describes motion as measured from a chosen reference frame. It can also describe the motion of one reference frame compared with another. In two dimensions, this idea helps track how position and velocity change from frame to frame. Consider a particle P and two reference frames, S and S′. The position of the origin of S′, measured in S, and the position of P, measured in S′, can be combined with vector addition to find the position of P in S. This relation shows how motion...

key terms and concepts

Learn how position, frame of reference, and displacement help describe motion in one or two dimensions, including vector addition and total displacement.

Describing Motion with Position Changes | JoVE K12

physics

JoVE Core Physique présente plusieurs branches de la physique fondamentale grâce à des vidéos animées concises et faciles à comprendre ; cela inclut: la cinématique, la dynamique, la mécanique des fluides, la mécanique statique, les ondes et l'acoustique. En parallèle, les vidéos de scientifiques à l'action démontrent l'application de concepts associés à ces domaines dans des expériences de recherche classiques et originales réalisées dans des laboratoires modernes du monde entier.

PS.Phy.1.2

ohios-learning-standards-and-model-curriculum

Ohio’s Learning Standards and Model Curriculum

Forces And Motion

Motion

Motion Graphs

Virginia  Standards of Learning

HIgh School

PS.8

PS.8.a

PH.2

PH.2.a

PH.2.c

Texas Essential Knowledge and Skills

High School

PHYS.5

PHYS.5.D

Arizona Science Standards

HS+Phy.P3

HS+Phy.P3U1.3

Alabama Course of Study Science

Motion and Stability: Forces and Interactions

9-12.P.1.1

9-12.P.1.1.c

Florida Department of Education

SC.912.P.12

SC.912.P.12.2

Georgia Standards of Excellence

SPS8.

Describing Motion

SP1.

Two-Dimensional Motion

Position and Displacement

The position of an object defines its location relative to a convenient frame of reference at any particular time. A frame of reference is an arbitrary ...

Average Velocity

To calculate the other physical quantities in kinematics, we must introduce the time variable. The time variable allows us not only to state the position ...

Instantaneous Velocity - I

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Instantaneous Velocity - II

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To describe the motion of an object, one should first be able to describe its position (where it is at any particular time). More precisely, the position ...

Average and Instantaneous Velocity Vectors

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PS.PSc.6.2

Continuity Equation

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Obtain, evaluate, and communicate information to explain how current is affected by changes in composition, length, temperature, and diameter of wire.

PS.PSc.6.3

Magnetism

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Magnetic Flux

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motion-of-a-charged-particle-in-a-magnetic-field

Motion Of A Charged Particle In A Magnetic Field

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Magnetic Force

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magnetic-force-on-a-current-carrying-conductor

Magnetic Force On A Current-Carrying Conductor

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magnetic-force-on-current-carrying-wires-example

Magnetic Force On Current-Carrying Wires: Example

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force-on-a-current-loop-in-a-magnetic-field

Force On A Current Loop In A Magnetic Field

Magnetic forces on wires carrying current are most frequently applied in motors. A DC motor is a device that converts electrical energy into mechanical ...

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Torque On A Current Loop In A Magnetic Field

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Toroids

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Use models to explain magnetism in terms of domains, interactions of poles, and magnetic fields.

PS.PSc.6.4

Analyze motion in terms of speed, velocity, acceleration, and momentum.

Describing Motion with Position Changes

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