Name: why motion seems different in accelerating frames
Uploaded: 2023-04-30T10:54:29.000Z
Duration: 1 min 27 s
Channel: JoVE

K12 Standards

Pennsylvania State Academic Standards

9-12

Physical Science

Forces and Interactions

3.2.9-12.J

Non-inertial Frames of Reference

Lembre-se de que os referenciais em que as leis de Newton são verdadeiras são conhecidos como referenciais inerciais. No entanto, existem sistemas de referência que desafiam as leis de Newton, chamados de sistemas de referência não inerciais.
Os referenciais não inerciais estão acelerando ou desacelerando em relação aos referenciais inerciais.
Por exemplo, quando um avião decola, os passageiros sentem uma força para trás oposta à aceleração do avião. Isso viola a segunda lei de Newton, segundo a qual os objetos são acelerados na direção da força externa líquida.
Em referenciais não inerciais, forças inerciais ou fictícias que não têm origem física são necessárias para explicar o movimento dos objetos. Portanto, na mecânica, é mais conveniente usar um referencial inercial.
Idealmente, um sistema de referência fixado à Terra não é inercial devido à sua revolução e rotação. No entanto, as forças devidas à rotação da Terra são insignificantes em pequenos movimentos mecânicos, mas afetam movimentos de grande escala, como padrões de vento.
A força fictícia neste referencial desvia o vento no sentido horário no hemisfério norte e no sentido anti-horário no hemisfério sul.

Não há conflitos de interesse declarados.

referenciais não inerciais

Um referencial que acelera ou desacelera em relação a um referencial inercial é um referencial não inercial. Para ajudar a entender isso, considere o que há de comum em decolar em um avião, virar uma esquina em um carro, andar em um carrossel e o movimento circular de um ciclone tropical. A resposta é que todos esses sistemas estão acelerando, desacelerando ou girando em relação à Terra, portanto, todos são referenciais não inerciais. Todos esses sistemas apresentam forças inerciais, que apenas parecem surgir do movimento, porque o referencial do observador está acelerando, ou girando. Podemos conciliar esses pontos de vista examinando os referenciais utilizados. Um físico escolherá o referencial mais conveniente para a situação em análise. Os físicos não têm problema em incluir forças inerciais e a segunda lei de Newton, como de costume, se isso for mais conveniente. Da mesma forma, referenciais não inerciais (acelerados) são usados quando são úteis. Diferentes referenciais devem ser considerados, por exemplo, ao discutir o movimento de um astronauta em uma espaçonave viajando em velocidades próximas à velocidade da luz, pois isso se aplica à teoria especial da relatividade.

A Terra pode ser usada como um referencial inercial com pouca ou nenhuma preocupação com quaisquer efeitos causados ​​por sua rotação. No entanto, tais efeitos existem, por exemplo, na rotação de sistemas climáticos. Vista de cima, do Polo Norte, a Terra gira no sentido anti-horário, e qualquer movimento no hemisfério norte da Terra experimenta uma força de Coriolis para a direita. O oposto ocorre no hemisfério sul, onde a força é para a esquerda. Como a velocidade angular da Terra é pequena, a força de Coriolis geralmente é negligenciável, mas tem efeitos substanciais para movimentos em grande escala, como padrões de vento. A força de Coriolis faz com que os furacões no hemisfério norte girem no sentido anti-horário, enquanto os ciclones tropicais no hemisfério sul giram no sentido horário.

A rotação de ciclones tropicais e o caminho de uma bola em um carrossel podem ser igualmente explicados pela inércia e pela rotação do sistema envolvido. Quando referenciais não inerciais são usados, forças inerciais, como a força de Coriolis, devem ser inventadas para explicar o caminho curvo. Não há uma fonte física identificável para essas forças inerciais. Quando referenciais inerciais são utilizados, a inércia explica o caminho percorrido, e há uma fonte identificável para cada força. Podemos usar qualquer uma dessas visões para descrever a natureza, mas uma visão a partir de um referencial inercial é mais simples, pois todas as forças têm origem e explicações.

Este texto foi adaptado de <a href="https://openstax.org/books/university-physics-volume-1/pages/5-6-common-forces">Openstax, University Physics Volume 1, Section 5.6: Common Forces</a> and<a href="https://openstax.org/books/university-physics-volume-1/pages/6-3-centripetal-force"> Section 6.3: Centripetal Force.</a>

Referenciais não inerciais

Um referencial acelerando ou desacelerando em relação a um referencial inercial é um referencial não inercial. Para ajudar a entender isso, considere o que decolar em ...

Education

JoVE Core

Physics

Física

Unit 1

Unidade 1

Newton's Laws of Motion

Leis do Movimento de Newton

KEY TERMS AND CONCEPTS

TERMOS-CHAVE E CONCEITOS

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 a physical source in the usual sense. Instead, it is tied to the observer’s frame of reference.

Physicists choose the reference frame that is most useful for the problem being studied. They can use inertial frames and apply Newton’s second law in the usual way. They can also use non-inertial frames when that makes the description easier.

Different frames of reference matter in special cases, such as an astronaut in a spacecraft moving near the speed of light. This is important in the special theory of relativity. In many problems, the Earth is used as an inertial frame because its rotation causes little trouble.

Even so, Earth’s rotation does affect some motions. Viewed from above the North Pole, Earth rotates counterclockwise. Motion in the Northern Hemisphere then experiences a Coriolis force to the right, while the Southern Hemisphere experiences a force to the left.

Because Earth’s angular velocity is small, the Coriolis force is usually negligible. It still has major effects on large-scale motion, such as wind patterns. It helps explain why hurricanes in the Northern Hemisphere rotate counterclockwise and why tropical cyclones in the Southern Hemisphere rotate clockwise.

The path of a ball on a merry-go-round and the motion of a tropical cyclone can also be explained by inertia and by the rotation of the system underneath. When a non-inertial frame is used, inertial forces such as the Coriolis force must be added to explain the curved path. When an inertial frame is used, inertia explains the motion, and every force has a clear source. Both views can describe nature, but the inertial frame is usually simpler.

Why Motion Seems Different in Accelerating Frames

why-motion-seems-different-in-accelerating-frames

force

Understanding Force in Motion

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Newton's First Law and Inertia

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newton's first law: application

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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...

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newton's third law: introduction

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free body diagrams: examples

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non-inertial frames of reference

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centrifugal force

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key terms and concepts

Explore how accelerating, decelerating, and rotating frames change the way motion looks, from cars and merry-go-rounds to Coriolis force and hurricanes.

Why Motion Seems Different in Accelerating Frames | JoVE K12

physics

JoVE Core - Fisica apresenta a teoria e a aplicação de tópicos fundamentais da física, incluindo cinemática, dinâmica, mecânica dos fluidos, estática, ondas e acústica, com vídeos animados concisos e de fácil compreensão. Além disso, os vídeos de cientistas em ação demonstram a aplicação de conceitos relacionados em experimentos de pesquisa clássica e original realizados nos laboratórios de todo o mundo hoje em dia.

Louisiana Student Standards for Science

High School

motion-and-stability-forces-and-interactions

Motion And Stability: Forces And Interactions

HS-PS2-2

HS-PS2-3

ohios-learning-standards-and-model-curriculum

Ohio’s Learning Standards and Model Curriculum

Forces And Motion

Motion

Tennessee Academic Standards

Motion and Stability: Forces and Interactions

PHYS.PS2.14

Virginia  Standards of Learning

HIgh School

PS.8

PS.8.b

PH.3

PH.3.a

Next Generation Science Standards

Florida Department of Education

SC.912.P.12

SC.912.P.12.3

SC.912.P.12.8

SC.912.P.12.9

Texas Essential Knowledge and Skills

PHYS.5

PHYS.5.C

new-york-state-science-learning-standards

New York State Science Learning Standards

HS. Forces and Interactions

HS-PS2-1.

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Second Law: Motion under Same Force

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3.2.9-12.I

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3.2.9-12.K

Gravitation

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Coulomb's Law

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Electromagnetic Fields

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3.2.9-12.L

Energy Transfer in Chemical Reactions

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3.2.9-12.M

Why Motion Seems Different in Accelerating Frames

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