Homework help - Models.

[Endy0816]

I thank you for your considerable patience and trying to explain, but I can not see any other force except gravity been involved, and have still no idea what force Fn is trying to represent.

 

Now if you explained Fn has a weight shift on a molecular level of the object that was ''sliding'' down a hill, then I think I could understand that.

 

It is due to gravity...

 

If you want the simplified version it is that force which keeps an object from going through whatever it happens to be resting on.

 

Ask yourself though or do a test on what happens if you flip a scale upside down and then stand on it. Now that you are on the bottom of the scale and the Earth is on top, what reading for force does your scale provide you?

Edited September 10, 2014 by Endy0816

[Relative]

 

It is due to gravity...

 

If you want the simplified version it is that force which keeps an object from going through whatever it happens to be resting on.

 

Ask yourself though or do a test on what happens if you flip a scale upside down and then stand on it. Now that you are on the bottom of the scale and the Earth is on top, what reading for force does your scale provide you?

The weight of the scales,

 

I do not get it , and I am still thinking models by the way, I thank you I am learning a lot about models believe it or not.

 

I will quote this I wrote on other science forum with some replies,

 

me-''So all you so called clever types, if f=ma , how is the ground accelerating away from gravity, because that is what you are saying.

 

You say the ground gives of a force that is equal to the block, Fn, so how is the ground accelerating the opposite to gravity?

 

stop talking garbage''

 

reply- ''the F in F=ma is the resultant force - so once all the components of all forces in the same direction have been considered and added up, what's the force left over, and that is what drives acceleration.

The ground is not "accelerating away from gravity".

 

me-''So you admit then that the ground is not accelerating away from gravity, so the force is directional towards gravity yes?

you have just agreed with me.''

 

 

 

To have an opposing force we have to have f=ma in the opposite direction of each surfaces.

[Fuzzwood]

Masses attract. If you are pulled towards the earth, the earth is just as much pulled towards you. m_earth*g_you = m_you*g_earth.

[Endy0816]

 

One scale with the bulk of one human test subject on the opposite side.

 

Note: Previous attempt made with nonhuman test subject, test subject fled. Retesting with subject not recommended.

Edited September 11, 2014 by Endy0816

[Ophiolite]

Relative, this is the point where you make a post such as this:

 

"But did you take this photo before or after you have your daily bowel evacuation? Surely that would make a difference."

 

I hope you can see, through this example, how pointless it is when you introduce irrelevancies. You are making progress. Eliminate the irrelevances and you will move even faster.

[Relative]

Masses attract. If you are pulled towards the earth, the earth is just as much pulled towards you. m_earth*g_you = m_you*g_earth.

Only if you believe that one house brick is attracted to another house brick which I do not.

 

And is it not that all matter would be attracted to the stronger Force?

 

The stronger force been the core!

 

So how would our feet attract the ground, if the ground is been attracted directionally by a greater force?

 

I am sorry , I think I may never understand your model , and the sliding block down an incline, that has a Fn, friction and gravity of forces.

 

For me to believe the Fn part, you would have to prove to me that two house bricks have attractive force towards each other!.

 

I do not see any force in an house brick, except its weight.

 

An house brick has no center of gravity like an Earth's core.

 

And has far has I know, neither is a house brick magnetically or electrically charged, although a house brick has thermodynamics , and takes on heat from surrounding energies/atmosphere.

 

One scale with the bulk of one human test subject on the opposite side.

 

Note: Previous attempt made with nonhuman test subject, test subject fled. Retesting with subject not recommended.

I do not understand what you are trying to show, are you trying to show a set of scales on some ones head upside?

 

 

Or are the scales upside down and someone standing on what would be the actual bottom, but in this instant the top.

Thinking about a set of scales, that has to be recalibrated in different areas of the planet.

 

I set the scales on zero, then stand on them, I am falling at x amount of pounds.

 

You can clearly see body weight force is equal to falling.

Edited September 13, 2014 by Relative

[Endy0816]

Only if you believe that one house brick is attracted to another house brick which I do not.

 

And is it not that all matter would be attracted to the stronger Force?

 

The stronger force been the core!

 

So how would our feet attract the ground, if the ground is been attracted directionally by a greater force?

 

I am sorry , I think I may never understand your model , and the sliding block down an incline, that has a Fn, friction and gravity of forces.

 

For me to believe the Fn part, you would have to prove to me that two house bricks have attractive force towards each other!.

 

I do not see any force in an house brick, except its weight.

 

An house brick has no center of gravity like an Earth's core.

 

Yes, your standard house brick does attract other bricks. Your mass attracts my mass, our mass attracts other masses.

 

You can directly calculate this yourself.

 

F_Gravity = (Gm₁m₂)/r²

 

likewise

 

F_Gravity = m₁g₁

 

F_Gravity = m₂g₂

 

Because gravity is weak, the force your bricks or even you produce is typically weak, but it is also very real.

 

The Earth's mass is nothing special, there is just much much more of it relative to what is typically around us.

 

You may want to look at the Cavendish Experiment. The man measured what you claim doesn't exist. In doing so he basically found G. With G, your weight and the Earth's radius you can find the mass of the entire planet.

 

 

Or are the scales upside down and someone standing on what would be the actual bottom, but in this instant the top.

 

Yes, from the standard perspective the scale is upside down resting upon two chairs. From the flipped perspective, the Earth is resting upon two chairs which are themselves upon a scale.

 

Now according to the scale there is a force pushing up on it. That would be the Normal Force. If you want to look at it another way, you can say that the two masses are attracting each other. That too is valid and in my mind, easier to understand.

 

 

You can pretty easily prove that forces come in pairs for yourself. If you can stand on something that rolls, toss something with a decent mass away from yourself, you will see yourself move in the opposite direction.

 

The force you exert will equal the force exerted upon you. Forces balance out, this includes gravity along with the rest of the forces out there.

 

I find actual experimentation to work better than trying to build models. You actually test it and you don't need to take anyone's word for it or hit the "I believe" button. You'll know something to be true or not.

Edited September 14, 2014 by Endy0816

[Fuzzwood]

Only if you believe that one house brick is attracted to another house brick which I do not. <-- believing has nothing to do with the laws of physics. Those even work if you don't exist.

[Ophiolite]

Only if you believe that one house brick is attracted to another house brick which I do not.

If you still believe this after all this discussion then you should abandon science and take up basket weaving. That is not a trite comment, but genuine advice.

[Relative]

If you still believe this after all this discussion then you should abandon science and take up basket weaving. That is not a trite comment, but genuine advice.

Well, if the Cavendish experiment was done with equal dimension house bricks, and not lead balls, I would then maybe believe it, although I am unsure the Cavendish experiment is a fare test, due to the test been in an already gravity effected environment.

 

 

And gravity of the Earth having effect on the lead balls, both balls want to fall, both balls experience a downwards force.

 

And the twist of the wire, is no more than the twisting of water going down the plug hole.

 

''If you still believe this after all this discussion then you should abandon science ''

 

Well, science has not proved anything to me with 100% factual information and logic, there is no logic in all matter is attracted to all matter.

 

 

Similar to the Caesium clock, I can see the Cavendish experiment has another useless science invention, that misses all the parameters involved.

 

 

''I find actual experimentation to work better than trying to build models. You actually test it and you don't need to take anyone's word for it or hit the "I believe" button. You'll know something to be true or not.''

 

Yes totally agreed, however the test must account for all the variables. Put two house bricks in space and I bet you that they do not draw towards each other.

 

I see it like this.

If all matter is attracted to matter then all matter would hit the Earth ,

 

 

?

[Ophiolite]

http://www.jonsbushcraft.com/basicbasket.htm

[Fuzzwood]

@ your last picture: inverse square law, and orbital mechanics.

[Relative]

http://www.jonsbushcraft.com/basicbasket.htm

It says the link not there sorry, could you copy and paste what it says please?

@ your last picture: inverse square law, and orbital mechanics.

In orbital mechanics, the orbits are explained has,

 

If I put a chain on a rocket ship and attached the other end to a pole, and launched the rocket at X velocity, then the rocket ship will orbit around the pole.

 

 

Is that about right in my definition?

OK a new model for me to try - the asteroid belt.

 

Is the asteroid belt the event horizon equilibrium of gravity?

[Fuzzwood]

You won't need the chain. In an orbit, the kinetic energy with a vector along the velocity of the object will equal the gravitational or potential energy pointing to the mass at the center of the semimajor axis of the orbit. So the object is constantly falling towards the center of mass (and the center of mass towards the object) but the velocity and thus the kinetic energy is enough to keep the object in that particular orbit. Alos, changes in velocity will influence the orbit and if the velocity exceeds the escape velocity, the object will break orbit, or never enter an orbit to begin with as with your Hayley's comet. This does NOT mean that the vector of the comet is not influenced by the Earth's gravitational field.

 

 

(and before you ask: no that isn't me, but I can derive the equations as needed. Also, kerbal space program © is awesome.)

Edited September 14, 2014 by Fuzzwood

[Relative]

You won't need the chain. In an orbit, the kinetic energy with a vector along the velocity of the object will equal the gravitational or potential energy pointing to the mass at the center of the semimajor axis of the orbit. So the object is constantly falling towards the center of mass (and the center of mass towards the object) but the velocity and thus the kinetic energy is enough to keep the object in that particular orbit. Alos, changes in velocity will influence the orbit and if the velocity exceeds the escape velocity, the object will break orbit, or never enter an orbit to begin with as with your Hayley's comet. This does NOT mean that the vector of the comet is not influenced by the Earth's gravitational field.

 

 

(and before you ask: no that isn't me, but I can derive the equations as needed. Also, kerbal space program © is awesome.)

Thank you , my chain was to represent gravity. And I know if i cut my chain the rocket would accelerate away from the pole.

 

My problem is the elliptic orbit, I would expect an equal orbit.

 

R1 and R2 been of equal distance.

 

I do not know if you a have tried this, a piece of matter in a bath full of water with the plug took out travels an elliptic orbit around the plug hole.

 

This is because there is more force, nearer the plug hole side of the bath.

 

Meaning the ''side'' is closer.

Does the sun travel directional?

 

[imatfaal]

!

Moderator Note

 

RELATIVE - either get back to learning about basic models using simple Newtonian mechanics or we lock the thread. This thread will not be allowed to become a place for outlandish and completely erroneous claims.

 

Your failure to understand the normal, followed by a rejection of Newtonian gravity, and a cavalier disdain for some great Experiments does not bode well. Again remember that most of the people on this thread can use Newtonian mechanics to make testable predictions which barring typos and mathematical gremlins will be correct - your ideas will not.

 

So - get back to basic physical models or move to speculations. Homework help is not the forum for you to demonstrate your ideas of alternative physics - they do not work, are mathematically rubbish, and are easily shown to be false. You can learn physics or you can fool yourself - please choose the former

 

 

[Relative]

!

Moderator Note

 

RELATIVE - either get back to learning about basic models using simple Newtonian mechanics or we lock the thread. This thread will not be allowed to become a place for outlandish and completely erroneous claims.

 

Your failure to understand the normal, followed by a rejection of Newtonian gravity, and a cavalier disdain for some great Experiments does not bode well. Again remember that most of the people on this thread can use Newtonian mechanics to make testable predictions which barring typos and mathematical gremlins will be correct - your ideas will not.

 

So - get back to basic physical models or move to speculations. Homework help is not the forum for you to demonstrate your ideas of alternative physics - they do not work, are mathematically rubbish, and are easily shown to be false. You can learn physics or you can fool yourself - please choose the former

 

 

I am sorry I thought simple models where gravity, orbits etc, I am still doing models , but to make a model , I surely must understand the concepts first?

 

I can not understand where you get Fn from, why and how the ground pushes back, why would the orbit be an ellipse etc.

 

Again if you lock my thread, again I will go away and still not understand.

 

So again I will have to try find another forum to learn to understand.

 

I really want to understand, I do not want to see it another way, I want to see it how science see's it, but it is not my thought it does not tie into my logic and work.

 

I can not see the logic in it.

 

 

I thought the asteroid belt was a simple model, and passable has a model.

 

+energy = velocity, or minus energy = velocity.

 

Thermodynamics of their equilibrium orbit.

 

Is that not why the asteroids fly off?

 

 

And what do you mean -''rejection of Newtonian gravity, and a cavalier disdain for some great Experiments does not bode well.''

 

I have not rejected them,

 

 

I am asking why is not this way or that way, trying to understand where my logic is flawed and where you are correct.

 

I can easily go on wiki and get the exact current models and copy them , but I like to learn myself and consider things first for myself before I rediscover current.

 

Please do not close this thread, all forums do it, you can see I am not a troll and genuine trying to learn, although yes I agree I have a wicked imagination.

 

Do you want to know what I have learn about models?

 

 

I know a lot now, and understand what an actual model is, this forum has learnt me.

''Your failure to understand the normal'

 

I understand what science says , the normal , I understand where you get Fn from, but can not agree it is there, if all the forces add up to zero, then would we not float about, would we not feel our own body mass when we stand?

 

 

If I get past this Fn then maybe I will see it your way,

 

Let me clarify what you are saying, you are saying that the ground pushes back with a force equal to the weight opposing a force onto it?

 

 

To create a force F=ma , the ground is accelerating inwards, has no spring like properties, and no acceleration in the opposite direction.

 

 

To me all the force is inwards, and the ground compresses, uniaxial isotropic,

 

A question, if the ground pushes back, why is it that if I make a dent in soil using a hammer, the hole does not fill back up, if there is an opposing force f=ma from the ground, why does the ground not spring back into place?

And in the simple model of a block sliding down a hill, we have friction tag, Fn tag and gravity tag, why is there no air pressure/weight tag?

[Fuzzwood]

With a circular orbit you have equal radii for R1 and R2, and thus there is no exchange of kinetic for potential energy. The total energy of the system stays the same however. This is also the case in which R1>R2, e.g. an elliptical orbit. In this case there is a tradeoff between E_k and E_p. E_k starts to increase when a satellite moves from Apoapsis to Periapsis (points when the radius is the biggest (R1) or smallest (R2)), trading for E_p and increasing velocity, and vice versa when the satellite moves back to Ap from Pe.

 

To answer the post where you respond to the mod comment:

 

1) There are no thermodynamics involved as there is no significant heat exchange involved (as long as the meteor or whatever doesn't encounter the atmosphere that is). However you are correct in stating that such a system indeed has a certain total energy.

 

2) It is EXACTLY WHY you still feel your body mass that there is a normal force!. If there weren't a normal force you would be weightless! Not massless, mind you, but you would be weightless!

 

3) Your hammer indeed leaves a dent in the sand. It is not filled up because the moment your hammer leaves that dent that there is no normal force present to resist your hammer.

 

4) There is no air pressure tag because it is simply assumed that there is no friction of air in those models (again, not to overcomplicate stuff). Weight is already accounted for in the gravitational force. Mass is NOT weight. Weight is actually defined as F = m*a. So yes, everyone saying that they weigh a certain amount of kg is raping physics.

Edited September 14, 2014 by Fuzzwood

[Relative]

With a circular orbit you have equal radii for R1 and R2, and thus there is no exchange of kinetic for potential energy. The total energy of the system stays the same however. This is also the case in which R1>R2, e.g. an elliptical orbit. In this case there is a tradeoff between E_k and E_p. E_k starts to increase when a satellite moves from Apoapsis to Periapsis (points when the radius is the biggest (R1) or smallest (R2)), trading for E_p and increasing velocity, and vice versa when the satellite moves back to Ap from Pe.

That sounds complex, r1 and r2 on a ellipse , how is the Earth able to lag behind the sun as such and go away from the sun, what force makes the Earth draw back to the sun when the furthest away?

 

I know you will say gravity, so what explains moving away from the sun, If the orbit was circular, then I could easily see the orbital has been of the ball travelling around the pole theory, but with it been of ellipse, I can only see that the sun is moving and we lag behind at times?

[Fuzzwood]

No, I will say because of the kinetic energy that was gained from the exchange of potential energy. And I never stated such physics were simple. Oh, they are if you realize it is a simple matter of equalling E_k to E_p. 0.5 * m * v² = m * g * h, but filling in the variables with the correct values can sometimes be a chore.

 

In a circular orbit, velocity is a constant. In an elliptical orbit, the velocity is variable with a maximum at the closest distance and a minimum at the furthest distance assuming 2-body physics. The latter part means that I don't account for overcomplicating stuff like the moon or that the sun is orbiting something else. You should take something home from this: never overcomplicate physics if you can get away with an educated guess. This needs a quote.

 

https://www.youtube.com/watch?v=-E7h3vJXM08

Edited September 14, 2014 by Fuzzwood

[Relative]

With a circular orbit you have equal radii for R1 and R2, and thus there is no exchange of kinetic for potential energy. The total energy of the system stays the same however. This is also the case in which R1>R2, e.g. an elliptical orbit. In this case there is a tradeoff between E_k and E_p. E_k starts to increase when a satellite moves from Apoapsis to Periapsis (points when the radius is the biggest (R1) or smallest (R2)), trading for E_p and increasing velocity, and vice versa when the satellite moves back to Ap from Pe.

 

To answer the post where you respond to the mod comment:

 

1) There are no thermodynamics involved as there is no significant heat exchange involved (as long as the meteor or whatever doesn't encounter the atmosphere that is). However you are correct in stating that such a system indeed has a certain total energy.

 

2) It is EXACTLY WHY you still feel your body mass that there is a normal force!. If there weren't a normal force you would be weightless! Not massless, mind you, but you would be weightless!

 

3) Your hammer indeed leaves a dent in the sand. It is not filled up because the moment your hammer leaves that dent that there is no normal force present to resist your hammer.

 

4) There is no air pressure tag because it is simply assumed that there is no friction of air in those models (again, not to overcomplicate stuff). Weight is already accounted for in the gravitational force. Mass is NOT weight. Weight is actually defined as F = m*a. So yes, everyone saying that they weigh a certain amount of kg is raping physics.

exactly

[imatfaal]

I am sorry I thought simple models where gravity, orbits etc, I am still doing models , but to make a model , I surely must understand the concepts first?

 

I can not understand where you get Fn from, why and how the ground pushes back, why would the orbit be an ellipse etc.

 

You cannot understand orbital mechanics till you have got a grounding in the most basic physics. You have been told where the normal force arises from on numerous occasions and you have said it doesn't match your logic or intuition and moved on. NOTHING works if you take that course.

 

Re-read a basic text on the three laws.

 

 

I really want to understand, I do not want to see it another way, I want to see it how science see's it, but it is not my thought it does not tie into my logic and work.

 

I can not see the logic in it.

 

Why should your logic matter at all. SCIENCE WORKS! It is your fault if your logic disagrees with nature - it means either your axiomata are incorrect or you are misapplying them. Nature has no reason to comply with your predispositions or guesswork.

 

 

I thought the asteroid belt was a simple model, and passable has a model.

 

+energy = velocity, or minus energy = velocity.

 

Thermodynamics of their equilibrium orbit.

 

Is that not why the asteroids fly off?

 

This is arrant nonsense - and if you think this is a model go back and read this thread again. Don't just add words together in a sentence. Asteroids do NOT just fly off - they are mostly in a belt near mars in orbit; and we can predict their paths.

 

And what do you mean -''rejection of Newtonian gravity, and a cavalier disdain for some great Experiments does not bode well.''

 

I have not rejected them,

 

You rejected the observations of the Cavendish Experiment, and you claim that things just fall, that there is no normal, and that two house bricks are not attracted to each other ...

 

I am asking why is not this way or that way, trying to understand where my logic is flawed and where you are correct.

 

I can easily go on wiki and get the exact current models and copy them , but I like to learn myself and consider things first for myself before I rediscover current.

 

Please do not close this thread, all forums do it, you can see I am not a troll and genuine trying to learn, although yes I agree I have a wicked imagination.

 

Do you want to know what I have learn about models?

 

 

I know a lot now, and understand what an actual model is, this forum has learnt me.

 

You cannot intuit this stuff for yourself -- Newton (for crying out loud Newton) said "If I have seen further it is by standing on the shoulders of giants" - yet you wish to guess. You have learnt nothing about models as demonstrated by your latest attempt of an equation which puts velocity and energy as equivalents.

[Relative]

Does air and gases not have weight?

 

You cannot understand orbital mechanics till you have got a grounding in the most basic physics. You have been told where the normal force arises from on numerous occasions and you have said it doesn't match your logic or intuition and moved on. NOTHING works if you take that course.

 

Re-read a basic text on the three laws.

 

 

 

Why should your logic matter at all. SCIENCE WORKS! It is your fault if your logic disagrees with nature - it means either your axiomata are incorrect or you are misapplying them. Nature has no reason to comply with your predispositions or guesswork.

 

 

 

This is arrant nonsense - and if you think this is a model go back and read this thread again. Don't just add words together in a sentence. Asteroids do NOT just fly off - they are mostly in a belt near mars in orbit; and we can predict their paths.

 

 

You rejected the observations of the Cavendish Experiment, and you claim that things just fall, that there is no normal, and that two house bricks are not attracted to each other ...

 

 

You cannot intuit this stuff for yourself -- Newton (for crying out loud Newton) said If I have seen further it is from standing on the shoulders of giants - yet you wish to guess. You have learnt nothing about models as demonstrated by your latest attempt of an equation which puts velocity and energy as equivalents.

I have never said science did not work, and I stated time ago, that everything I state is just questions.

 

I reject experiments if all the variables have not been accounted for.

 

''said If I have seen further it is from standing on the shoulders of giants ''

 

And I stand on the giants shoulders.

 

I am only looking deep into what they say, and probably deeper.

 

And i do not know how you can say that my asteroid model is not a viable model.

 

 

The asteroid in a stable orbit does not leave the belt on its own accord, something must change to make it leave.

 

Thermodynamics means radiation as well, the asteroids gain radioactive energy, do they not?

[imatfaal]

I understand what science says , the normal , I understand where you get Fn from, but can not agree it is there, if all the forces add up to zero, then would we not float about, would we not feel our own body mass when we stand?

 

 

If I get past this Fn then maybe I will see it your way,

 

Let me clarify what you are saying, you are saying that the ground pushes back with a force equal to the weight opposing a force onto it?

 

 

To create a force F=ma , the ground is accelerating inwards, has no spring like properties, and no acceleration in the opposite direction.

 

 

To me all the force is inwards, and the ground compresses, uniaxial isotropic,

 

A question, if the ground pushes back, why is it that if I make a dent in soil using a hammer, the hole does not fill back up, if there is an opposing force f=ma from the ground, why does the ground not spring back into place?

And in the simple model of a block sliding down a hill, we have friction tag, Fn tag and gravity tag, why is there no air pressure/weight tag?

 

"To create a force F=ma , the ground is accelerating inwards" - where do you get this from. Gravity acts towards the centre of mass - the normal act perpendicular to the surface - there is no acceleration because most of the time these are equal and opposite. The ground does not need to be moving to exert a force - it opposes the force of gravity by the normal force.

 

"uniaxial isotropic" stop with the silly word salad.

 

"A question, if the ground pushes back" - the hammer stops - it decelerates, what force (FORCE do not mention anything else) causes it to decelerate?

 

 

"And in the simple model of a block sliding down a hill, we have friction tag, Fn tag and gravity tag, why is there no air pressure/weight tag?" Gravity and weight are same concept Air pressure - this is why we model, in this model we don't care; we don't think it will make a difference.

 

Get to the end of the simplest model in physics and then you can start to make it more complicated

[Fuzzwood]

Oh air most certainly has a mass. Why do you think a balloon falls toward the ground?

 

Answer: the balloon has a certain overpressure (you felt this one if you ever blew up a balloon). Due to this pressure, the air molecules are compressed a little towards eachother, resulting in the density of the air inside the balloon to exceed the density of the air around it. The air inside the balloon is thus a bit heavier than the air around it and thus the balloon falls at your feet.