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 prima legge di Newton afferma che è necessaria una forza esterna per qualsiasi cambiamento nello stato di movimento dell'oggetto.
Per capirlo meglio, considera una palla a riposo. Le forze che agiscono su di esso sono la forza gravitazionale e la forza normale che sono uguali in grandezza e opposte in direzione. Quindi, la forza netta è bilanciata.
Se, tuttavia, la palla viene spinta dolcemente da un lato, le forze sono sbilanciate. C'è una forza netta che agisce sull'oggetto e la palla inizia a rotolare nella direzione della forza.
Una volta in movimento, nessuna forza netta agisce sulla palla, ma la palla continua a rotolare. Avrebbe continuato a rotolare per sempre se non fosse stato per la resistenza dell'aria e le forze di attrito. Questi agiscono in senso opposto alla direzione del movimento e portano la palla a fermarsi.
La resistenza dell'oggetto al cambiamento nel suo stato di quiete o movimento è chiamata inerzia. Pertanto, la prima legge è anche conosciuta come legge di inerzia.
L'inerzia offerta da qualsiasi oggetto è direttamente proporzionale alla sua massa.

Nessun conflitto di interessi dichiarato.

prima legge di newton: applicazione

L'esperienza ci suggerisce che un oggetto a riposo rimane tale, se lasciato solo, e che un oggetto in movimento tende a rallentare e a fermarsi, se non viene fatto uno sforzo per mantenerlo in movimento. Tuttavia, la prima legge di Newton fornisce una spiegazione più approfondita di questa osservazione. Lo studio delle leggi di Newton equivale a riconoscere modelli in natura da cui possono esserne scoperti altri. Il genio di Galileo, che per primo ha sviluppato l'idea per la prima legge del movimento, e Newton, che l'ha spiegata, si posero una domanda fondamentale: Qual è la causa? Pensare in termini di causa ed effetto è essenzialmente diverso dal tipico approccio dell'antica Grecia, quando una domanda come "Perché la tigre ha le strisce?" avrebbe avuto una risposta Aristotelica, come "Quella è la natura della bestia". L'abilità di pensare in termini di causa ed effetto è l'abilità di collegare un comportamento osservato con il mondo circostante.

Piuttosto che contraddire la nostra esperienza, la prima legge di Newton dice che dev'esserci una causa per ogni cambiamento che avviene nella velocità (che sia di grandezza o di direzione). Questa causa è una forza esterna. Un oggetto che scivola attraverso il tavolo o il pavimento rallenta a causa della forza di frizione che agisce sull'oggetto. Se la frizione scompare, l'oggetto rallenterà ancora? L'idea di causa ed effetto è cruciale nel descrivere accuratamente cosa succede in varie situazioni. Per esempio, consideriamo cosa succede a un oggetto che scivola su una superficie ruvida. L'oggetto si ferma rapidamente. Se rendiamo la superficie più liscia applicandoci dell'olio, l'oggetto scivolerà più lontano. In una condizione in cui la superficie non ha attrito e si ignora la resistenza dell'aria, possiamo immaginare che l'oggetto scivolerà in linea retta per sempre. L'attrito è quindi la causa del rallentamento (coerente con la prima legge di Newton). Se la frizione venisse eliminata l'oggetto non rallenterebbe.

Indipendentemente dalla dimensione dell'oggetto, che si tratti di una molecola o di una particella subatomica, in fisica rimangono valide due proprietà: la gravitazione e l'inerzia. La gravitazione è l'attrazione di una massa verso l'altra, mentre l'inerzia è la capacità di un oggetto di resistere ai cambiamenti del suo movimento, in altre parole, di resistere all'accelerazione. La prima legge di Newton è chiamata legge di inerzia.

Questo testo è stato tratto e adattato da <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>

Prima legge di Newton: applicazione

L'esperienza suggerisce che un oggetto a riposo rimane a riposo se lasciato solo, e che un oggetto in movimento tende a rallentare e fermarsi a meno che non venga fatto uno sforzo ...

Education

Didattica

JoVE Core

Fisica

Unit 1

Unità 1

Newton's Laws of Motion

Le leggi del moto di Newton

KEY TERMS AND CONCEPTS

TERMINI E CONCETTI CHIAVE

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 Physics introduces the theory and application of fundamental physics topics, including kinematics, dynamics, fluid mechanics, statics, waves, and acoustics, with concise and easy-to-understand animated videos. Additionally, the scientist-in-action videos demonstrate the application of related concepts in classical and original research experiments performed in today's laboratories worldwide.

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.1.1

Position and Displacement Vectors

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Relative Velocity in One Dimension

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PS.Phy.1.2

Force

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Types of Forces

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Drawing Free-body Diagrams: Rules

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Use free body models to qualitatively and quantitatively analyze systems of forces in one dimension and two dimensions.

PS.Phy.2.1

Newton's First Law: Introduction

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Internal and External Forces

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Newton's Second Law

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Newton's Third Law: Introduction

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Newton's Third Law: Examples

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

Analyze the motion of objects using time, distance, displacement, speed, velocity, and acceleration.

Newton's First Law and Friction

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