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Old Sep 20th 2018, 09:26 AM   #1
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What inspired newton to formulate his laws of motion?

Well Pmb used to say that you should try to investigate how laws of physics were formed. So as per my thinking newton formulated his laws based on law of conservation of energy. Is this correct?

Let me elaborate. Newtons first law states that an object at rest remains at rest and object in motion remains in motion at constant speed in a straight line unless acted upon by external force. Now observe the continuous motion in same speed could mean conservation of velocity.

Now third law. It says every action has a reaction. So here say a billiard ball hits another then the momentum is transferred and remains in conservation.

What are your views. Especially asked to studiot.
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Old Sep 20th 2018, 02:50 PM   #2
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Originally Posted by avito009 View Post
Well Pmb used to say that you should try to investigate how laws of physics were formed. So as per my thinking newton formulated his laws based on law of conservation of energy. Is this correct?

Let me elaborate. Newtons first law states that an object at rest remains at rest and object in motion remains in motion at constant speed in a straight line unless acted upon by external force. Now observe the continuous motion in same speed could mean conservation of velocity.

Now third law. It says every action has a reaction. So here say a billiard ball hits another then the momentum is transferred and remains in conservation.

What are your views. Especially asked to studiot.
The First Law is commonly referred to as the "Law of Inertia." I look at it slightly differently: it's the definition of what the (net) force on an object does.

I don't know the origin of the Second Law but you might find this to be of interest. Newton wrote the law as $\displaystyle \sum F = \dfrac{dp}{dt}$, not as $\displaystyle \sum F = ma$. The value of the original version is that mass does not have to be constant, so it's more general.

The Third Law comes in two varieties: The weak version is what you stated: equal and opposite reactions. The strong form is that these reactions are along the same line, not just equal magnitude forces.

Hope it helps!

-Dan
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Old Sep 20th 2018, 06:15 PM   #3
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Is mass the least complicated "Conservation Principle?

Below I update my ideas. I am not trying to "bump" the topic.

What Newton (and others) meant is less important than what's needed today for ourselves, our students. For applications today, might some reformulation be of value.

********************
Newton's Laws and the "conservation" ideas germinated in relativlely the same time period. The
seminal "conservation" idea addressed energy of a Body. So there was supposed "Conservation of Energy."
Thence, logically might momentum of a Body be conserved? And in afterthought "Conservation of Mass" makes sense for the Body - implicitly.

The matter of interest was modelled as a Body (mass at a point and having no extent). "Conservation of mass" applied to "some specific mass, selected at a time <b>t*</b> thereafter modeled as a point with no extent nor "boundary." The Body exists in space we call "extrinsic space." Other (more logical) models of matter exist in "extrinsic space" in terms of their centers of mass, but als in "intrinsic space" meaning the mass might have shape, deform and so.

The idea "mass of a Body is conserved" is represented by the mathematical equation:
(a) m(Body) = const. which is a non-homogeneous equation. A better statement is:
(b) d[m(Body)]/dt =0. A question here. Why is (b)superior to (a)?
=====================

Comments Here:
1) This is "about in Newton's time." "Body" is the model.
2) As we see it, the idea, "Conservation of mass" has mathematical representation as an equation with
a property of the Body as dependent variable.
3) The equation "conservation of mass" is a "property equation" for the Body.

I am not trying to "bump" my topic. Rather to develop it. Thank you
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Last edited by THERMO Spoken Here; Sep 22nd 2018 at 02:54 PM. Reason: correction needed
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Old Sep 27th 2018, 04:35 AM   #4
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