126 replies to this topic

[Pliny]

[quote name='kimmy' date='27 October 2011 - 10:37 PM' timestamp='1319780228' post='723600']
If you lean a stick against a wall, the stick is applying force to the wall. Possibly for hours, days, or even many many years. Does that mean the stick is generating infinite energy?


No, Pliny, it does not. And as usual the problem here is that you just don't understand what you're talking about.
You're expending energy by pressing against the wall-- contracting your muscles uses chemical energy, and generates heat. But you're not generating energy any more than the stick leaning against the wall is generating energy.
[/quote]
Why would I think the stick is generating infinite energy in such case? The force of gravity is the only thing in play here keeping things in an equilibrium. Now if the stick were off the ground, just sort of up against the wall, seemingly defying gravity, I would wonder how that could be. If there were no mass holding it up on the wall there would have to be some force holding it up.

[quote]
And holding the ball at constant height is no different from a table holding a ball at constant height. Is the table burning energy? If a ball sits on a table for 100 years, does that mean that the table has generated an incalculable amount of energy during that time? No.
[/quote]
All you are doing in this instance is inserting a mass so energy does not need to be expended.

If I hold my arms out in front of me it takes energy for me to hold them there. If I put a table underneath them they are at rest and I no longer need to expend any energy holding them up.
[quote]
Nope.



yep



nope



yep
[/quote]
If you say so.
[quote]
If you put a brick between two magnets to keep them apart, is the brick generating energy? Nope.
[/quote]
Right. A mass is keeping them apart. The same as a table keeps things from falling on the floor. There is no energy necessary to hold them up in that case and in your case there is no energy necessary to keep the magnets apart.
[quote]
Your muscles are burning chemical energy while you're holding the magnets in place, but that energy isn't being added to the system of magnets. It's being lost as heat. It's not being added to the system of the magnets.
[/quote]

-k
[/quote]
So all my muscles are doing are burning chemical energy and producing heat? There is no work being done.
Really?

With one hand on each magnet, the magnets when brought into proximity to each other will pull my hands together. Is there any energy used to do that? Usually my muscles have to burn some chemicals and produce some heat to bring my hands together.

Edited by Pliny, 29 October 2011 - 07:30 AM.

[kimmy]

Why would I think the stick is generating infinite energy in such case? The force of gravity is the only thing in play here keeping things in an equilibrium. Now if the stick were off the ground, just sort of up against the wall, seemingly defying gravity, I would wonder how that could be. If there were no mass holding it up on the wall there would have to be some force holding it up.

A mass is not holding the stick up. The normal force exerted by the ground on the stick is holding it up.

It's not mass that opposes the force of gravity. It's another force. If an object is stationary, it's because all the forces acting on that object balance.

In the case of a stick leaning against the wall, it is normal force balancing gravity.

In the case of a magnet on a fridge, the force opposing gravity is static friction.

All you are doing in this instance is inserting a mass so energy does not need to be expended.

I'm inserting something that applies normal force.

As far as the ball is concerned, there's no difference whether it's being held up by a table or by your hand, so why would you think energy is being generated in one scenario but not the other?

The only difference between the table and your hand is that your hand will only provide normal force to hold the ball up until your muscles run out of chemical energy.

If you say so.

I do. You can take my word for it, or you can study why for yourself. I can't be bothered to explain concepts that are covered in basic high school physics.

Right. A mass is keeping them apart. The same as a table keeps things from falling on the floor. There is no energy necessary to hold them up in that case and in your case there is no energy necessary to keep the magnets apart.

yep

So all my muscles are doing are burning chemical energy and producing heat? There is no work being done.
Really?

yep

With one hand on each magnet, the magnets when brought into proximity to each other will pull my hands together. Is there any energy used to do that? Usually my muscles have to burn some chemicals and produce some heat to bring my hands together.

When the magnets are in static position, they have zero kinetic energy and they have potential energy defined as (their distance from each other) times (attractive force between them).

Let go of the magnets, and the potential energy converts to kinetic energy. They get closer together so they have less potential energy but they are moving faster so they have more kinetic energy. At the moment they crash together, they have zero potential energy and the kinetic energy at the moment of impact is equal to the potential energy they had when you were holding them apart. After the moment of impact, the potential energy is zero, the kinetic energy is zero, and all of that energy has been converted to sound and vibration and heat.

If you're still holding on to the magnets but relax your arms so that the magnets are slowed, then it's the same except that some of the potential energy of the magnets is not converted to kinetic energy and is instead absorb by the muscles in your arms-- lost as heat-- and the collision between the magnets has less energy.

So now how is what you just said different from what I have been saying? That should be easy to figure out.

I'm having a really hard time figuring out what you're saying, except that as far as I can tell you think that since both observers see the speed of light to be the same, you can conclude that both observers must be stationary relative to each other. Which indicates that you've completely missed the point.



-k

Edited by kimmy, 29 October 2011 - 12:19 PM.

[Pliny]

A mass is not holding the stick up. The normal force exerted by the ground on the stick is holding it up.
It's not mass that opposes the force of gravity. It's another force. If an object is stationary, it's because all the forces acting on that object balance.

A state of gravitational equilbrium is always trying to be maintained.

In the case of a stick leaning against the wall, it is normal force balancing gravity.

Yes. If the stick were off the ground, as I said, without visible means of support, then it would be out of equilibrium, a state that is not possible.

In the case of a magnet on a fridge, the force opposing gravity is static friction.

Static friction as a description of a magnet opposing gravity is easily dismissed when you consider a magnet will hang from a horizontal ferrous material.

As far as the ball is concerned, there's no difference whether it's being held up by a table or by your hand, so why would you think energy is being generated in one scenario but not the other?

The only difference between the table and your hand is that your hand will only provide normal force to hold the ball up until your muscles run out of chemical energy.

My muscles, in holding the ball up, are expending energy then which will eventually deplete. Right?

I generate the energy to hold it up. That's why I think energy is being generated in one scenario but not the other. Although nothing is moving when I am holding the ball up out of gravitational equilibrium, energy is still being expended to do so and you seem to agree.

I'm having a really hard time figuring out what you're saying, except that as far as I can tell you think that since both observers see the speed of light to be the same, you can conclude that both observers must be stationary relative to each other. Which indicates that you've completely missed the point.



-k

I think if you look, I never said that the observers are stationary relative to each other. I said that they are each stationary relative to the speed of light which I don't believe is any different than what you are saying or what special relativity suggests.

Gotta go.

Edited by Pliny, 31 October 2011 - 09:34 AM.

[kimmy]

A state of gravitational equilbrium is always trying to be maintained.

I'm not sure what you're trying to say, but whatever it is, the way you're saying it isn't accurate.

Yes. If the stick were off the ground, as I said, without visible means of support, then it would be out of equilibrium, a state that is not possible.

States where things are not in equilibrium are entirely possible. Any situation where something is accelerating is an example. F=ma ... if it were impossible for a system to be out of equilibrium, then F would always equal zero and nothing would ever accelerate.

I think the idea you're floundering around looking for is this: a system will act to minimize potential energy and maximize kinetic energy. (that statement is my own "original research." I think it's essentially a restatement of the 2nd law of thermodynamics in a way that's easier for Kimmy to keep a handle on it.)

Static friction as a description of a magnet opposing gravity is easily dismissed when you consider a magnet will hang from a horizontal ferrous material.

Your grasp of the concepts we're discussing is easily dismissed when you consider the colossal stupidity of that statement.

Of course when you rotate the system 90 degrees the forces acting on the magnet are different.

If the magnet is hanging from the ceiling instead of from your fridge door, the magnetic force and gravity are in equilibrium and there's still no work being done.

My muscles, in holding the ball up, are expending energy then which will eventually deplete. Right?

I generate the energy to hold it up. That's why I think energy is being generated in one scenario but not the other. Although nothing is moving when I am holding the ball up out of gravitational equilibrium, energy is still being expended to do so and you seem to agree.

Ok, so you understand that your table is not expending energy to hold a mass against gravity, so you apparently at least understand that holding a mass stationary against the force of gravity does not, in itself generate energy.

And you understand that your arm muscles have to spend energy to remain rigid while the table does not.

So I guess the missing piece of the puzzle for you is comprehending that a magnet is like a table, not like your arm. Let me help you with that. The magnet is like the table, not like your arm.

The table does not spend any energy to generate the Normal Force that is opposing gravity. The magnet hanging from the ceiling does not spend any energy to generate normal force. Your muscles need to spend energy to remain contracted.



So with that out of the way, let's get back to the point. You said you had all these problems because there were "anomalies" like infinite sources of energy. But it turns out that what you think is an infinite source of energy is actually just another example of your inept grasp of the subject matter.

Has it occurred to you that maybe you're just not the right guy to revolutionize modern physics?

I think if you look, I never said that the observers are stationary relative to each other. I said that they are each stationary relative to the speed of light which I don't believe is any different than what you are saying or what special relativity suggests.

So where do we get to the "anomaly" you wanted to talk about?

I can't even accuse you of trying to move the goalposts... you can't even find the goalposts anymore.


-k

[Pliny]

I'm not sure what you're trying to say

This is true.

[kimmy]

This is true.

Well... in your mind perhaps all of this is a result of my inability to comprehend the words coming out of your mouth. But in truth, all of this is a result of your inability to comprehend what you're even talking about.

Maybe take some evening courses so you can learn high-school physics. Or maybe just stick to whining about taxes.

-k

[naturally]

Was it Copernicus who said, when asked about the role of god in his theory of planetary motion, I have no need for a god to play any part in this!
It is still the case today! Always will be!