Talk:Newton's laws of motion

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Figure skaters and 3rd law[edit]

hi, I wonder if the figure skater diagram is optimal? It doesn't indicate any forces: are they holding hands while spinning? are they (about) to push apart? Are there any forces at all involved?

Also, the key 3rd law concept is that of opposite laws: An ideal diagram would show one person pushing the other, and experiencing a force back into their body (the opposite reaction, and also the correct image for a free body diagram... ojryosryun9zeryjzu9tja9*


I removed the following as the conservation of energy article disproves it: Conservation of energy was discovered nearly two centuries after Newton's lifetime, the long delay occurring because of the difficulty in understanding the role of microscopic and invisible forms of energy such as heat and infra-red light.

Newton's 3rd law actually discovered by Leonardo da Vinci[edit]

I can't seem to edit the article... can someone add that Newton's 3rd law was actually discovered by Leonardo da Vinci? Just google 'da vinci 3rd law' for a bunch of sources

The role of the 3rd law in self-consistency with respect to scaling up from subsystem to system[edit]

The question of what Newton's laws actually apply to (fundamental bodies or extended systems) should be addressed. Definitions I and II in the Principia characterize bodies as extended objects whose mass and momentum are (what we in the current era would call) the volume integrals respective of density and density multiplied by velocity; and Definition IV described the force applied to the body as the total external force (or "impressed" force) applied to its parts.

It needs to be noted that this raises the issue of self-consistency: does a system, whose parts each satisfy Newton's laws, also satisfy those laws, and if so, what mass, momentum, position and velocity is to be ascribed to the system that the laws are to be taken with respect to.

In this context, (1) the first law can also be characterized as a "no self-force" law; (2) the underlying additivity assumption for mass, mass moment, momentum and force needs to be noted (with references to relevant parts of the Principia), (3) the role should also be noted that the third law plays for self-consistency with respect to scaling up from subsystems to systems, by ensuring that the internal forces within a system do not produce a net self-force (so that the only force that acts on the system is the sum of the "impressed" forces), (4) that the requirement of self-consistency also implies the third law and (5) the first law becomes a special case of the third law, when the latter is generalized to also include the case where the two bodies in question are one and the same. (It's not entirely clear whether the original wording of the third law already does so or not.)

Finally, there is the ambiguity inherent in Third Law's statement: is it meant to also assert that the forces acting between two subsystems act along the line separating the two. The wording in the Principia (particularly with the examples raised), tends to suggest this but leaves the issue open. It is required for self-consistency with respect to the matter of angular momentum and self-torques (which in turn has a bearing on Kepler's law of Area, which Newton used as one of the motivations for his work).

The question of ambiguity of the Third Law has been noted in the literature. References to the different interpretations should be provided, and at the very least, a distinction should be noted between a "strong" form of the Third Law (equal, opposite and directed toward or away from each other) versus the "weak" form (equal, opposite, but not necessarily directed toward or away from each other). It hinges partly on whether the extra clause "et in partes contrarias dirigi" ("directed to contrary parts") in the Third Law is meant as "directed toward or away from each other" or not. A possible reference on this may be V. F. Lenzen, Isis, Vol. 27, No. 2 (Aug., 1937), pp. 258-260; though I don't have access to it.

Action and reaction with velocity[edit]

Newton's original Latin reads:

Hisce volui tantum ostendere quam late pateat, quamq; certa sit Lex tertia motus. Nam si aestimetur Agentis actio ex ejus vi et velocitate conjunctim; et Resistentis reactio ex ejus partium singularum velocitatibus et viribus resistendi ab earum attritione, cohaesione, pondere et acceleratione oriundis; erunt actio et reactio, in omni instrumentorum usu, sibi invicem semper aequales. Et quatenus actio propagatur per instrumentum et ultimo imprimitur in corpus omne resistens, ejus ultima determinatio determinationi reactionis semper erit contraria.

from Philosophiae Naturalis Principia Mathematica, Axiomata, sive Leges Motus, P.24,_sive_Leges_Motus

Translated to English, this reads:

I was only willing to show by those examples the great extent and certainty of the third Law of motion. For if we estimate the action of the agent from its force and velocity conjunctly, and likewise the reaction of the impediment conjunctly from the velocities of its several parts, and from the forces of resistance arising from the attrition, cohesion, weight, and acceleration of those parts, the action and reaction in the use of all sorts of machines will be found always equal to one another. And so far as the action is propagated by the intervening instruments, and at last impressed upon the resisting body, the ultimate determination of the action will be always contrary to the determination of the reaction.

from The Mathematical Principles of Natural Philosophy, Axioms or Laws of Motion, P.24,_or_Laws_of_Motion

F1v1 = -F2v2



Just an idea[edit]

For any object in space– omitting gravity, IMPOV

An object of any mass (continuous) irrespective of size can be pushed or pulled without any resistance - Right?

It is the gravitating mass, due to which a falling mass shows resistance because of its weight against another force. For Example an object on earth. If this is true then shouldn’t the definition or the concept of inertia, which means resistance, needs revising.

No idea id someone agrees with the following but

An object is said to be in a state of a well-balanced condition if its centroid or center of mass (c.o.m) locates itself at its spontaneous strategic position if left on its own accord. An undisturbed mass at rest is always in well-balanced condition.

An aforementioned object is said to be in a state of an unbalanced condition if its c.o.m off its strategic position due to any means. The course of the shifting of the centroid, which is under duress due to an unbalanced condition, not only moves the object forward but also guides the direction of its motion. A disturbed mass is always at unbalanced condition - Motion. Thus

An object is said to be at rest if its c.o.m remain at its original position.

An object is said to be in a state of motion if its c.o.m off its original position.

An object may spin about its undisturbed c.o.m in the direction of applied force when only a part of the mass is disturbed.

A mass may spin and move if its c.o.m and a part of the mass are disturbed.

An object may also be found at fully or partially disturbed and undisturbed conditions

Let A and B are two spherical objects of masses M and m at rest such that A > B and therefore M > m. Ca and Cb are the center of masses of A and B respectively.

Both A and B maintain their state of rest if Ca and Cb maintain their original position – Undisturbed state

Both A and B lose their state of rest if Ca and Cb loss their original position respectively - Disturbed state

Now, assume A is disturbed and moves with velocity V while B is undisturbed. Following is one of the possible conditions when A collides with B.

A pushes B in front of it in its original direction of momentum until both gains V1.

Here B never offers any resistance to A rather it takes the momentum from A – total momentum of the system still remains the same. Let "a" and "b" are the jitters/impulses (shock waves) produced within A and B respectively due to their collision. Cb shifts away from its original position when “b” passes through it, which makes B unstable. Similarly, Ca also shifts towards its original position when “a” passes through it, which makes A less unstable than before.

Although both A and B osculate (juxtaposed) each other but exert no further force on each other after when both masses attains V1. Both Ca and Cb off center, therefore, A is under reduced momentum of while B gained a momentum.

A or B spins if the line action of "a" and "b" are truncated – not passes through the centroid.

Push or pull is considered a force. A pushes B due to its momentum, therefore, momentum is a Force F.

So force which is a push or pull depends upon on both moving mass and its final velocity, not acceleration.

Addendum: It is said all the laws of physics remain the same in every inertial frame if moving with constant speed. This is true only if the inertial frame is moving in earth’s (or any other celestial’s) atmosphere due to its smooth ride on equipotential lines (same elevation).

No celestial gravity’s atmosphere means no smooth ride on the equipotential lines of gravity and hence all the objects in a spaceship if not attached to each other are considered individual object including spaceship.

Therefore a person (if not fasten) in a spaceship and a spaceship are two different objects in space therefore initially when a spaceship accelerates from rest and then gains constant speed, all objects (if not attached to the spaceship) within the spaceship are still at rest. This means the back of the cockpit moves towards a person who is still at rest while the front of spaceship moves away from the said person. Finally, the rear cockpit reaches a person and a person is pushed by the rear cockpit in forwarding direction of the spaceship when it catches/hit a person.

So the above statement might not hold true for space due to the lack of celestial gravity. — Preceding unsigned comment added by 2001:56A:739C:D300:2503:4AE4:B7:5558 (talk) 19:04, 21 April 2019 (UTC)

For any object in space – considering gravity

As said, it is the gravitating mass, due to which a falling mass shows resistance because of its weight against another force, therefore the heavier the mass the greater will be its gravity or resistance due to gravity (all particles of the object fall towards the c.o.m of that object) or the greater the mass the greater the force will be required to displace its c.o.m, therefore, a tiny apple can’t change the strategic position of c.o.m of earth.

The c.o.m of falling mass is below its original position while the c.o.m of flying object is above its original position

The collision effect of the aforementioned A and B depends upon the size, shape, density, and velocity, etc therefore both "a" and "b" may or may not reach the center of mass of A and B respectively. The two outer particles of A and B, which collide with other, start exerting a force on the neighboring particles, the said neighboring particles pass "a" or "b" to the next connected particles closely and so on and this is how shock wave passes through A or B.

Both "a" and "b" depend upon the mass below, above, right, left, back and in front and how their elasticity or interlocking system etc is.

It is said that all objects fall at the same rate if this is true then why the damaging/penetrating effect of the same mass is different if fall (at the same rate) from different heights on the ground.

This means force is directly proportional to the mass of the falling object and its final velocity (not acceleration)

Therefore Force F = MV but not F = ma or mg where g=GM/d^2 or 9.8 m/s/s.

Similarly, addition (unless totaling) or multiplication of two or more things of different types (e.g. goats and trees) has no useful meaning in mathematics, therefore, I don’t understand why mass and velocity (or ma) are in the multiplication form in the formula of momentum. For Example

We get the following when 3 goats are multiplied with 5 trees

= 3 (goats) x 5 (trees) = 15 goat.tree

Likewise, the momentum of a mass of 3 kg when moving with a velocity of 5 m/s can be calculated as follows

Momentum = mv = 3 (kg) x 5 (m/s) = 15 Kg.m/s

Although we are so used to with kg.m/s and others similar multiplication in science that we accept them religiously but to be very honest, both goat.tree and kg.m/s, etc have no useful meaning - (m/s has meaning).

Why not momentum = M+V if the multiplication of MV is allowed. And the same is applied to all similar mathematical equations.

Anyway, shouldn’t force be measured relative to the displacement of c.o.m of moving mass as explained above and or indirectly via relative to standard penetration on the ground or any standard surface? 2001:56A:739C:D300:6144:2EAE:B584:322A (talk) 04:01, 7 April 2019 (UTC)Eclectic Eccentric Kamikaze

  • Inertia is not "resistance". In the idealised "Newtonian pool table" that we're taught at school there is no "resistance" (i.e. no friction) as this would make things too hard to comprehend. However there is still inertia and gravity.
An object of any mass (continuous) irrespective of size can be pushed or pulled without any resistance - Right? is true if there's no resistance, i.e. there's inertia, but there's no friction and no gravity acting upon it in the direction of movement. So in the simplest case, "an ant can push the Earth", just very, very slowly.
You have to be very careful with terminology here. "Inertia" is inertia, not resistance. "Momentum" is momentum, not force. It might give rise to a force, or more carefully worded it might give a force for a limited time, or it might give rise to an impulse. But to say therefore, momentum is a Force is just wrong (that "is" implies a definition, not just a correlation) and thinking that will make all your subsequent reasoning go adrift. Andy Dingley (talk) 10:07, 7 April 2019 (UTC)

You may be right but inertia is a resistance according to the a definition of Wikipedia. Neither an apple nor earth shows resistance when they feel the same amount of force pulling each other together. its just a proposal. — Preceding unsigned comment added by 2001:56A:739C:D300:6D17:A780:4BAC:2A63 (talk) 19:43, 7 April 2019 (UTC) So if an object of any mass (continuous) irrespective of size can be pushed or pulled without any resistance (true - you said) then this means all objects of different masses can be accelerated at the same rate with the application of the same amount of force. — Preceding unsigned comment added by 2001:56A:739C:D300:7CC1:E023:1A7:BE51 (talk) 14:36, 10 April 2019 (UTC)

Newton didn't first proposed laws of motion[edit]

Kanada (Indian philosopher) had first described laws of motion in Sanskrit (Ancient Indian language) around 600 BCE.

This has been recently verified too.

This should be updated 2409:4064:2211:7794:541C:1972:FB76:2CE6 (talk) 15:02, 12 July 2019 (UTC)

  • Source?
Also, he didn't invent "Newton's laws of motion". Nor has anyone ever claimed that "laws of motion" of motion were Newton's invention. Even at Newton's time there were other theories for this, such as impetus. However's Newton's were the ones which worked.
AIUI, Kanada had a number of interesting theories, although there's very little known about his personal life, including an uncertainty over his date of nearly 500 years! So even though many of his theories, which overlap with Classical Greek thought, may be original and might even have influenced the Greeks, it's pretty certain that the Greeks had these ideas long before him and he may even have been influenced by the Greeks himself. His "four atoms" theory of classical elements is widespread throughout the ancient world and Aruni, another Vedic thinker was much earlier than Kanada.
His mechanics though, as much as I've read, was non-Newtonian. He had a concept of 'mass' and of 'weight' and gravity (I don't know how clear his distinction between them was), but he did not make Newton's connection to inertia. His thoughts on motion were thus like the impetus theories: the impelling force was related to the velocity, not (as Newton realised) to the change in velocity, i.e. acceleration. Andy Dingley (talk) 15:59, 12 July 2019 (UTC)
I agree with Andy Dingley. Newton’s Laws of Motion, published in 1687, were founded on the excellent work of Copernicus (1543), and subsequent work by Galileo, Johannes Kepler, Tycho Brahe and others. Newton’s Laws were effectively the result of collaboration of a number of leading thinkers and writers from 1543 until Newton’s time. I don’t doubt that prior to 1543 others speculated on the nature of motion but those speculations are not in the same class as the collaboration that led to Newton’s Principia. Dolphin (t) 23:08, 12 July 2019 (UTC)

Reply to user:Dolphin51

You should start reading properly. I hadnt said that kanada had INVENTED.

Source is Internet archive- Link of his 36 volumes-

Lines from his VOLUMES-

वेगः निमित्तविशेषात कर्मणो जायते | Translation : Change of motion is due to impressed force. (The law stated that an object at rest tends to stay at rest and an object in motion tends to stay in motion with the same speed and in the same direction unless acted upon by an unbalanced force.)

वेगः निमित्तापेक्षात कर्मणो जायते नियतदिक क्रियाप्रबन्धहेतु | Translation : Change of motion is proportional to the impressed force and is in the direction of the force.

वेगः संयोगविशेषविरोधी | Translation : Action and reaction are equal and opposite.

AND THIS IS PRESERVED IN ENGLAND. And he PROPOSED this even if with the uncertainty of 500 years then it is (600BCE + 500 years) or (600BCE - 500 years)

Even if we go against kanada then too its about 100BCE. Still before than NEWTON. And what role do personal life plays here? And there is no proof or pointing evidence that Greeks had first discovered


This confirms that kanada did proposed earlier than newton So this article needs an update. — Preceding unsigned comment added by Unitorimus (talkcontribs) 14:58, 13 July 2019 (UTC)