Name: negative acceleration and motion reversal
Uploaded: 2023-04-30T10:51:51.000Z
Duration: 1 min 10 s
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

Direction of Acceleration Vectors

Lorsqu’un objet se déplace à une vitesse constante sur une trajectoire en ligne droite, il n’est pas impliqué dans un mouvement accéléré. Au lieu de cela, il accélère soit en accélérant, soit en ralentissant.
Cependant, sur une trajectoire courbe, même à vitesse constante, le mouvement de l'objet est toujours accéléré car sa direction de mouvement change continuellement. Par conséquent, l’accélération existe lorsqu’il y a un changement de vitesse, qui peut être dû soit à un changement de vitesse, soit à un changement de direction, soit aux deux simultanément.
Pour un objet se déplaçant le long d’une trajectoire courbe à vitesse constante, la direction du vecteur accélération est vers le centre de la courbure de la trajectoire.
Lorsque l’objet accélère, le vecteur d’accélération pointe devant le centre de la courbure. Lors du ralentissement, l’accélération pointe derrière le centre de la courbure. Lorsque l’objet se déplace en ligne droite, l’accélération se fait le long de la trajectoire.

direction des vecteurs d'accélération

L'accélération se produit lorsque la vélocité change en magnitude (une augmentation ou une diminution de la vitesse), en direction ou les deux. Bien que l'accélération soit dans la direction du changement de vélocité, ce n'est pas toujours dans la direction du mouvement. Lorsqu'un objet ralentit, son accélération est opposée à la direction de son mouvement. On l'appelle souvent décélération. Cependant, le terme décélération peut causer de la confusion dans l'analyse car ce n'est pas un vecteur ; il ne pointe pas dans une direction spécifique par rapport à un système de coordonnées, il doit donc y avoir un signe approprié pour la valeur de la décélération dans le système de coordonnées choisi. Si l'accélération d'un objet est dans la direction négative dans le système de coordonnées choisi, on dit que l'objet subit une accélération négative.

Imaginez un objet en mouvement ayant une vélocité dans la direction positive par rapport à un origine choisie, et qu'il acquiet une accélération négative constante. Dans ce cas, l'objet finit par s'arrêter et inverse sa direction. Après un certain temps, l'objet passe par l'origine et se dirige vers la direction opposée.

Ce texte est adapté de <a href="https://openstax.org/books/university-physics-volume-1/pages/4-2-acceleration-vector">Openstax, University Physics Volume 1, Section 4.2: Acceleration Vectors.</a>

Direction des vecteurs d'accélération

L’accélération se produit lorsque la vitesse change d’amplitude (une augmentation ou une diminution de la vitesse), de direction ou des deux. Bien que l’accélération soit dans le sens ...

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

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 sign must be used in the chosen coordinate system.

If an object has acceleration in the negative direction of the coordinate system, it is undergoing negative acceleration. For example, an object can move in the positive direction at first and still have a constant negative acceleration. In that case, it will slow to a stop and then reverse direction.

After some time, the object can pass through the origin while moving in the opposite direction. This shows how the sign of acceleration and the direction of motion can differ. Understanding this idea helps with motion analysis in one-dimensional physics.

Negative Acceleration and Motion Reversal

negative-acceleration-and-motion-reversal

position and displacement vectors

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...

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

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 acceleration can point opposite motion, why deceleration can be confusing, and how negative acceleration can stop and reverse an object.

Negative Acceleration and Motion Reversal | 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

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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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Average Acceleration

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Instantaneous Acceleration

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Position and Displacement Vectors

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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Acceleration Vectors

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Linear Momentum

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Electrical Current

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PS.PSc.6.2

Continuity Equation

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Boundary Conditions for Current Density

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Electrical Conductivity

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Theory of Metallic Conduction

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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

Magnets are commonly found in everyday objects, such as toys, hangers, elevators, doorbells, and computer devices. Experimentation on these magnets shows ...

Magnetic Fields

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Magnetic Field Lines

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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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The Hall Effect

Edwin H. Hall, in the year 1879, devised an experiment that could be used to identify the polarity of the predominant charge carriers in a conducting ...

Magnetic Field due to Moving Charges

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Consider a point charge moving with a ...

Biot-Savart Law

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Magnetic Field Of A Current Loop

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Solenoids

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Magnetic Field of a Solenoid

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Toroids

A toroid is a closely wound donut-shaped coil constructed using a single&#xA0; conducting wire. In general, it is assumed that a toriod consists of ...

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.

Negative Acceleration and Motion Reversal

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