Name: newton's first law and friction
Uploaded: 2023-04-30T10:53:13.000Z
Duration: 1 min 12 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

Physics

motion-and-stability-forces-and-interactions

Motion and Stability- Forces and Interactions

PS.Phy.2.2

Newton's First Law: Application

La première loi de Newton stipule qu'une force externe est nécessaire pour tout changement dans l'état de mouvement de l'objet.
Pour mieux comprendre cela, considérons une balle au repos. Les forces qui agissent sur elle sont la force gravitationnelle et la force normale qui sont égales en intensité et opposées en direction. Par conséquent, la force nette est équilibrée.
Si, toutefois, la balle est poussée doucement d’un côté, les forces sont déséquilibrées. Il y a une force nette agissant sur l’objet et la balle commence à rouler dans le sens de la force.
Une fois en mouvement, aucune force nette n’agit sur le ballon, mais le ballon continue de rouler. Il aurait continué à rouler éternellement s’il n’y avait pas eu la résistance de l’air et les forces de frottement. Ceux-ci agissent à l’opposé de la direction du mouvement et immobilisent la balle.
La résistance de l'objet au changement de son état de repos ou de mouvement s'appelle l'inertie. Ainsi, la première loi est également connue sous le nom de loi d’inertie.
L’inertie offerte par tout objet est directement proportionnelle à sa masse.

Aucun conflit d’intérêts n’a été déclaré.

la première loi de newton : application

L'expérience suggère qu'un objet au repos reste au repos s'il est laissé seul, et qu'un objet en mouvement tend à ralentir et s'arrêter à moins qu'un effort soit fait pour le maintenir en mouvement. Cependant, la première loi de Newton donne une explication plus profonde de cette observation. L'étude des lois de Newton revient à reconnaître des motifs dans la nature à partir desquels d'autres motifs peuvent être découverts. Le génie de Galilée, qui a développé pour la première fois l'idée de la première loi du mouvement, et celui de Newton, qui l'a clarifiée, consistait à poser la question fondamentale : « Quelle est la cause ? » Penser en termes de cause et d'effet est fondamentalement différent de l'approche typique des anciens Grecs, lorsqu’il aurait été répondues à la manière aristotélicienne à des questions telles que « Pourquoi un tigre a-t-il des rayures ? », avec la réponse « C'est la nature de la bête ». La capacité de penser en termes de cause et d'effet est la capacité de relier un comportement observé et le monde qui l'entoure.

Plutôt que de contredire notre expérience, la première loi de Newton dit qu'il doit y avoir une cause pour tout changement de vélocité (un changement de magnitude ou de direction) pour se produire. Cette cause est une force externe nette. Un objet glissant sur une table ou un sol ralentit en raison de la force nette de frottement agissant sur l'objet. Si le frottement disparaît, l'objet ralentira-t-il toujours ? L'idée de cause et d'effet est cruciale pour décrire avec précision ce qui se passe dans différentes situations. Par exemple, considérons ce qui se passe avec un objet glissant le long d'une surface horizontale rugueuse. L'objet s'arrête rapidement. Si nous rendons la surface plus lisse en la saupoudrant de poudre de talc, l'objet glisse plus loin. Si nous rendons la surface encore plus lisse en y appliquant de l'huile, l'objet glisse encore plus loin. En extrapolant à une surface sans friction et en ignorant la résistance de l'air, nous pouvons imaginer que l'objet glisse en ligne droite indéfiniment. Le frottement est donc la cause du ralentissement (conforme à la première loi de Newton). L'objet ne ralentirait pas si le frottement était éliminé.

Indépendamment de l'échelle d'un objet, qu'il s'agisse d'une molécule ou d'une particule subatomique, deux propriétés restent valables et intéressantes en physique : la gravitation et l'inertie. La gravitation est l'attraction d'une masse vers une autre, tandis que l'inertie est la capacité d'un objet à résister aux changements de son mouvement, en d'autres termes, à résister à l'accélération. La première loi de Newton est souvent appelée loi de l'inertie.

Ce texte est adapté de <a href="https://openstax.org/books/university-physics-volume-1/pages/5-2-newtons-first-law">Openstax, University Physics Volume 1, Section 5.2: Newton’s First Law.</a>

La première loi de Newton : application

L’expérience suggère qu’un objet au repos reste au repos s’il est laissé seul, et qu’un objet en mouvement a tendance à ralentir et à s’arrêter à moins qu’un effort ne soit ...

Education

Enseignement

JoVE Core

Physique

Unit 1

Unité 1

Newton's Laws of Motion

Les lois du mouvement de Newton

KEY TERMS AND CONCEPTS

TERMES ET CONCEPTS CLÉS

newton's first law and friction

Newton's first law explains why friction changes an object's motion. It says that an object at rest stays at rest, and an object in motion keeps moving unless a net external force acts on it. A net external force is the overall force from outside the object that causes a change in velocity, meaning a change in speed or direction.

This idea gives a cause-and-effect reason for motion, rather than just describing what we see. Galileo first developed the idea behind the first law of motion, and Newton clarified it. Their work was based on asking what causes a change, instead of stopping at an observation.

That approach was different from the older Aristotelian style of explanation. In that view, a question like why a tiger has stripes might be answered by saying it is simply the nature of the animal. Newton's first law instead links the observed motion of an object to the forces around it.

A common example is an object sliding across a table or floor. It slows down because friction acts as the net force on it. If the surface becomes smoother, such as with talcum powder or oil, the object slides farther before stopping.

If friction were removed and air resistance were ignored, the same object would keep moving in a straight line indefinitely. The law does not contradict everyday experience. It explains that friction is the cause of the slowing.

In physics, inertia is the ability of an object to resist changes in motion, or resist acceleration. This is why Newton's first law is often called the law of inertia. The same ideas apply at many scales, from molecules to subatomic particles, and they help describe both gravitation and inertia as important properties of matter.

Newton's First Law and Friction

force

Understanding Force in Motion

Force is a push or pull that acts on an object. It has both magnitude and direction, so force is a vector quantity. In everyday life, force appears when we open a door, walk down a street, lift a fork, or touch a baby's face. Forces also shape matter at the smallest scales. The atoms in our bodies are held together by electrical forces. The nucleus of an atom is held together by nuclear force, which is the strongest force known to us. The study of motion is called kinematics. Kinematics...

types of forces

Contact and Field Forces in Physics

Forces in physics are often grouped as contact forces and field forces. Contact forces happen when objects touch directly. Field forces act without direct physical contact. They come from a field, which is a region of space that can be detected by the force it exerts on a body. Scientists describe four fundamental force fields in nature: gravitational, electromagnetic, strong nuclear, and weak nuclear. The gravitational field gives a body its weight. The electromagnetic field includes static...

newton's first law: introduction

Newton's First Law and Inertia

Newton's first law of motion explains inertia and how forces change motion. Motion can be striking to observe, from a dolphin jumping from water to a bird in flight or a satellite moving in orbit. The study of motion is kinematics, which describes velocity and acceleration. Dynamics goes further by examining the forces that affect moving objects and systems. Newton's laws of motion are the foundation of dynamics. They are simple in form, but they describe a wide range of natural behavior.

newton's first law: application

Newton's first law explains why friction changes an object's motion. It says that an object at rest stays at rest, and an object in motion keeps moving unless a net external force acts on it. A net external force is the overall force from outside the object that causes a change in velocity, meaning a change in speed or direction. This idea gives a cause-and-effect reason for motion, rather than just describing what we see. Galileo first developed the idea behind the first law of motion, and...

internal and external forces

External Forces and Motion Changes

External forces and motion changes are linked in Newton’s first law. A net external force causes a change in motion. External forces act on an object or system from outside that object or system. Internal forces come from inside the system of interest. They act on one part of an object and are exerted by another part of the same object. These forces do not cause acceleration when the whole system is studied. When analyzing motion, the internal forces are ignored. Instead, only the external...

newton's second law

Force, Mass, and Acceleration

Newton's second law connects net force, mass, and acceleration. It explains how an object's motion changes when external forces act on it. The law gives a clear cause-and-effect link that can be used to make calculations. All external forces on a system are added together to find the net force, or F net. A larger net external force produces a larger acceleration. The acceleration points in the same direction as the net force. Mass also affects the result. A larger mass means more inertia, so...

mass and weight

Weight Changes, Mass Stays Constant

Mass and weight are related, but they are not the same. In physics, weight is the pull of the Earth on an object. It depends on how far the object is from the center of the Earth. Mass is the amount of matter in an object, and it does not change with location. Everyday language can make this difference confusing. Medical records often list body weight in kilograms, even though the correct force unit is the newton. That can make mass and weight seem interchangeable. In physics, however, they...

weightlessness

Weightlessness in Free Fall

Weightlessness happens when contact forces disappear, even though gravity is still present. In physics, an object in free fall has only gravity acting on it. If the net external force on the object is its weight, the object is accelerating toward the center of the Earth. Galileo showed that, without air resistance, all objects fall with the same acceleration g. On Earth, falling objects are never truly in free fall because air always pushes upward with some resistance force. That is why real...

apparent weight

Scale Readings in Motion and Water

Scale readings can change when an object is moving or submerged in water. The force we call true weight is the gravitational force acting on an object. When motion or fluid forces are present, the reading can differ from that true weight. In water, this changed reading is called apparent weight, and it equals true weight minus the buoyant force. A bathroom scale in an elevator shows how this works. At rest, the scale reads the force the person pushes downward on it. The only forces on the...

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newton's third law: introduction

Newton's Third Law in Force Pairs

Newton's third law explains how force pairs work in motion and interactions. When one body exerts a force on a second body, the first body experiences a force that is equal in magnitude and opposite in direction. A simple example is a person pushing on a wall. The wall pushes back on the person with an equal and opposite force. This is why Newton's third law is often described as action and reaction, where the action is the force exerted and the reaction is the force experienced afterward. <br...

newton's third law: examples

Newton's Third Law in Motion

Newton's third law explains how forces come in pairs during motion. It says that every action has an equal and opposite reaction. In these examples, the two forces act on different systems, so they do not cancel each other out. A swimmer pushing off the side of a pool shows this clearly. The swimmer pushes against the wall with their feet and then accelerates in the opposite direction. The wall pushes back with an equal and opposite force. If the swimmer is the system of interest, the wall's...

drawing free-body diagrams: rules

Free-Body Diagrams for Newton’s Laws

Free-body diagrams help students map the forces acting on an object in physics. They are used often when studying and applying Newton’s laws of motion. A clear diagram makes it easier to analyze a system before solving for motion. Start by drawing the object under consideration. If the object is treated like a particle, show it as a point and place that point at the origin of an x-y coordinate system. Then add every force that acts on the object as a vector. Do not include the net force on the...

free body diagrams: examples

Free Body Diagram Force Examples

Free body diagrams show the external forces acting on an object or system. The object is drawn as a single isolated point, or free body, so the forces are easier to analyze. Only forces that come from outside the object or system are included. These forces are shown as vectors pointing away from the free body. A person sitting on a chair is a simple example. The free-body diagram has two forces. The chair exerts an upward normal force, and gravity pulls downward with the weight. A rocket sled...

inertial frames of reference

Newton's First Law and Reference Frames

Newton's first law helps identify inertial reference frames. An inertial reference frame is one in which Newton's first law holds true. In that frame, an object with no net force moves at constant velocity. A key idea is that any frame moving at constant velocity relative to an inertial frame is also inertial. For that reason, inertial frames can be found by comparing motion from one frame to another. The laws of physics do not give one inertial frame special status over another. In nature, a...

non-inertial frames of reference

Why Motion Seems Different in Accelerating Frames

A non-inertial frame of reference is a frame that accelerates, decelerates, or rotates relative to an inertial frame. In these frames, motion can look unusual because the observer is moving with the system. That is why an airplane taking off, a car turning a corner, a merry-go-round, and a tropical cyclone can all be examples of non-inertial motion. These situations can show inertial forces, which seem to appear because the frame itself is accelerating or rotating. The force does not come from...

centrifugal force

Rotating Frames and Pseudo Forces

Pseudo forces, also called fictitious forces, appear in a rotating frame of reference when compared with an inertial frame. They are not real forces. Instead, they are mathematical tools that help make Newton&amp;#39;s laws of motion easier to use in a non-inertial frame. Common examples include centrifugal, Coriolis, and Euler forces. These forces matter in mechanics, astrophysics, and fluid dynamics. In these areas, motion is often described from a frame that is not inertial. That is why...

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key terms and concepts

Learn how Newton's first law connects motion, friction, and inertia. See why objects slow down and how reduced friction changes motion in everyday examples.

Newton's First Law and Friction | 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.

ohios-learning-standards-and-model-curriculum

Ohio’s Learning Standards and Model Curriculum

Physical Science

Forces And Motion

Dynamics (how forces affect motion)

Forces, Momentum And Motion

newton-s-laws-applied-to-complex-problems

Newton's laws applied to complex problems

Tennessee Academic Standards

High School

Motion and Stability: Forces and Interactions

PHYS.PS2.4

Virginia  Standards of Learning

HIgh School

PS.8

PS.8.b

PH.3

PH.3.a

Alabama Course of Study Science

9-12.P.1.2

Florida Department of Education

SC.912.P.12

SC.912.P.12.3

Texas Essential Knowledge and Skills

PHYS.5

PHYS.5.E

new-york-state-science-learning-standards

New York State Science Learning Standards

HS. Forces and Interactions

HS-PS2-1.

Georgia Standards of Excellence

SPS8.

SP2.

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PS.Phy.1.2

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PS.Phy.2.1

Newton's First Law: Introduction

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Carry out investigations to explain the interactions of forces on an object according to Newton's Laws of Motion.

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Newton's First Law and Friction

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