Newton's third law violations

[sciman55]

I know this would never happen in the real world, but I still have questions,

 

1. What would happen if the forces in Newton's third law were not equal and one object has more force than the other? Please give me an example.

 

2. What would happen if the direction of the forces in Newton's third law were not opposite, and the two objects go in a different direction (one force acts north, the other object acts west) Or the forces go in same direction? Please give me an example.

 

I know the conservation of energy would be violated, so don't say anything about momentum please.

[Tormod]

1. What would happen if the forces in Newton's third law were not equal and one object has more force than the other? Please give me an example.

 

Do you mean if one object excerts a higher (or lower) force than it should? That's fairly easy to explain. If the third law was violated, we could for example have rockets which could burn a little bit of fuel yet have strong acceleration (low force in, high force in the opposite direction). Or, if the opposite happened, you'd have to burn a LOT of fuel to generate a little push.

 

2. What would happen if the direction of the forces in Newton's third law were not opposite, and the two objects go in a different direction (one force acts north, the other object acts west) Or the forces go in same direction? Please give me an example.

 

This should be self-evident. If the forces do not go in opposite direction, then there are really only two options: either they always operate at the same angles (say at 67 degrees) or the angle could be random. If the first is true, then a rocket engine would have to be mounted so that it was tilted. If the latter is true, it would be impossible to build a rocket engine since the thrust could come in any direction and thus the rocket would not go in a straight line.

 

If the forces go in the same direction, you'd get some interesting results. Your rocket would have the engine in the front. Also, just a tiny push on things would make them move (if you kick a ball, it would go extremely far since the reactive force would act in unison with the original force). I think. :lol:

[sciman55]

This should be self-evident. If the forces do not go in opposite direction, then there are really only two options: either they always operate at the same angles (say at 67 degrees) or the angle could be random. If the first is true, then a rocket engine would have to be mounted so that it was tilted. If the latter is true, it would be impossible to build a rocket engine since the thrust could come in any direction and thus the rocket would not go in a straight line.

 

If the forces go in the same direction, you'd get some interesting results. Your rocket would have the engine in the front. Also, just a tiny push on things would make them move (if you kick a ball, it would go extremely far since the reactive force would act in unison with the original force). I think. :lol:

 

What exactly do you mean by all this? What do you mean about the reactive force acting in unison? What do you mean about the same angles and angles at random? How do they work again? What do you mean about the engine in front in the rocket? Could you explain that tiny push on things to make them move a little more?

[Turtle]

I know this would never happen in the real world, but I still have questions,

 

1. What would happen if the forces in Newton's third law were not equal and one object has more force than the other? Please give me an example.

 

2. What would happen if the direction of the forces in Newton's third law were not opposite, and the two objects go in a different direction (one force acts north, the other object acts west) Or the forces go in same direction? Please give me an example.

 

How do you "know" this or that wouldn't happen in the "real" world? Why not give your "example" rather than send us all fishing (for something that doesn't exist?).

In the preface to Principia, Newton said this in regard to the seeming paradoxes in his following laws of motion:

For I am induced by many reasons to suspect that they may all depend on certain forces by which the particles of bodies, by some causes hitherto unknown, are either mutually impelled towards each other, and cohere in regular figures, or are repelled and recede from each other; which forces being unknown,

philosophers have hitherto attempted the search of Nature in vain. Issac Newton - Principia

 

Einstein further says this:

There is no way to distinguish the effects produced by the inertial force of acceleration (a pushing/repelling force) from the effects produced by gravitational force... Albert Einstein

 

(the above constitute quotes of quotes of quotes; employ due diligence in establishing their veracity.)

[Tormod]

What exactly do you mean by all this? What do you mean about the reactive force acting in unison? What do you mean about the same angles and angles at random? How do they work again? What do you mean about the engine in front in the rocket? Could you explain that tiny push on things to make them move a little more?

 

I answered your original questions. I don't understand your new questions. I explained what would happen and gave you examples.

[sciman55]

Could you explain it more cleary, please?

[Tormod]

Could you explain it more cleary, please?

 

What exactly don't you understand?

[sciman55]

I understand the part about forces in magnitude, but I am confused about what you said about force not being opposite in direction. Could you explain the direction part, but more clearly? More importantly,

 

If the forces go in the same direction, you'd get some interesting results. Your rocket would have the engine in the front. Also, just a tiny push on things would make them move (if you kick a ball, it would go extremely far since the reactive force would act in unison with the original force). I think. :lol:

 

What exactly do you mean by unison?

[Tormod]

I understand the part about forces in magnitude, but I am confused about what you said about force not being opposite in direction. Could you explain the direction part, but more clearly?

 

The third law of motion is really fundamental: Every action has an equal and opposite reaction.

 

So what I am saying is that if there is a violation of Newton's third law, it would mean that the opposite reaction would change. It could change in two ways:

 

1) the reaction would not be opposite but point in a different direction (this is why the rocket engine would have to be mounted in a tilted position, in order to offset the change in direction).

 

2) the reaction could come in a random direction, which means that we could not predict which direction it would be. thus a rocket engine would have no effect, or rather, the rocket would move all over the place.

 

 

More importantly, What exactly do you mean by unison?

 

You asked "what if the forces act in the same direction". Unison means (here) that they act in the same direction.

[Buffy]

2) the reaction could come in a random direction, which means that we could not predict which direction it would be.

Actually when I was originally contemplating this thread and trying to come up with alternatives the thing that popped into my head was not that it would be random (which is indeed the logical opposite of "opposite direction") but rather that it would be at some fixed different angle, say 37 degrees, which brings up some interesting geometrical problems. Imagine playing billiards with a fixed offset that you'd need to put into your eyeballing of where the balls would all go...

 

Thinks differnetly,

Buffy

[sciman55]

I need more explaination. If the two forces are in the same direction, why would

the engine be in front of the rocket and why would a tiny push make things move? Also, new question, what would happen if newton's second law were violated?

[Turtle]

___Some further thought on this brings to my mind Peaucellier's linkage, which is a real physical/mechanical device consisting of six arms linked by five axles (points of rotation). The following Wikpedia article gives a diagram of the linkage, although it poorly describes the linkage's action in my opinion.

http://en.wikipedia.org/wiki/Peaucellier-Lipkin_linkage

 

___The linkage, just like a pantograph, works as a drawing device, but whereas a pantograph scales (enlarges or shrinks) a line drawing without changing the angles, Peaucellier's linkage "inverts" the lines in a drawing. In the use of both linkages, one vertex is fixed to the drawing surface & a pencil/pen is placed at another vertex & bears on the drawing surface; moving a stylus on a 3rd vertex to trace a line already drawn results in the linkage drawing a new line.

___In regard to Newton's Third Law then, with Peaucellier's linkage the "inverse" or "opposite" of a straight line is a segment of a circle, i.e. a curved line. On the face of it then, it seems erroneous to think "opposite" is always a straight-line function as in the rocket engine examples.

___Well, something to seriously think about.:lol:

[Tormod]

Imagine playing billiards with a fixed offset that you'd need to put into your eyeballing of where the balls would all go...

 

That is pretty much how I play. :lol:

[Tormod]

I need more explaination. If the two forces are in the same direction, why would

the engine be in front of the rocket and why would a tiny push make things move?

 

Newton's third law: Every action causes an equal and opposite reaction. So by putting a rocket engine at the BACK of a rocket, any exhaust coming out of it helps boost the rocket in the FORWARD direction. Ok?

 

Now, if the reaction was opposite, like you asked in the first post, then imagine what would happen. The reaction would no longer push in the opposite direction, but in the SAME direction that the rocket is going. Thus you would have to put the engine at the front of the rocket, mounted so that it burns in the direction of motion.

 

Also, new question, what would happen if newton's second law were violated?

 

Start a new thread. This one is for third-law-violations, dizzying enough as it is.

[sciman55]

Another question; if Newton's third law were not equal in magnitude when two objects of unequal mass collide, how would the unequal forces of the two objects deal with the unequal masses?

 

Also, how would forces unequal in magnitude affect running, pushing, lifting, throwing, jumping, stretching, squeezing and breaking things?

[kamil]

Another question; if Newton's third law were not equal in magnitude....

 

 

This question doesnt make much sense.

If they werent equal in magnitude? So if the we pretend there's a Universe where these laws dont exist, then what laws replace them? Its like saying 'We're gonna play soccer, but there arent any goals, so who do you fink will win?'

[CraigD]

Another question; if Newton's third law were not equal in magnitude when two objects of unequal mass collide, how would the unequal forces of the two objects deal with the unequal masses?

 

Also, how would forces unequal in magnitude affect running, pushing, lifting, throwing, jumping, stretching, squeezing and breaking things?

This question doesnt make much sense.

If they werent equal in magnitude? So if the we pretend there's a Universe where these laws dont exist, then what laws replace them? Its like saying 'We're gonna play soccer, but there arent any goals, so who do you fink will win?'

kamil is correct – one can’t effectively answer a question like “what would happen given these initial conditions if these (Newton’s) laws of physics did not apply?” Before one can begin to answer, one has to make up precise replacement laws, then ask “what would happen if these alternate laws applied?”

 

Although such an exercise isn’t useful in predicting or explaining how the actual universe behaves, it can be useful in learning how to calculate mechanical systems in a formal manner. Since your intuition about real-world objects may be almost completely useless under the alternate laws, the temptation to “fudge” your formal calculations with intuitive hunches is reduced.

 

To continue this line of thought on a solid footing, Sciman55 or someone else interested in this could write the formulae of some mechanical laws different than but usable for the same calculations as Newton’s laws of motion, then applying them to some scenarios.