A question for you science guys

[bull]

If Newton's Third Law is true on all fronts (For every action there is an equal and opposite reaction) wouldn't there be such a thing as perpetual motion, which defies the laws of thermodynamics?

[Brock Samson]

Hummm...?
except for...
inertia...
gravity....
friction...

...and then there's the inevitable "Dissipation of Energy"..

in ·er ·tia      ( P )   Pronunciation Key   (-nûrsh)
n.
Physics. The tendency of a body to resist acceleration; the tendency of a body at rest to remain at rest or of a body in straight line motion to stay in motion in a straight line unless acted on by an outside force.
Resistance or disinclination to motion, action, or change: the inertia of an entrenched bureaucracy.


--------------------------------------------------------------------------------
[Latin, idleness, from iners, inert-, inert. See inert.]
--------------------------------------------------------------------------------
in ·ertial adj.
in ·ertial ·ly adv.

Source: The American Heritage ® Dictionary of the English Language, Fourth Edition
Copyright  © 2000 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.


in ·er ·tia (-nûrsh)
n.

The tendency of a body to resist acceleration; the tendency of a body at rest to remain at rest or of a body in motion to stay in motion in a straight line unless acted on by an outside force.
Resistance or disinclination to motion, action, or change.


Source: The American Heritage ® Stedman's Medical Dictionary
Copyright  © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.


Main Entry: in ·er ·tia
Pronunciation: in-'&r-sh&, -shE-&
Function: noun
1 a : a property of matter by which it remains at rest or in uniform motion in the same straight line unless acted upon by some external force b : an analogous property of other physical quantities (as electricity)
2 : lack of activity or movement â€"used especially of the uterus in labor when its contractions are weak or irregular


Source: Merriam-Webster's Medical Dictionary,  © 2002 Merriam-Webster, Inc.


inertia

n 1: a disposition to remain inactive or inert; "he had to overcome his inertia and get back to work" [syn: inactiveness, inactivity] [ant: activeness] 2: (physics) the tendency of a body to maintain is state of rest or uniform motion unless acted upon by an external force


Source: WordNet  ® 2.0,  © 2003 Princeton University

[bull]

So Newton's Law doesn't address that?

[Brock Samson]

For every action there is an equal and opposite reaction

is the inital action unending?... perhaps Bull you've stumbled (tripped over?) the secret of the universe!! 

[Headrope]

For Newton's Law to remain true there would have to be an opposite reaction to perpetual motion.

[Todd Wilson]

So why do I have wood in the morning?


Todd

[Shakey]

So why do I have wood in the morning?


Todd

As I started reading this thread Ithought to myself - too intense for a Sunday night!

[Charger_Fan]

So why do I have wood in the morning?

Viagra abuse.

[bull]

For every action there is an equal and opposite reaction

is the inital action unending?... perhaps Bull you've stumbled (tripped over?) the secret of the universe!!  

The initial action is always slowed when friction is introduced so there can't be perpetual motion, and that would seem to disprove Newton's law as it relates to motion. I don't claim to understand all this but I was just thinking of that law and how it doesn't make total sense to me. The only thing I stumbled on was a dirty shirt on my way to the bathroom.

[Chargerguy74]

You'd have to eliminate friction completely, gravity could be a problem, depends on the design.

[Lowprofile]

Um, my head hurts!

[Mopar440+6]

If Newton's Third Law is true on all fronts (For every action there is an equal and opposite reaction) wouldn't there be such a thing as perpetual motion, which defies the laws of thermodynamics?

So Newton's Law doesn't address that?

First of all Newton's Third Law states "When two bodies interact, the forces on the bodies from each other are always equal in magnitude and opposite in direction. " (Halliday, Resnick and Walker "Fundamentals of Physics" 7th ed.) Laymans terms, An object at rest will remain at rest and an object in motion will remain in motion unless an OUTSIDE force acts upon the object. In other words you would have to completely isolate the object from ALL outside forces, including but not limited to friction, gravity, air resistance, etc.

Secondly, the Laws of Thermodynamics deal with heat energy not motion.

[bull]

Thanks. That helps. What confuses me is the "equal and opposite reaction" portion of the law. It makes it sound as if the reaction, not the forces, are equal so when the objects interact their reaction would be equal and perpetual motion could exist. I know it doesn't exist and yet on the surface Newton's Law reads as if it could.

I was reading about thermodynamics and it's relation to perpetual motion here: http://www.kilty.com/pmotion.htm

Perpetual Motion and Thermodynamics
Thermodynamics developed from the analysis of machines and processes. Physicists and mathematicians have made it a rigorous science, but its axioms derived from hundreds of years of experience.

Physicists and engineers view perpetual motion precisely and abstractly. In fact, they view the idea of "machine" so abstractly that machines or processes or signals or even algorithms fit the definition. To them any machine violating one of the laws of thermodynamics is a perpetual motion machine. They classify a perpetual motion machine by which law it violates. So a machine violating the first law of thermodynamics is a perpetual motion machine of the first kind. Machines violating the second law of thermodynamics are perpetual motion machines of the second kind, and so forth.

There are very few ideas in physics important enough to call laws. The four laws of thermodynamics are especially important and useful. At one time I examined patents for an industrial company. The question I had to answer was..."will this process or that machine work? Should we buy this patent?" Most machines or processes are too complex to analyze directly in a short time. However, the laws of thermodynamics apply to their operation and make them much simpler to analyze. The analysis begins by abstracting the machine or process to its inputs, losses, and outputs. Then it is simple to apply the laws of thermodynamics to it; and if the machine violates one of the laws, we can send the patent back to the inventor with a polite thank you.

more...

[Ponch ®]

Secondly, the Laws of Thermodynamics deal with heat energy not motion.

someone correct me if im wrong (I slept through chemistry and physics class in high school), but motion at the molecular level is regulated by temperature. or maybe its the other way around. my point is, thermodynamics do deal with motion.

thermo=heat    dynamics=motion.

[AdamMopar]

Not Quite

Thermodynamics

Thermo - Heat
Dynamics - Force

Close though.

I guess I don't quite understand where you are not following his law.  Newton's third law realates the forces that two different bodies have on each other.  The third law by itself tells you nothing about the motion of the two bodies.  Just pretend you are pulling on a box with a rope.  You are pulling the box towards you.    And just to keep it simple use the "massless" rope.  If you break it apart into free body diagrams you will see the force of you on the rope is equal and opposite the the force of the rope on you and so on until you get to the box.  That gives absolutely no information about who the box or you move.

The only forces that affect the motion of a body determine how it moves. Newton's third law will only help you determine what these forces are.

If you have any particular questions I would be happy to give more information

Also there are plenty of people who abuse these laws, and the laws of thermodynamics as well  because they don't understand them.  Adam

[bull]

I have only a cursory knowledge of the law, that's why I brought this up as a question. Like I said just reading the law as Newton wrote it, without any analysis or commentary, it appears to say something other than what it really means. I don't presume to be on Newton's level, I just wanted some clarification.

[Mopar440+6]

I have only a cursory knowledge of the law, that's why I brought this up as a question. Like I said just reading the law as Newton wrote it, without any analysis or commentary, it appears to say something other than what it really means. I don't presume to be on Newton's level, I just wanted some clarification.

Bull, The point that was implied in AdamMopar's post and that I was trying to get at in my last post is that the "equal and opposite reaction" version of Newton's Third Law is not the actual textbook definition of the law. This is a shortened version of the law put into simpler terms. Thus for this version yes, it may appear to say something other than its true meaning but if you read the actual texbook definition of Newton's Third Law its meaning will be very clear...

[Ponch ®]

I have only a cursory knowledge of the law, that's why I brought this up as a question. Like I said just reading the law as Newton wrote it, without any analysis or commentary, it appears to say something other than what it really means. I don't presume to be on Newton's level, I just wanted some clarification.

Bull, The point that was implied in AdamMopar's post and that I was trying to get at in my last post is that the "equal and opposite reaction" version of Newton's Third Law is not the actual textbook definition of the law. This is a shortened version of the law put into simpler terms. Thus for this version yes, it may appear to say something other than its true meaning but if you read the actual texbook definition of Newton's Third Law its meaning will be very clear...

blah....you're just an arrogant 19 year old who knows nothing about life, so screw you and your fancy book learnin'. The laws of physics be damned!......

[Vainglory, Esq.]

I don't care what you read in a textbook.  Reams of textbooks won't make me feel any different (because it's feelings and not reality that apparently make the difference).

[bull]

Textbooks are so '90s anyway.

[dodgecharger-fan]

The problem with perpetual motion machines is that their concept implies that the energy to make them work is self generated.

Well, the initial action/reaction can be imparted on the machine but everything else after that must come from itself. Any outside force would be an expediture of energy of some sort and therefore negate the "perpetual" nature of the machine.

The reason(s) that it doesn't work as mentioned above - inertia, friction, the effects of gravity all suck energy from the system.
That leaves less energy to put back into the machine which results in less energy back out which is further reduced by inertia, friction and the effects of gravity. Eventually, the whole thing just degenerates itself like an '06 Charger thread.   

More than one of the laws of physics are in play - they just end up working against each other in this case.