Denspressure vs Reality

Quote from: defender_of_truth on November 25, 2017, 03:39:02 AM

Regarding inertia, it's existence easily demonstrated by sitting in a spin chair. Sit down and put your arms out wide, give it a good kick to spin it, keep your legs in tight, then pull your arms straight in. If you find a good spinning chair, you will spin faster! No external force applied.

It's no different to cutting down the blades on a helicopter.
At first you have more resistance with longer blades whilst also using more energy.
If those blades could be snipped at that point you lessen the resistance but not the applied energy to overcome it, so now you have that applied energy overcoming the much less resistance of the helicopter blades, which would in crease the rpm.

It's just energy applied against atmospheric resistance.

Dont complicate the issue, go sit in a chair. A helicopter has a motor and is using fuel. You can't explain spinning faster in a chair by pulling in your arms without inertia of some sort. No power applied!

Quote from: Nightsky on November 25, 2017, 01:13:33 AM

In an effort to reach some conclusion, why not pick a simple situation that suits both parties and each performs a calculation to support their views along with an explanation. What the point of the argument is has become a bit lost.

When I was at school many years ago we did simple experiments using trollies on an inclined plane attached to a ticker tape. We simple measure space between the dots to determine the velocity and hence acceleration or deceleration.

The laws of motion are something that are well understood so to refute them would be quite some undertaking. Newton’s 3 laws of motion have been taught in every elementary physics class since physics classes were introduced. If someone is claiming to have found a problem with one or all of them, then please explain which of these laws are in error.

It's how the laws are applied and told which is the key to why we are duped.


Let's look at them.

First law: An object either remains at rest or continues to move at a constant velocity, unless acted upon by a force.

The law in itself is meaningless in one aspect whilst pretending to be something in another.
In reality none of it works.
An object cannot ever be at rest because there is always forces acting upon it and it, them. It's called atmosphere.
An object can never remain in motion at a constant velocity unless a force is constantly applied to it, so the claim that it's UNLESS a force is acting upon it, is a pointless waste.


However, if we go into fiction territory, this is when Newtons supposed law works, because people are now forced to confront the space ruse and the vacuum ruse that supposedly allows an object to be at rest or move in a frictionless void of nothingness, which brings us to another major issue.
If that's the case then there cannot ever be a force applied in the first place for anything to resist a motion or to change a motion.

The law is a nonsense.


Second law: Second law: Force on an object is equal to the mass  of that object multiplied by the acceleration of the object: F = ma.

So basically you apply energy to a dense mass and accelerate that mass or move that mass.
In simple terms what you put in as energy you get out as equal energy. Nothing more and nothing less.
Simple enough as long as it's used in the reality of the physical world we actually live in.


Third law: For every action there is an equal and opposite reaction.
In reality it's no different than the second law in terms of what it means.

Basically you only get out what you put in, in equal terms.
Your action creates and equal and opposite reaction to that action.
Whatever energy you apply you reap the reaction of that applied energy equally.
This works fine and likewise to the second law in a real Earth environment.

Fictional space and rockets and such use these laws in the wrong way and in a deliberately duping way with the pretence of equal and opposite reaction to action without the use of atmospheric pressure.
It's clear nonsense and that's why these laws get abused.

Your First Law isn’t right. It only works within a constant reference frame. For example, when you accelerate a car, loose objects move backwards relative to the car. To an outside observer, however, the loose things in the car would seem to stay still while the car moves away. When you drive around a left turn, loose objects will continue going forward, but relative to the car they will seem to go to the right. Finally, when you stop, loose objects will keep going. All of these things shift around in your car until they run into a part of the car that’s firmly connected to the motor/wheels/brakes supplying the force. While the car is cruising in a straight line at a steady speed, passengers and objects feel no forces (other than gravity), so it takes very little effort to toss a ball from the back seat to the front.

Your explanation of the Third Law is also wrong. Jet engines, for example, work by expelling compressed gas. By ejecting the gas, the engines create a reaction force that pushes back on the inside of the engine.

In one sense, you are right. The Second Law can be used with the Third, because the mass x the acceleration of the compressed gas going backward would be equal to the mass x the acceleration of the jet aircraft going forward.

Quote from: Jonny B Smart on November 24, 2017, 08:14:32 PM

A car on a hill will slow due to friction plus gravity depending on the angle of the hill. Gravity will slow a car by 4.9 m/s/s on a 45-degree-angled hill.

Slight correction, try 30°. Sorry.

Oh, right! Thanks...I’m a little rusty.

First law: An object either remains at rest or continues to move at a constant velocity, unless acted upon by a force.
The law in itself is meaningless in one aspect whilst pretending to be something in another.

How so?
It is quite simple: Objects don't just start moving for no reason. There is a force which makes them move.
Secondly, if they are moving, they need a force to stop them.

None of that is meaningless, nor is it pretending.

In reality none of it works.

No, in reality, this is what always happens.

An object cannot ever be at rest because there is always forces acting upon it and it, them. It's called atmosphere.

Would you prefer it if it said a net force?
What about if iti isn't in the atmosphere?

An object can never remain in motion at a constant velocity unless a force is constantly applied to it, so the claim that it's UNLESS a force is acting upon it, is a pointless waste.

All the evidence shows the opposite, that in fact you need to apply a force to stop it.

If that's the case then there cannot ever be a force applied in the first place for anything to resist a motion or to change a motion.

Why?

The law is a nonsense.

Nope, just your analysis of it.

Second law: Second law: Force on an object is equal to the mass  of that object multiplied by the acceleration of the object: F = ma.
So basically you apply energy to a dense mass and accelerate that mass or move that mass.

Not energy, FORCE!!
There is a slight difference.

Third law: For every action there is an equal and opposite reaction.
In reality it's no different than the second law in terms of what it means.

Debatable, but somewhat.

Basically you only get out what you put in, in equal terms.
Your action creates and equal and opposite reaction to that action.
Whatever energy you apply you reap the reaction of that applied energy equally.
This works fine and likewise to the second law in a real Earth environment.

Nope. Completely wrong.
To express it in terms of energy:
You apply energy E to an object, this is an action, expressed as dE=E.
This has an equal and opposite term dE=-E which applies to you.
If you apply energy to accelerate an object then this energy comes from you.
Or to express it in terms of force:
If you apply force to an object to accelerate it, then the object applies a force to you that is equal in magnitude but opposite in direction.

Fictional space and rockets and such use these laws in the wrong way

No. Real rockets use these laws in the correct way.

with the pretence of equal and opposite reaction to action without the use of atmospheric pressure.

You don't need atmospheric pressure.
By the very nature of the law, if you throw an object away by applying a force to it, an equal and opposite force exists on you.

Springboard.

A load of nonsense you are yet to explain or justify.

Deceleration.

Yes, that is what happens.
That is what you need to explain.

It's no different to cutting down the blades on a helicopter.

Somewhat, they are both related to moment of inertia.
But you are describing spinning them up, not what happens.
If you had a large blade spinning, and then cut it, it would keep spinning at the same rate with the outer bits flying off.

At first you have more resistance with longer blades whilst also using more energy.

Yes, the larger blades have a larger moment of inertia.

If those blades could be snipped at that point you lessen the resistance but not the applied energy to overcome it

This is not what we are discussing. No additional energy is being applied.

Quote from: Nightsky on November 25, 2017, 01:13:33 AM

In an effort to reach some conclusion, why not pick a simple situation that suits both parties and each performs a calculation to support their views along with an explanation.

He doesn't due numbers.
He will only provide qualitative analysis in complete isolation.

This is so he can avoid admitting his nonsense is nonsense.

Quote from: Nightsky on November 25, 2017, 01:13:33 AM

The laws of motion are something that are well understood so to refute them would be quite some undertaking. Newton’s 3 laws of motion have been taught in every elementary physics class since physics classes were introduced. If someone is claiming to have found a problem with one or all of them, then please explain which of these laws are in error.

This particular discussion is regarding the first law.
He is claiming inertia does not exist, that if a car was going up a hill at constant speed and you cut power it would stop instantly.

The claims similar to the third law is him just spouting nonsense as if it should mean something.

He Sceptimatic, has obviously never driven a car. Anyone who has can testify, take your foot of the accelerator pedal and the car will eventually slow down and come to a halt. The distance the car travels due to its inertia is dependent on road and weather conditions plus the inherent friction losses, rolling resistance etc possessed by the car. Surely this is beyond debate as it’s so easily testable.

Quote from: sceptimatic on November 25, 2017, 03:48:15 AM

Quote from: defender_of_truth on November 25, 2017, 03:39:02 AM

Regarding inertia, it's existence easily demonstrated by sitting in a spin chair. Sit down and put your arms out wide, give it a good kick to spin it, keep your legs in tight, then pull your arms straight in. If you find a good spinning chair, you will spin faster! No external force applied.

It's no different to cutting down the blades on a helicopter.
At first you have more resistance with longer blades whilst also using more energy.
If those blades could be snipped at that point you lessen the resistance but not the applied energy to overcome it, so now you have that applied energy overcoming the much less resistance of the helicopter blades, which would in crease the rpm.

It's just energy applied against atmospheric resistance.

Dont complicate the issue, go sit in a chair. A helicopter has a motor and is using fuel. You can't explain spinning faster in a chair by pulling in your arms without inertia of some sort. No power applied!

There is no complication.
A helicopter has a motor and fuel just as the person replicates by energy and mass against resistance.
The principles are exactly the same.
Arms pulling into a chair from outstretched are the same principle as the helicopter.

There is no complication.

Yes there is. A pretty big one.

A helicopter has a motor and fuel just as the person replicates by energy and mass against resistance.

The person releases that energy once, and continues to swing. The helicopter in your example continually uses energy.
As such, the principles are different.
To make it worse you also go from changing distribution of mass to changing the mass itself.

He Sceptimatic, has obviously never driven a car. Anyone who has can testify, take your foot of the accelerator pedal and the car will eventually slow down and come to a halt. The distance the car travels due to its inertia is dependent on road and weather conditions plus the inherent friction losses, rolling resistance etc possessed by the car. Surely this is beyond debate as it’s so easily testable.

It's very easily testable.
A nice extremely steep hill on a dry day with a good road grip and a car that is capable of climbing the hill.
Start at the bottom and build up speed.
Let me know when you have to gear down and then let me know at what stage you can keep a constant speed to get you up that hill.

As soon as you reach a constant speed depress the clutch pedal or turn off the ignition and see if you carry on moving forward.
You'll stop dead so try and ne be honest with yourself because you've got nothing to prove to me but plenty to prove to yourself if you class yourself as honest.

Quote from: sceptimatic on November 25, 2017, 04:35:42 AM

There is no complication.

Yes there is. A pretty big one.

Quote from: sceptimatic on November 25, 2017, 04:35:42 AM

A helicopter has a motor and fuel just as the person replicates by energy and mass against resistance.

The person releases that energy once, and continues to swing. The helicopter in your example continually uses energy.
As such, the principles are different.
To make it worse you also go from changing distribution of mass to changing the mass itself.

Chop the blades and cut the helicopter engine to neutral. Same scenario.

It's very easily testable.

That's right, and guess what every test shows? That the car keeps on going.

As soon as you reach a constant speed depress the clutch pedal or turn off the ignition and see if you carry on moving forward.

Is that your problem? You just cut the ignition and have the engine act as a brake?

You'll stop dead so try and ne be honest with yourself because you've got nothing to prove to me but plenty to prove to yourself if you class yourself as honest.

It has been done plenty of times, you never stop dead.
We have proven it to ourselves.
You are the one with a lot to prove.

Chop the blades and cut the helicopter engine to neutral. Same scenario.

No. Completely different.

Quote from: sceptimatic on November 25, 2017, 04:46:45 AM

As soon as you reach a constant speed depress the clutch pedal or turn off the ignition and see if you carry on moving forward.

Is that your problem? You just cut the ignition and have the engine act as a brake?

In bold. Try it.

Quote from: sceptimatic on November 25, 2017, 04:48:03 AM

Chop the blades and cut the helicopter engine to neutral. Same scenario.

No. Completely different.

Same scenario.

I am trying to think of a sport that doesn’t rely on momentum. Tennis players don’t push the ball over the net. Soccer players don’t run around with the ball stuck to their foot.

I am trying to think of a sport that doesn’t rely on momentum. Tennis players don’t push the ball over the net. Soccer players don’t run around with the ball stuck to their foot.

What you need to be looking at is vertical momentum at a constant velocity.

What are the things that can achieve that?

Quote from: Jonny B Smart on November 25, 2017, 05:18:07 AM

I am trying to think of a sport that doesn’t rely on momentum. Tennis players don’t push the ball over the net. Soccer players don’t run around with the ball stuck to their foot.

What you need to be looking at is vertical momentum at a constant velocity.

What are the things that can achieve that?

So does denpressure not act in a horizontal direction? That would be an important clarification.

Quote from: sceptimatic on November 25, 2017, 05:22:36 AM

Quote from: Jonny B Smart on November 25, 2017, 05:18:07 AM

I am trying to think of a sport that doesn’t rely on momentum. Tennis players don’t push the ball over the net. Soccer players don’t run around with the ball stuck to their foot.

What you need to be looking at is vertical momentum at a constant velocity.

What are the things that can achieve that?

So does denpressure not act in a horizontal direction? That would be an important clarification.

Yep but this topic has turned into the rocket topic as well and is getting skewed.

Quote from: Jonny B Smart on November 25, 2017, 05:18:07 AM

I am trying to think of a sport that doesn’t rely on momentum. Tennis players don’t push the ball over the net. Soccer players don’t run around with the ball stuck to their foot.

What you need to be looking at is vertical momentum at a constant velocity.

What are the things that can achieve that?

Yes, but the path of a baseball often includes a vertical component. After the ball leaves the bat, nothing but internal kinetic energy keeps it going up, up, up...homerun! Of course, there has to be a significant horizontal vector as well. It seems that you’re saying that fly balls should never happen. Basketball players should only be able to dunk, not lob the ball into the basket.

Here’s a simpler test yet. Try jumping. It is impossible for you to apply any force against the ground once your feet leave the floor. Can you get both feet off the floor? Yes? Case closed.

Quote from: sceptimatic on November 25, 2017, 05:22:36 AM

Quote from: Jonny B Smart on November 25, 2017, 05:18:07 AM

I am trying to think of a sport that doesn’t rely on momentum. Tennis players don’t push the ball over the net. Soccer players don’t run around with the ball stuck to their foot.

What you need to be looking at is vertical momentum at a constant velocity.

What are the things that can achieve that?

Yes, but the path of a baseball often includes a vertical component. After the ball leaves the bat, nothing but internal kinetic energy keeps it going up, up, up...homerun! Of course, there has to be a significant horizontal vector as well. It seems that you’re saying that fly balls should never happen. Basketball players should only be able to dunk, not lob the ball into the basket.

Here’s a simpler test yet. Try jumping. It is impossible for you to apply any force against the ground once your feet leave the floor. Can you get both feet off the floor? Yes? Case closed.

What exactly are you arguing against with this?

Quote from: Jonny B Smart on November 25, 2017, 05:42:31 AM

Quote from: sceptimatic on November 25, 2017, 05:22:36 AM

Quote from: Jonny B Smart on November 25, 2017, 05:18:07 AM

I am trying to think of a sport that doesn’t rely on momentum. Tennis players don’t push the ball over the net. Soccer players don’t run around with the ball stuck to their foot.

What you need to be looking at is vertical momentum at a constant velocity.

What are the things that can achieve that?

Yes, but the path of a baseball often includes a vertical component. After the ball leaves the bat, nothing but internal kinetic energy keeps it going up, up, up...homerun! Of course, there has to be a significant horizontal vector as well. It seems that you’re saying that fly balls should never happen. Basketball players should only be able to dunk, not lob the ball into the basket.

Here’s a simpler test yet. Try jumping. It is impossible for you to apply any force against the ground once your feet leave the floor. Can you get both feet off the floor? Yes? Case closed.

What exactly are you arguing against with this?

When you jump, you accelerate upward by pushing off the ground. You push down (f=ma), but you go up (due to the reaction force of the Third Law). Your legs provide the power, but they can only push if your feet are touching the floor. Once your legs are fully extended, the momentum that your legs have imparted to your body keep your body moving up until your feet are off the floor. No more pushing, but up you go like a little rocket. Of course, that’s a short ride, but flew you did.

When you jump, you accelerate upward by pushing off the ground. You push down (f=ma), but you go up (due to the reaction force of the Third Law). Your legs provide the power, but they can only push if your feet are touching the floor. Once your legs are fully extended, the momentum that your legs have imparted to your body keep your body moving up until your feet are off the floor. No more pushing, but up you go like a little rocket. Of course, that’s a short ride, but flew you did.

Yep. That's your acceleration springboard effect until your feet leave the deck and from then on you are decelerating into the sky.
What's the issue here?

Quote from: Jonny B Smart on November 25, 2017, 06:25:12 AM

When you jump, you accelerate upward by pushing off the ground. You push down (f=ma), but you go up (due to the reaction force of the Third Law). Your legs provide the power, but they can only push if your feet are touching the floor. Once your legs are fully extended, the momentum that your legs have imparted to your body keep your body moving up until your feet are off the floor. No more pushing, but up you go like a little rocket. Of course, that’s a short ride, but flew you did.

Yep. That's your acceleration springboard effect until your feet leave the deck and from then on you are decelerating into the sky.
What's the issue here?

It’s just like rockets and cars. You said that rockets and cars stop when the engine is cut, but they don’t, neither do balls, and neither do you.

Quote from: sceptimatic on November 25, 2017, 06:49:39 AM

Quote from: Jonny B Smart on November 25, 2017, 06:25:12 AM

When you jump, you accelerate upward by pushing off the ground. You push down (f=ma), but you go up (due to the reaction force of the Third Law). Your legs provide the power, but they can only push if your feet are touching the floor. Once your legs are fully extended, the momentum that your legs have imparted to your body keep your body moving up until your feet are off the floor. No more pushing, but up you go like a little rocket. Of course, that’s a short ride, but flew you did.

Yep. That's your acceleration springboard effect until your feet leave the deck and from then on you are decelerating into the sky.
What's the issue here?

It’s just like rockets and cars. You said that rockets and cars stop when the engine is cut, but they don’t, neither do balls, and neither do you.

Vertical and constant.

Quote from: Jonny B Smart on November 25, 2017, 07:03:25 AM

Quote from: sceptimatic on November 25, 2017, 06:49:39 AM

Quote from: Jonny B Smart on November 25, 2017, 06:25:12 AM

When you jump, you accelerate upward by pushing off the ground. You push down (f=ma), but you go up (due to the reaction force of the Third Law). Your legs provide the power, but they can only push if your feet are touching the floor. Once your legs are fully extended, the momentum that your legs have imparted to your body keep your body moving up until your feet are off the floor. No more pushing, but up you go like a little rocket. Of course, that’s a short ride, but flew you did.

Yep. That's your acceleration springboard effect until your feet leave the deck and from then on you are decelerating into the sky.
What's the issue here?

It’s just like rockets and cars. You said that rockets and cars stop when the engine is cut, but they don’t, neither do balls, and neither do you.

Vertical and constant.

Are you saying that rockets, balls, cars, and people have different laws of physics? Or are you saying that vertical physics is different than horizontal physics?

It doesn’t matter which direction you are moving. Moving at a constant velocity requires no force. force = mass x ACCELERATION, remember? No acceleration (change in velocity) means no force.

Moving against a force (gravity or air resistance, for example) requires a balanced force to maintain velocity.

Quote from: Nightsky on November 25, 2017, 04:33:35 AM

He Sceptimatic, has obviously never driven a car. Anyone who has can testify, take your foot of the accelerator pedal and the car will eventually slow down and come to a halt. The distance the car travels due to its inertia is dependent on road and weather conditions plus the inherent friction losses, rolling resistance etc possessed by the car. Surely this is beyond debate as it’s so easily testable.

It's very easily testable.
A nice extremely steep hill on a dry day with a good road grip and a car that is capable of climbing the hill.
Start at the bottom and build up speed.
Let me know when you have to gear down and then let me know at what stage you can keep a constant speed to get you up that hill.

As soon as you reach a constant speed depress the clutch pedal or turn off the ignition and see if you carry on moving forward.
You'll stop dead so try and ne be honest with yourself because you've got nothing to prove to me but plenty to prove to yourself if you class yourself as honest.

Except that isn't what happens.  You begin to slow down, you do not stop dead.  If you were moving at 100 kph and you instantly stopped you would likely be dead.
Your example does not match my real world experience.

Quote from: Nightsky on November 25, 2017, 04:33:35 AM

He Sceptimatic, has obviously never driven a car. Anyone who has can testify, take your foot of the accelerator pedal and the car will eventually slow down and come to a halt. The distance the car travels due to its inertia is dependent on road and weather conditions plus the inherent friction losses, rolling resistance etc possessed by the car. Surely this is beyond debate as it’s so easily testable.

It's very easily testable.
A nice extremely steep hill on a dry day with a good road grip and a car that is capable of climbing the hill.
Start at the bottom and build up speed.
Let me know when you have to gear down and then let me know at what stage you can keep a constant speed to get you up that hill.

As soon as you reach a constant speed depress the clutch pedal or turn off the ignition and see if you carry on moving forward.
You'll stop dead so try and ne be honest with yourself because you've got nothing to prove to me but plenty to prove to yourself if you class yourself as honest.

Do you perchance drive a car like Fred Flintstone?

Not trying to get involved in this debate, looks hectic enough as it is, just trying to understand the model.

If we took, say, a platform on some kind of mechanism that moved up at a constant, fast speed, and placed a ball on top of it, then that ball would be initially trapped on the surface of the platform keeping going up at a constant speed.
Would it be correct to say that if the platform was to quickly decelerate, stop dead or reverse, the ball in question would not leave the surface of the platform but would instead match speed with it at every second?
And if instead the platform was to accelerate up before slowing/stopping/reversing then and only then would the ball leave the surface of the platform and be thrown up?

And if this is accurate then, companion question to the first situation, how could you tell the difference between the ball keeping to the surface of the platform staying at a dead stop, and the ball decelerating at the same rate as the platform?

Assuming these questions are clear this'll probably be my only post on this topic, thanks in advance!

Constant fast speed....
I think some people here could do with taking a class in elementary physics.

Not trying to get involved in this debate, looks hectic enough as it is, just trying to understand the model.

If we took, say, a platform on some kind of mechanism that moved up at a constant, fast speed, and placed a ball on top of it, then that ball would be initially trapped on the surface of the platform keeping going up at a constant speed.
Would it be correct to say that if the platform was to quickly decelerate, stop dead or reverse, the ball in question would not leave the surface of the platform but would instead match speed with it at every second?
And if instead the platform was to accelerate up before slowing/stopping/reversing then and only then would the ball leave the surface of the platform and be thrown up?

And if this is accurate then, companion question to the first situation, how could you tell the difference between the ball keeping to the surface of the platform staying at a dead stop, and the ball decelerating at the same rate as the platform?

Assuming these questions are clear this'll probably be my only post on this topic, thanks in advance!

If all ball is sitting on a flat board is clamped in place until it got up to speed, and then the ball is released, it would roll off the back due to the force of wind resistance. If it is prevented from rolling back, and the board slows rather quickly, the ball will roll off the front due to its inertia. If a board with a ball on top accelerated upward and then stops, the ball would go flying up. Gravity would immediately start to decelerate it until it reverses direction and drops to the ground.

Quote from: Jonny B Smart on November 25, 2017, 07:03:25 AM

It’s just like rockets and cars. You said that rockets and cars stop when the engine is cut, but they don’t, neither do balls, and neither do you.

Vertical and constant.

What do you even mean?

Project any fairly dense object vertical at 10 m/s and it will take roughly one second to stop, in which time it will have travelled up roughly 5 m.
Then it will start to fall and be back to the original level in roughly one more second travelling down at close to 10 m/s.

Video it on your camera or phone  and check the motion frame by frame - and remember, I sad roughly.