Tesla vs Einstein

exchemist said:
Hang on he's right, surely, if the ball is compressible, which, in the scenario he describes, it is.
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Ok. That's why I wrote "provided your ball doesn't collapse under the water pressure". By "collapse" I meant to include "compress", but didn't state that clearly.

A reversed example of this kind of thing is air bubbles rising in water. They start of small and rise slowly, but as they go up the water pressure decreases and the bubbles expand. As they expand, the buoyant force increases and they rise more rapidly. I don't know if you notice that kind of thing when you're diving.
 
James R said:
Ok. That's why I wrote "provided your ball doesn't collapse under the water pressure". By "collapse" I meant to include "compress", but didn't state that clearly.

A reversed example of this kind of thing is air bubbles rising in water. They start of small and rise slowly, but as they go up the water pressure decreases and the bubbles expand. As they expand, the buoyant force increases and they rise more rapidly. I don't know if you notice that kind of thing when you're diving.
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Yes, people have to let air out of their jackets to control their ascent. And if you bring up a deep sea fish to the surface it often dies due to the swim baller expanding and rupturing.
 
James R said:
No.

Bouyancy was described brilliantly by Archimedes 2000 years ago. It turns out that the upward buoyant force on any object in water depends only on how much water it displaces. It doesn't depend on depth.

So, provided your ball doesn't collapse under the water pressure, it will have the same upward buoyant force on it regardless of whether it is 1 metre below the surface or at the bottom of the Pacific Ocean.

Of course, a beach ball won't work for that experiment, because it couldn't withstand the pressure. An appropriately designed submarine will do the job nicely, though.
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It's still a puzzle to me

OK the ball shrinks the deeper it under a force which is pushing it down

At some point it must loose boyantcy when it's mass becomes more dense than the water it displaces

A sub makes itself more dense by filling hollow tanks and sinking

It can hasten the sinking under propulsion to push itself down but even without propulsion it would sink

To rise it and return to boyantcy it must fill its flooded tank using compressed air and become overall less dense than the water it diplaces

However depth matters because as you go deeper the water itself becomes more dense

If you do not have sufficient air under sufficient pressure to drive out the denser water you are going to stay on the bottom of the ocean sorry

origin said:
You can work it out yourself with this handy-dandy site!

Oh, yeah you will need this too. The bulk density should be > 1 g/cc.
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I tried this but failed (miserably?)

Anyway thanks for the info but beyond my two neurones capabilities :)

:)
 
James R said:
Why is gravity always attractive and never repulsive?
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Considering quarks interaction between two mass; may be the resultant effect is always attractive.

James R said:
If we have a collection of electrons, all have negative charge, but apparently positive mass. Why?
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Electrons have negative charge equal to protons charge by magnitude. Comparatively electrons mass is negligible to protons mass. Though electrons have a positive mass. Presently electrons are mysterious. It is still unknown about their constituents.

James R said:
Explain how a generator or a motor relies on gravity.
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Compare Lorentz Force ( http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/magfor.html ) with Gravitational Force(Newtonian Model). By nature they are same. Both follows F=ma principle where F is force, m is mass and a is acceleration. So gravitational force(Newtonian Model) can have electromagnetic component within it.
 
hansda said:
Considering quarks interaction between two mass; may be the resultant effect is always attractive.
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But why always attractive regardless of electrical charge? If charge is supposed to cause gravity, that is.

Electrons have negative charge equal to protons charge by magnitude. Comparatively electrons mass is negligible to protons mass.
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Depends what you call negligible. Is 1/1836 negligible?

Presently electrons are mysterious. It is still unknown about their constituents.
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Electrons aren't made of any smaller particles, so far as we know at present.

Compare Lorentz Force ( http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/magfor.html ) with Gravitational Force(Newtonian Model). By nature they are same. Both follows F=ma principle where F is force, m is mass and a is acceleration. So gravitational force(Newtonian Model) can have electromagnetic component within it.
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F=ma is tied up with the definition of force, so all forces follow that.

The mathematical form of Coulomb's law is the same as Newton's law of gravity, but that is a result of the point-like nature of the sources of the fields, combined with their infinite range. And the point is that in Coulomb's law the charges can be negative, whereas in Newton's law the gravitational "charge" is always positive. So, the problem of why gravity is always attractive if it is a charge phenomenon remains unresolved.
 
Michael 345 said:
I tried this but failed (miserably?)
Anyway thanks for the info but beyond my two neurones capabilities :)
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It is probably easier to work backwards. Note - if you use rubber it will never reach neutral buoyancy - rubber is < 1 g/cc
using nylon with a density of 1.15 g/cc.
Assume the ball is composed of 1 cc of nylon.
how much air (assume air has no weight) volume must be added to the nylon to make it neutral.
So the weight of the nylon is 1.15 g
1.15g / 1.15cc = 1 g/cc or neutral buoyancy.
so the air must be compressed to a volume of 0.15 cc.
using the formula at the site start with whatever initial volume you want at 1 atmosphere and see what the final atm is
1 atm = (about)10 m of depth.
 
James R said:
And the point is that in Coulomb's law the charges can be negative, whereas in Newton's law the gravitational "charge" is always positive. So, the problem of why gravity is always attractive if it is a charge phenomenon remains unresolved.
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The electrical charges are not static. They are also intrinsically spinning. So, there is also a magnetic field surrounding these electrically charged particles. So, in the resultant effect, this magnetic field also should be considered.
 
I don't think Robert Arnett Otey has anything original. It seems to be a rehash of Walter Bowman Russell's Electric Universe.

I stopped reading that when it had centers of potential are drawn to centers of potential. I decided further reading would not be fruitful.

Its not the road to quantum gravity.
 
birch said:
He says it is anwered by buoyance and density and the argument is that the ball would sink if it were gravity.
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That doesn't make the slightest bit of sense. In a weightless enviroment the ball would not sink or float, gravity is required for buoyancy. So like I said he does not understand buoyancy, nor gravity it seems....
 
origin said:
That doesn't make the slightest bit of sense. In a weightless enviroment the ball would not sink or float, gravity is required for buoyancy. So like I said he does not understand buoyancy, nor gravity it seems....
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Either he is saying buoyancy does not make sense with gravity or that gravity is not related to weight as he makes a distinction that gravity is not needed to explain the process at all.
 
birch said:
Either he is saying buoyancy does not make sense with gravity or that gravity is not related to weight as he makes a distinction that gravity is not needed to explain the process at all.
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He is simply wrong.
Get a helium balloon and put it in a car. Now you can accelerate the car, you will be pushed back in your seat, a ping pong ball on the dashboard will be roll towards the back of the car and a cup of coffee on your seat will spill towards the back of the car. This is all pretty obvious right. It is because the acceleration of the car produces a force. Guess what, the helium balloons will move to the front of the car when you accelerate. Why? Because of the buoyancy of the balloons in the air. The acceleration of the car causes the air to move to the back of the car and therefore the pressure is higher in the back of the car. This is directly analogous to buoyancy in the water. The force from the car accelerating increases the air pressure in the back of the car and the force from gravity is causing the water pressure to be higher the deeper you go into the water.
This is fundamental physics, the guy on the site does not have a clue what he is talking about.
 
billvon said:
Well, neutrons are made of two down quarks (-1/3) and one up quark (+2/3) so the net charge is zero - but you could consider a neutron "made of charged particles."

But at a higher level the claim is silly. Claiming that gravity is mediated by charge (because things that are charged interact with gravity) is like claiming that horses run on electrical charge, because they eat grass and grass is made of charged particles.
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Is there any difference between Lorentz Force and Gravitational Force in Newtonian Model?
 
hansda said:
Is there any difference between Lorentz Force and Gravitational Force in Newtonian Model?
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First the Lorentz force was not found until after Newton died and secondly they are completely different.
 
hansda said:
What is the difference between these two forces,
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One electro-magnetic and the other is gravitational.
when they are applied on a mass m?
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A mass with a neutral charge will not feel a force from an electric field but it will feel a force from a gravitational field.
A charged mass will feel a force in an electric field as well as a force from the gravitational field. The force from an electrical field is much stronger than gravity.
 
hansda said:
If we consider gravity as a mechanical force(F=ma), then this force is related with electromagnetism as is evident in Generators and Motors.
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But if you consider that you are talking only about electromagnetism then...... Are electric field and magnetic field same /no difference between them ?
 
hansda said:
Is there any difference between Lorentz Force and Gravitational Force in Newtonian Model?
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Yes. For example, suppose a particle has mass $$m$$ and electric charge $$q$$. Then the force on it due to gravity $$g$$ will be $$mg$$ and the force due to an applied electric field $$E$$ will be $$Eq$$. The acceleration of the particle will then, assuming the electric and gravitational fields are the in the same direction, which they often are not:

$$a = g + \frac{Eq}{m}$$

It is experimentally observed that we can alter $$q$$ and $$m$$ completely independently and therefore observe different accelerations under different conditions. On the other hand, if it were really the case that gravity is a form of electromagnetism, then presumably we'd have $$m=q$$ and the acceleration would always be the same.
 
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