What is the difference between inertia and Newton's First Law?

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Discussion Overview

The discussion revolves around the concepts of inertia and Newton's First Law of Motion, exploring their definitions, relationships, and distinctions. Participants are trying to understand whether inertia is equivalent to Newton's First Law, as well as the historical context of these ideas.

Discussion Character

  • Conceptual clarification
  • Debate/contested
  • Meta-discussion

Main Points Raised

  • Some participants assert that inertia is the property of an object to maintain a constant velocity unless acted upon by an external force, suggesting this aligns with Newton's First Law.
  • Others argue that Newton's First Law specifically defines force as the agent that disturbs an object's state of uniform motion, indicating a distinction between the two concepts.
  • A participant mentions that inertia describes an object's resistance to motion, while another counters that any force, regardless of size, can initiate motion, challenging the notion of needing a "strong enough" force.
  • There is confusion about whether inertia and Newton's First Law are the same, with some participants feeling that inertia does not account for velocity, acceleration, and position, unlike Newton's law.
  • One participant notes that inertia is an abstract concept that cannot be measured directly, while Newton's First Law is referred to as the "law of inertia," suggesting a relationship between the two.
  • Another participant introduces the idea that inertial mass can be quantified, which relates to the concept of inertia in a measurable way.
  • Historical context is brought up, with references to Galileo's contributions to the concept of inertia and how Newton expanded on these ideas.
  • A participant seeks clarification on the term "coasting," which is described as moving with a constant velocity without resistance.

Areas of Agreement / Disagreement

Participants express differing views on whether inertia and Newton's First Law are equivalent, with no consensus reached. The discussion includes both agreement on certain definitions and significant disagreement regarding the implications and interpretations of these concepts.

Contextual Notes

Some participants express uncertainty about the terminology and concepts due to language barriers, which may affect their understanding of the discussion. Additionally, there are unresolved questions about the historical development of these ideas and the precise definitions of inertia and force.

Saska
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I'm taking my first Physics course (it's a foreign language), and in English class we were given a piece of paper on Skating taken from an English Physics textbook. We are having problems with some expressions, such as Inertia. What the heck is inertia? Is it a law? Or an expression? (I checked in my dictionary, found nothing useful)

Taken from textbook:
Inertia
A body in motion tends to remain in motion, a body at rest tends to remain at rest.

Then on the following page, they bring up Newton's First law.
Newton's First Law
An object that is not subject to any outside forces moves at a constant velocity, covering equal distances in equal times along a straight line path.

Some of my mates said that Inertia and Newton's First law is the same thing. Are they right? How the can it be the same thing? Newton's Law is a law, while inertia is ... well, something else.
 
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Inertia is the property of any object to maintain a constant velocity, i.e., constant speed in the same direction unless acted upon by an external force. So, you see. written like this it becomes the same as Newton's first law. This velocity can be zero, and then it is called the inertia of rest.

But, in addition, Newton's first law defines force as that agent which tends to disturb the body from its state of uniform motion.

Newton's second law tells you how to measure the force.
 
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Saska said:
I'm taking my first Physics course (it's a foreign language), and in English class we were given a piece of paper on Skating taken from an English Physics textbook. We are having problems with some expressions, such as Inertia. What the heck is inertia? Is it a law? Or an expression? (I checked in my dictionary, found nothing useful)

Taken from textbook:


Then on the following page, they bring up Newton's First law.


Some of my mates said that Inertia and Newton's First law is the same thing. Are they right? How the can it be the same thing? Newton's Law is a law, while inertia is ... well, something else.

Inertia is the word describing the property for an object to resist against a motion. Thus you have to push the object with a strong enough force if you want to move it. As long as you don't, as long as the object resists (due to its inertia; but sometimes also because of the frictions), it does not move. It stays at rest.
 
Blackforest said:
Thus you have to push the object with a strong enough force if you want to move it.

If you push an object at rest with any force, however small, it will move, with however samll acceleration. There is nothing like pushing it with a strong enough force. The resultant of all forces, including friction, has to be non-zero.
 
A body in motion tends to remain in motion, a body at rest tends to remain at rest.
Is that only saying that a Force is required to change a body's position?
 
OK, I'm not sure i got everything (Remember, english is not my mummy-tongue) I get Newtons law, that's all right. I just don't get if Inertia and his law is the same thing. If it really is the same thing, why have two laws that explain precisely the same thing.(jeez hwo many times did I use "thing"?)

I don't get it.

EDIT: To me more precise. I DO understand this sentence: A body in motion tends to remain in motion, a body at rest tends to remain at rest. and I do indeed understand this sentence: An object that is not subject to any outside forces moves at a constant velocity, covering equal distances in equal times along a straight line path. . What I need to know if they are the same thing.

To me, IMO, it doesn't seem to be, as Inertia does not take velocity, acceleration and position etc in consideration, whilst Newtons law does. (?)

Clarification?


Also what confuses me is that who the heck came up with the concept? Galileo or Newton? Didnt galileo claim (quoting from textbook)
someone is stationary, the person in question will remain stationary, the same principle applies to if someone is moving (he/she will continue moving) in a steady pace and in the very same direction.

Kind of sounds like Newtons law.


PPS: What is COASTING? It says "coasting is one of the most basic concepts in physics" ... but nothing else
 
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Inertia is the property of the body to maintain its state of rest or of uniform motion in a st line. (As I had said, this means const velo.)

Nweton's first law says that this state of rest or motion can be changed by something called a force.

What more is confusing?
 
To "coast" is to move with a constant velocity without being slowed by a resisting force. An ice skater "coasts" along the ice. It's not a term that is used in a very technical way. Sometimes we say someone is "coasting along" if they are moving through something without effort.

Inertia is an abstract concept. It does not refer to any measurable property, and you can't place a number on it. It's just a "tendency." Newton's First Law is called the "law of inertia."
 
Zorodius said:
...Inertia is an abstract concept. It does not refer to any measurable property, and you can't place a number on it. It's just a "tendency." Newton's First Law is called the "law of inertia."

This is partially not exact. Since force = inertial mass x acceleration, the inertial mass is the number that you place on the inertia of the concerned body. You state that for any given (and non zero force) the greater is the inertia, the smaller is the acceleration resulting from the applied force. Perhaps is it the tendency you are speaking about.
 
  • #10
Galileo gave the inertia law, Newton finished the story...
 

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