Name: average acceleration and velocity change
Uploaded: 2023-04-30T10:50:13.000Z
Duration: 1 min 30 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

Average Acceleration

L’accélération est définie comme la variation de la vitesse avec le temps. Il s’agit d’une grandeur vectorielle qui implique un changement de magnitude ou de direction ou les deux.
Par exemple, une femme marche à 5 km/h vers l’est. Elle s’arrête et revient, marchant à 5 km/h vers l’ouest. Ici, la vitesse de la femme a changé en raison d'un changement de direction, bien que son amplitude soit la même dans les deux sens, ce qui a entraîné une accélération.
L’accélération est exprimée en mètres par seconde au carré et peut être interprétée à partir du graphique du vecteur vitesse en fonction du temps où le vecteur vitesse est sur l’axe des y et le temps est sur l’axe des x.
Par exemple, une femme marche sur une route. Au point P1, elle a une vitesse de v1x au temps t1. Et après un certain temps à t2, son vecteur vitesse est v2x au point P2. La variation de sa vitesse est donnée par Δv dans un intervalle de temps de Δt.
Ainsi, l’accélération moyenne de la femme se déplaçant du point P1 à P2 est la variation de la composante x de la vitesse, divisée par l’intervalle de temps. Il est également donné par la pente de la droite P1P2.

accélération moyenne

L'importance de comprendre l'accélération s'étend à nos expériences quotidiennes, ainsi qu'aux vastes étendues de l'espace extra-atmosphérique et au monde minuscule de la physique subatomique. Dans le langage courant, accélérer signifie augmenter la vitesse. Par exemple, nous sommes familiers avec l'accélération de notre voiture ; plus nous appuyons fort sur la pédale d'accélérateur, plus nous accélérons. Plus l'accélération est grande, plus le changement de vitesse est important sur une période donnée. L'accélération est largement observée en physique expérimentale. Dans les expériences du grand accélérateur de particules, par exemple, les particules subatomiques sont accélérées à des vitesses très élevées lors d'expériences de collision, ce qui nous renseigne sur la structure du monde subatomique ainsi que sur l'origine de l'univers. Dans l'espace, les rayons cosmiques sont des particules subatomiques qui ont été accélérées à des énergies très élevées dans les supernovas (explosions d'étoiles massives) et les noyaux actifs de galaxies. Il est important de comprendre les processus qui accélèrent les rayons cosmiques, car ces rayons contiennent un rayonnement très pénétrant qui peut par exemple endommager les équipements électroniques des engins spatiaux.

L'accélération moyenne est le taux de variation de la vitesse. Rappelons que la vitesse est un vecteur - elle a à la fois une magnitude et une direction - ce qui signifie qu'un changement de vitesse peut être un changement de magnitude (vitesse) ou un changement de direction. Par exemple, si un coureur se déplace à 10 km/h vers l'est, ralentit jusqu'à s'arrêter, change de direction et continue sa course à 10 km/h vers l'ouest, sa vitesse a changé en raison du changement de direction, même si la magnitude de la vitesse est la même dans les deux directions. Ainsi, l'accélération se produit lorsque la vitesse change en magnitude (augmentation ou diminution de la vitesse) ou en direction, ou les deux.

Ce texte est adapté de <a href="https://openstax.org/books/university-physics-volume-1/pages/3-3-average-and-instantaneous-acceleration">Openstax, University Physics Volume 1, Section 3.3: Average and Instantaneous Acceleration.</a>

Accélération moyenne

L’importance de comprendre l’accélération s’étend à nos expériences quotidiennes, ainsi qu’aux vastes étendues de l’espace extra-atmosphérique et au monde minuscule ...

Education

Enseignement

JoVE Core

Physics

Physique

Unit 1

Unité 1

Motion Along a Straight Line

Mouvement rectiligne

KEY TERMS AND CONCEPTS

TERMES ET CONCEPTS CLÉS

average acceleration and velocity change

Average acceleration describes how velocity changes over time. In physics, acceleration is not just about speeding up. It also includes slowing down and changing direction. Since velocity is a vector, it has both magnitude and direction.

A change in velocity can come from a change in speed, a change in direction, or both. For example, a runner may travel at 10 km/h due east, stop, reverse direction, and then continue at 10 km/h due west. Even though the speed is the same, the velocity has changed because the direction is different. That change in velocity means there is acceleration.

This idea appears in many settings. In everyday life, it helps explain a car’s motion when the driver presses harder on the gas pedal. In experimental physics, linear particle accelerator experiments use acceleration to push subatomic particles to very high velocities for collision studies. Those experiments help scientists learn about the structure of the subatomic world and the origin of the universe.

Acceleration also matters in space. Cosmic rays are subatomic particles that have been accelerated to very high energies in supernovas and active galactic nuclei. Studying how these rays are accelerated is important because they carry highly penetrating radiation. That radiation can damage electronics on spacecraft.

Average Acceleration and Velocity Change

position and displacement

Reference Frames and Motion in a Line

Position in straight-line motion depends on a frame of reference. A frame of reference is an arbitrary set of axes used to describe an object’s position and motion. It gives meaning to where something is located at a particular time. Earth is often used as the reference frame. In that case, we describe an object’s position relative to stationary objects on Earth. A rocket launch can be described this way. A cyclist’s position can also be described relative to the buildings they pass. <br...

average velocity

Average Velocity and Average Speed

Average velocity and average speed help describe motion in kinematics. To compare motion over time, we use the time variable. Time lets us track an object’s position and how fast that position changes. For motion between two points, each position x_i is paired with a time t_i. When the details of motion at each instant are not important, we use average velocity. Average velocity is a vector quantity, so it includes direction. It is found by dividing total displacement, Δx, by the time...

instantaneous velocity - i

Instantaneous Speed and Direction

Instantaneous velocity describes how fast an object is moving at a specific instant. It gives the motion of a particle at one point in time or at one point along its path. Average velocity over a time interval cannot show this level of detail. Instantaneous velocity, often written as v x , is the limit of average velocity as the elapsed time approaches zero. It can also be found as the derivative of x with respect to t . Like average velocity, it is a vector with dimensions of length per unit...

instantaneous velocity - ii

Instantaneous Velocity from Position Graphs

Instantaneous velocity describes how fast an object is moving at a specific moment along its path. It is the limit of average velocity as the elapsed time approaches zero. It can also be written as the derivative of displacement with respect to time. Like average velocity, instantaneous velocity is a vector, so it has both size and direction. Its units are length per unit time. Instantaneous velocity can be positive or negative. A position-time graph can show it at any point on the motion...

average acceleration

Average acceleration describes how velocity changes over time. In physics, acceleration is not just about speeding up. It also includes slowing down and changing direction. Since velocity is a vector, it has both magnitude and direction. A change in velocity can come from a change in speed, a change in direction, or both. For example, a runner may travel at 10 km/h due east, stop, reverse direction, and then continue at 10 km/h due west. Even though the speed is the same, the velocity has...

instantaneous acceleration

Negative Acceleration and Instant Speed Change

Acceleration shows how velocity changes, and it does not always point in the same direction as motion. When an object slows down, its acceleration points opposite to its motion. This is often called deceleration, but that term can cause confusion because deceleration is not a vector and does not point in a specific direction in a coordinate system. A subway train is a simple example. When the train slows down, it is still accelerating, but the acceleration points opposite to the direction it...

kinematic equations - i

Velocity from Constant Acceleration

Velocity from constant acceleration shows how an object’s speed and direction change when the acceleration stays the same. The first kinematic equation connects initial velocity, acceleration, and time for motion with constant acceleration. It helps describe how velocity changes at a steady rate throughout the motion. The equation matches common sense in several cases. If acceleration is zero, the final velocity is the same as the initial velocity, so the object keeps a constant velocity. If...

kinematic equations - ii

Using the Second Kinematic Equation

The second kinematic equation relates an object’s final position to its initial position, its starting velocity, and the extra distance gained as velocity changes. It is used only when acceleration stays constant during the motion. That makes it useful for straight-line motion problems with a steady rate of acceleration. A car merging onto a 200 m freeway ramp is a good example. In the example, the car starts at 10 m/s and accelerates at 2 m/s². The known values are the distance, the initial...

kinematic equations - iii

Constant-Acceleration Kinematics Formulas

Constant-acceleration kinematics formulas connect an object’s motion when acceleration stays the same. They help describe how velocity and position change over time. These equations are useful for solving motion problems and for understanding the relationships among distance, time, velocity, and acceleration. The third kinematic equation does not use time as a variable. Instead, it gives final velocity in terms of acceleration and the distance over which that acceleration acts. The fourth...

kinematic equations: problem solving

Solving Constant Acceleration Motion Problems

Solving one-dimensional motion problems with constant acceleration starts with identifying the known quantities and choosing the right kinematic equation. A kinematic equation is a motion formula that relates displacement, velocity, acceleration, and time. Depending on what is known and unknown, you may need one equation or two equations to find the answer. In many problems, the number of equations needed matches the number of unknowns. Two-body pursuit problems are different. They always...

free-falling bodies: introduction

Gravity and Free-Fall Motion

Gravity and free-fall motion explain how objects move when only Earth’s gravity acts on them. In free-fall, the motion is caused by gravitational force, and air resistance is neglected. This means the object accelerates toward Earth’s center. This result is surprising because everyday experience includes friction and air resistance. We often expect lighter objects to fall more slowly than heavier ones. People held that idea until Galileo Galilei proved that mass does not change the...

free-falling bodies: example

Gravity-Driven Free Fall Motion

Gravity-driven free fall motion is the motion of an object when gravity is the only force acting on it and air resistance is absent. In this case, the object is in free-fall. The acceleration due to gravity stays constant, no matter how much the object weighs. Free-fall is not limited to objects moving straight down. It also includes motion that is affected only by gravity. Because the acceleration is constant, the motion can be described with kinematic equations. Objects dropped from the...

velocity and position by graphical method

velocity-and-position-by-graphical-method

Acceleration Graphs for Motion Prediction

Acceleration graphs can be used to find velocity and position over time. The area under an acceleration-time graph gives the change in velocity. The area under a velocity-time graph gives the change in position, or displacement. A real example is an airplane using an inertial navigation system. Before takeoff, the pilot enters the airplane’s initial position and velocity. The system then uses acceleration data to calculate the airplane’s velocity and position during flight. When acceleration...

velocity and position by integral method

Finding Motion from Acceleration Data

Velocity and position can be found from acceleration using integral calculus. When acceleration is known as a function of time, the velocity function comes from integrating acceleration. The position function then comes from integrating velocity. For constant acceleration, these integral steps match the first and second kinematic equations for velocity and position. The example in this lesson uses a motorboat that is moving at 5.0 m/s and then begins to slow down as it approaches the dock. Its...

key terms and concepts

Explore average acceleration, velocity as a vector, and how changes in speed or direction create acceleration in cars, runners, particle beams, and cosmic rays.

Average Acceleration and Velocity Change | 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.1.1

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Ohio’s Learning Standards and Model Curriculum

Forces And Motion

Motion

Virginia  Standards of Learning

HIgh School

PS.8

PS.8.a

PH.2

PH.2.a

Minnesota Academic Standards in Science

2.1.1 9C.4.2.2.1

Arizona Science Standards

High School

HS.P3

HS.P3U1.6

Alabama Course of Study Science

Motion and Stability: Forces and Interactions

9-12.P.1.1

9-12.P.1.1.a

Florida Department of Education

SC.912.P.12

SC.912.P.12.2

Texas Essential Knowledge and Skills

PHYS.5

PHYS.5.A

PHYS.5.C

Chemistry and Physics

IPC.5

IPC.5.A

Georgia Standards of Excellence

SPS8.

Describing Motion

SP1.

One-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

The average velocity during a time interval cannot tell us how fast or in what direction a particle is moving at any given time during the interval. To ...

Instantaneous Velocity - II

Instantaneous velocity is the quantity that measures how fast an object is moving along its path. In other words, the instantaneous velocity of an object ...

The importance of understanding acceleration spans our day-to-day experiences, as well as the vast reaches of outer space and the tiny world of subatomic ...

Instantaneous Acceleration

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Position and Displacement Vectors

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average-and-instantaneous-velocity-vectors

Average and Instantaneous Velocity Vectors

To calculate other physical quantities in kinematics, the time variable must be introduced. The time variable not only allows us to state where an object ...

Acceleration Vectors

In everyday conversation, accelerating means speeding up. Acceleration is a vector in the same direction as the change in velocity, &#916;v, therefore the ...

Direction of Acceleration Vectors

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Linear Momentum

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Force and Momentum

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Electrical Current

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Drift Velocity

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Current Density

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Resistivity

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Resistance

When a current moves through any conductor, the conductor causes some level of difficulty for the current to flow. The measure of that difficulty is known ...

Ohm's Law

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Non-ohmic Devices

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Construct an explanation to compare simple series and parallel circuits in terms of Ohm's Law.

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

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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

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Torque On A Current Loop In A Magnetic Field

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The Hall Effect

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Consider a mobile phone battery ...

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magnetic-force-between-two-parallel-currents

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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.

Average Acceleration and Velocity Change

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