Name: how mass differs from weight
Uploaded: 2023-09-22T11:49:39.000Z
Duration: 1 min 19 s
Channel: JoVE

La masse d’un objet est une mesure de la quantité de matière qu’il contient et dépend du nombre d’atomes qu’il contient.
Son poids est la force gravitationnelle qui agit sur lui à partir d’un objet plus grand, comme la Terre ou la Lune, selon ce qui est le plus proche de lui.
Comme la quantité de matière ne change pas en réponse à la force appliquée, la masse de l'objet reste constante.
Cependant, son poids dépend de son emplacement. Un objet sur Terre pèse différemment de celui sur Mars ou sur la Lune, mais sa masse reste la même. Le changement de poids est dû à la différence d’accélération due à la gravité qui agit sur elle.
La masse ne peut jamais être nulle, mais le poids devient nul lorsque la force gravitationnelle n’agit pas sur elle. En utilisant cette observation et la deuxième loi de Newton, un objet de masse m pèse m fois vecteur g.
C’est-à-dire que plus la masse d’un objet est grande, plus son poids est important. La masse est une quantité scalaire, mais le poids est un vecteur dirigé vers le centre de la Terre.

masse et poids

La masse et le poids sont souvent utilisés indifféremment dans le langage courant. Par exemple, les dossiers médicaux montrent souvent notre poids en kilogrammes, mais jamais dans les unités correctes de newtons. En physique, cependant, il y a une distinction importante. Le poids est la force exercée par la Terre sur un objet. Il dépend de la distance par rapport au centre de la Terre. Le poids varie considérablement si nous quittons la surface de la Terre, contrairement à la masse qui ne varie pas en fonction de l'emplacement. Sur la Lune, par exemple, l'accélération due à la gravité est seulement de 1,67 m/s2 par rapport à 9,8 m/s2 sur Terre. Par conséquent, une masse de 1,0 kg a un poids de 9,8 N sur Terre, mais seulement environ 1,7 N sur la Lune. Cependant, la masse d'un objet est la même sur la surface de la Terre, en orbite ou sur la surface de la Lune.

Lorsqu'un objet est lâché, il accélère vers le centre de la Terre. La deuxième loi de Newton déclare qu'une force nette sur un objet est responsable de son accélération. Si la résistance de l'air est négligeable, la force nette agissant sur un objet en chute libre est égale à la force gravitationnelle, communément appelée son poids, ou la force due à la gravité agissant sur un objet de masse m.

Notez que, bien qu'ils soient étroitement liés, le poids et la masse sont des quantités physiques différentes. La masse est une propriété intrinsèque d'un objet ; c'est une quantité de matière. Il est tentant d'équivaloir la masse au poids parce que la plupart de nos exemples se déroulent sur Terre, où le poids d'un objet varie minimement selon l'emplacement de l'objet sur Terre. De plus, il est difficile de compter et d'identifier tous les atomes et molécules dans un objet, donc la masse est rarement déterminée de cette manière.

Ce texte est adapté de<a href="https://openstax.org/books/university-physics-volume-1/pages/5-4-mass-and-weight"> Openstax, University Physics Volume 1, Section 5.4: Mass and Weight.</a>

Masse et poids

La masse et le poids sont souvent utilisés de manière interchangeable dans la conversation quotidienne. Par exemple, les dossiers médicaux indiquent souvent notre poids en kilogrammes, mais jamais...

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Les bases de la physique

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Mass and Weight

how mass differs from weight

Mass and weight are related, but they are not the same. Mass is the amount of matter in an object. Weight is the force of gravity acting on that object.

This difference matters because mass stays the same even when gravity changes. Weight can change if the gravitational pull changes. A person or object therefore has the same mass, but not always the same weight.

The terms are often used in everyday speech as if they mean the same thing. In physics, they describe two different ideas. Understanding both helps students read science problems and compare objects more accurately.

How Mass Differs from Weight

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Learn how mass and weight are different in physics. This K12 science video explains mass as matter and weight as the force of gravity on an object.

How Mass Differs from Weight | JoVE K12

JoVE Core Mechanical Engineering offers concise, easy-to-understand animated videos covering key topics such as equilibrium, forces, truss analysis, and structural mechanics. Explore their real-world applications, and witness these concepts in action through scientist-led experiments.

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How Mass Differs from Weight

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