Inertia

[Silvertiger]

Unstable, I'll try to explain it a different way. Imagine a car in a weightless environment in a static air atmosphere. Given enough time, a bug could push the car. Yes, it would take a LOT of time, but the car begins accelerating as soon as the bug begins beating its wings. (And yes, it would eventually reach a snail-crawling terminal velocity once the wind resistance is equal to the force exerted by the bug against the car, which would continue to accelerate up until that point.) That case is entirely provable. Maybe not with a bug per se, as a bug would probably just land and do nothing lol. (Even then, just by landing, the car would move, imperceptibly.) But if you attached an itty bitty electric motor to the car with a very tiny fan and turned on the motor, the car would begin moving and would thus accelerate.

Any force applied, no matter how small, will move any object provided that the object being pushed is not applying a force of its own accord in direct linear opposition (resistance). (Now, where I come from, things don't move by themselves.) If there were any resistance of any kind, then how could the car move? All we are talking about here is time. If you want to call time a resistance, then that would be more accurate. Without time, acceleration would not exist, and every thing, once a force was impressed, would move to another position instantaneously. Inertia therefore remains simply an absence of an input or transfer of external energy.

You can also look at inertia in this context as the opposite of energy. If energy is the capacity to do work, E=Fd/t, then inertia is the capacity (tendency) to do nothing (remain doing whatever you are doing without change.)

And yes, F=ma is the current inertial representation for mass, as it states that for a given force, a greater mass will accelerate less than a lesser mass. This is understandable, as there is a tradeoff...but, in either case, are either accelerations being resisted? No.

Example 1: With a Force of 10 Newtons, a 10kg mass can be accelerated at 1m/s^2.

Example 2: With a Force of 10 Newtons, a 1kg mass can be accelerated at 10m/s^2.

For both examples: Was either acceleration resisted in any way? Nope. They were just different accelerations. There was definitely a tradeoff between mass and acceleration, but nothing was actually resisted. The force did what it was supposed to do for both examples, and neither energy exchange was resisted.

If you then choose to classify the force as an "effort," then that is a different story, as it would "feel" more difficult to push a semi than a car, which is a misnomer, because what you are really feeling is resistance from contact friction, a dissipative force in direct opposition to the force you are applying.

But I can tell you from experience that it is JUST AS EASY to push a semi as it is to push a car. Put me in a weightless room with my feet against a wall and my arms against the semi and I will move it without breaking a sweat. I could move it with one finger in that case. No problem. Heck, if it's on a level polished floor with rigid polished steel wheels I could move it. I have moved entire trailer bodies by hand. Easy to do when they are on wheels (dollies). A little more difficult when gravity is involved because of friction. So just imagine how easy it is to do in a weightless environment. This proves the case that nothing is being resisted. It just takes longer to change its state of motion based on its mass...time.

[Silvertiger]

I'm just outlining a potential hiccup in your guesswork Frank. I'm not dancing around a question that has been posed three different ways. I was very specific. If you choose to uphold this then you need to defend it as valid both mathematically and logically. You have avoided both because imo you either don't know how or you doubt your own work. Here it is again, put forward once again in another way: Your finger feels the strain naturally since it is a finger...does the wall also feel a strain of itself since the wall will not strain in the slightest against your finger?

I have been researching materials all my adult career and I can assure you that the wall will suffer a compression strain.

Frankly, I'm surprised, indeed shocked, that you don't realise this.

Still splitting hairs, huh? Keep at it and someone may go bald. :P Sheetrock is easy to strain. You would have to push really hard with your finger though. Do you think that if you pushed on a diamond that it would strain against your finger?

But, even so, in order to have a strain a force must be applied to cause it. More accurately though, if you push on a diamond and a diamond pushes back to where the force accelerations cancel out, you are left with potential energy, not strain. Even if the diamond imperceptibly deforms against your finger, it will settle into the strain position, and your "strain force" will have been spent. Let's just call it a spring, because at its core that is all strain is: elasticity versus rigidity of the molecular bonds. And when your "spring" is compressed to the max, the strain will have stopped, and the PE of both your finger and the diamond will remain. Strain is an effect Frank, not a cause.

[unstable]

To charge something of energy (of any kind, whether it is kinetic, electrical, hydraulic, magnetic .. etc) you need a source of energy and time.
Time is a parameter that certainly concerns the transfer of motion. What is opposed to impress the new motion, if we do not call it resistance we must call it "transfer process" ... certainly not "time" alone. Sorry but for me, your way of interpreting all this is absolutely illogical and wrong.

We remain of our different opinion and conclude this way.

[Silvertiger]

"What is opposed to impress the new motion?" Now you're saying that inertia is a resistance against a force. Sorry dude...only another force can resist a force. That's not opinion...that's fact. You seem to get the two confused. You don't even have an opinion because you keep changing your mind. Inertia is NOT resistance...neither is time. Things...just...take...time. That's all there is to it. It is what happens in the absence of a force.

How could I push a tractor-trailer with one finger if the action were being resisted by itself?

[unstable]

I do not understand if you pretend not to understand or you really are convinced of what you say.

It should be clear to anyone that the act of transfer of motion is perceived (but really it is) by the transferor of energy as a resistance and this during the whole transfer process, whether it is a Yoctosecond or a millennia. There are no doubts about it. You are trying to convince others to accept your wrong and inconsistent assumption. ;-)

Remaining on the electric example ... if we load a capacitor for a certain time interval (say 50 milliseconds), the power supply that supplies the necessary electricity "will see" a load to its output terminals that will have to "win" by supplying energy . If instead of the capacitor we put a pure resistor that has the same resistance curve (it is only an example) as the capacitive load, the power supply will have to deliver the same amount of energy. The difference is that in the first case it is not a matter of dissipative resistance, the energy spent was transferred and accumulated by the capacitor (Ignoring losses). In the second case it is dissipative, energy has been converted into heat by the resistor. Heat that, if not reused, is dispersed in the surrounding environment and then lost... but the power supply does not "see" this two different load at its output terminals. For it, however, it is the same action of opposition that must "win" by delivering energy. The same thing happens in the motion of the masses, by making the parallel with the mass motion inertia, the first case (capacitor) is the transfer of kinetic energy to a mass in space. The second case (resistor) is the transfer of the same kinetic energy into a mass that dissipates it by friction (for example, a mass on the earth where gravity and air tend to create friction).

To imprint a change of motion to a mass, inertia must be overcome as long as it lasts, until the transfer of kinetic energy has been completed and this happens only thanks to the energy transferred/spent over time. During this time the mass opposes a resistance to the change of motion. If there is no friction it is not a dissipative resistance but this does not change things.

In conclusion, if there were no resistance for the entire time interval of kinetic energy transfer, we would succeed, in the absence of air and gravity, to move a train only by leaning a finger and this immediately... and instead it seems that it is not so... ... I wonder why :-))) You do not move a mass with the only time but providing energy for a certain time. The fact that it takes time is a clear sign that there is something (of an unspecified) that is opposing to the new motion ... this is inertia.

The mistake you make is to consider "resistance" as the impossibility of carrying out an action. It is not so. You make confusion with the words and give them an incorrect meaning.
If you need energy it's just to win the opposition to the change of motion ... if you do not like to call it resistance ok, but it's your problem. I call it (non-dissipative) resistance ... since for a certain time and always to a different extent it is an obvious "opposing force".

It seems so logical and clear to me that I really struggle to understand how you can not accept it.

[Senax]

@unstable

To be fair to Tiger I'm sure he is really convinced in what he says.

I understand his reluctance to give up his hold on nurse's hand and I sympathise.
To give him his due he has started a very interesting thread which gets down to the nitty-gritty of things.
In this type of thread it is important to come to a truce when one can see that one's assumptions and view of the world are irreconcilable and further discussion with a particular member will be fruitless.

At least we have managed not to bring Hitler into play. :-)

[unstable]

@Senax, Ok but if there is no comparison of ideas and views, even "ruthless" (without being vulgar), then it makes no sense to participate in a thread. :-)
I'm like him ... if I'm convinced I'm right, I do not give up.

May the strain be with you :) lol

Silvertiger, I have another good example ready (leave aside the details of the type that you have a fixed reference under your feet and you can breathe). This experiment could also be done on earth, with a heavy mass on a magnetic track and in a vacuum chamber.

Try to interpose a scale weighing people (or a dynamometer) between your pushing hand and a stationary (relative to you) train in space. Start pushing ... until your push continues following the mass that starts moving... why does the scale display a value of "weight" (is a people weighing scale) greater than zero ? for two reasons:
1) the pressure that the hand exerted on the weight scale interposed between the hand and the mass to be moved.
2) the resistance to the motion impressed by the hand , that, for the weight scale, determines a reference point for measuring what the scale makes us read as weight (a force). And yes, this is a manifestation of inertia !

(with an ironic tone) "But it is really strange that the scale marks the presence of a weight (a force) ... in addition to the pushing hand, on the other side there is no contrary force." LOL :-)))

Clearer than that...

[ME]

Silvertiger, this whole topic feels a bit messy. What's your current stance about Inertia exactly?

I agree with half of what you say, the other half is unclear...
You started with:
"Inertia is a resistance to a change in motion. This means that it falls under the purview of N3, as well as N1"
"2. Inertia is the reactive force against the net force " (Nope)
And: "and jnertia ks a function of time" (Nope)
And: "Inertia is a force, rendered as I=-Fr" (Nope)
Then: "You can also look at inertia in this context as the opposite of energy" (What's that? nope)
Then: "Now [Claudio] you're saying that inertia is a resistance against a force. Sorry dude..."" (Huh?)
Then: "Inertia is NOT resistance...neither is time. " (...)
Perhaps I missed something in between as there was a lot of noise.
I understand a change in opinion... but blame others? Seems unfair.

I had a few ideas as reply already: I'll prepare something. The Inertial effect is really simple...

[unstable]

Duplicated post... ops

[Silvertiger]

Silvertiger, this whole topic feels a bit messy. What's your current stance about Inertia exactly?

I agree with half of what you say, the other half is unclear...
You started with:
"Inertia is a resistance to a change in motion. This means that it falls under the purview of N3, as well as N1"
"2. Inertia is the reactive force against the net force " (Nope)
And: "and jnertia ks a function of time" (Nope)
And: "Inertia is a force, rendered as I=-Fr" (Nope)
Then: "You can also look at inertia in this context as the opposite of energy" (What's that? nope)
Then: "Now [Claudio] you're saying that inertia is a resistance against a force. Sorry dude..."" (Huh?)
Then: "Inertia is NOT resistance...neither is time. " (...)
Perhaps I missed something in between as there was a lot of noise.
I understand a change in opinion... but blame others? Seems unfair.

I had a few ideas as reply already: I'll prepare something. The Inertial effect is really simple...

You're right. I did change my mind...and thought that I had said as much lol. The more I thought about it, the more resistance did not make sense to me, and so I started over. I first began this thread based on the information that was already mainstream, and then deviated from there. I agree that we need common ground, and I will admit that there is something just...off...about the current definitions of inertia. Here is why I cannot look at it as resistance: because after a force has been impressed, an object's NEW state of motion does not diminish. I agree with unstable's statement that it involves a transfer of energy...and I had already said the same thing previously. I said that F=ma describes that tradeoff between mass and acceleration. And there is no resistance that exists between that trade. Given a force, a mass will determine its own acceleration, but will not resist that acceleration.

And yet, within the perspective that a greater force is now required to accelerate a greater mass at the same acceleration of a lesser mass, then one could say that it is resisting to me moved in the same fashion as the smaller mass. If this is a "resistance" then why use mass to describe it? Something is missing. Time has to fit in...somewhere. All other formulas include time, because it is a key player in ALL interactions, and that is the source of my continued confusion and curiosity lol. So it remains a work in progress for me. And I've actually been thinking about for a few years now but did not really avidly pursue it.

Hopefully that clears a few things up. :)

[Silvertiger]

@unstable

To be fair to Tiger I'm sure he is really convinced in what he says.

I understand his reluctance to give up his hold on nurse's hand and I sympathise.
To give him his due he has started a very interesting thread which gets down to the nitty-gritty of things.
In this type of thread it is important to come to a truce when one can see that one's assumptions and view of the world are irreconcilable and further discussion with a particular member will be fruitless.

At least we have managed not to bring Hitler into play. :-)

I haven't really made much progress with this. The only thing that I am currently convinced of is that time should be included in inertia if it is to be described as a resistance. At the same time, I do not actually see a resistance...just a trade.

[agor95]

Silvertiger

Been reading the thread - I is a good read.

Thinking of a good post in return.

Regards

[Senax]

@unstable

To be fair to Tiger I'm sure he is really convinced in what he says.

I understand his reluctance to give up his hold on nurse's hand and I sympathise.
To give him his due he has started a very interesting thread which gets down to the nitty-gritty of things.
In this type of thread it is important to come to a truce when one can see that one's assumptions and view of the world are irreconcilable and further discussion with a particular member will be fruitless.

At least we have managed not to bring Hitler into play. :-)

I haven't really made much progress with this. The only thing that I am currently convinced of is that time should be included in inertia if it is to be described as a resistance. At the same time, I do not actually see a resistance...just a trade.

I agree - absolutely.

[unstable]

"The only thing that I am currently convinced of is that time should be included in inertia"

I agree too.

[eccentrically1]

Mass and inertia have a relationship, but they don't describe the same thing. Inertia is a property, mass is the measurement of that property. It's further confused by the fact they use the same units of measurement, so there isn't a difference in their quantitative properties.

The resistance to +/- acceleration by an object may not be worded that way in Newton's law, but that is the implication, hence it's called the law of inertia.

So it's better to say the inertia of an object resists, rather than the mass resists. The 3rd law gives the relationship between the two objects in any interaction; equal and opposite. It's still the same relationship in a weightless and/or frictionless environment. So if I tried to push a car in space, I will accelerate away from the car, while the car barely accelerates away from me. If I push another person with the same mass, we accelerate away from each other at the same speed.

And to further confuse, equations don't include coefficients of frictions which can change the outcome of an interaction (on earth). If you hit a dimpled golf ball, it will have a different flight and acceleration than a smooth dimple-less golf ball because of the lift from the dimples, even though both golf balls have the same mass. In space, they would have the same flight and acceleration.