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imagegeek
I suppose that your understanding of the pipe concept would render a gyroscope used in space in operable as it is inside the space ship , the space ship is a closed system pertaining to the gyroscope.

but thankfully they do use gyroscopes in space ships in space.

the internal gyroscopes do not place a force on the outside of the space ship , it places a force on the inside of the ship.

the gyroscopes keep the ships orentation in a certain position relative to the earth.

otherwise the iss could not maintain its orentation


thus fouling up your entire concept of the laws of newton.
and kallogs entire argument is hereby null.

and heres proof.

the iss and its gyroscopes are used to maintain orentation

meaning that the internal forces are turning the iss !!!

I win unless you can prove otherwise.

remember your entire argument is based on newtons laws as you understand them , so if the pipe cannot move without an external force applied to it , then the iss also cannot move without an external force applied to it.

and if the gyroscope was not turning then the ship would turn therefore the gyroscope is applying a force from inside the ship to keep the iss from turning.

pretty simple stuff.




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You can easily substitute the symbols for numbers, please do. I chose not to because I find it easier that way.

Now I've shown no long-term movement with 2 masses, you can expand the calculation for 20 masses. But why 20? Why not 10? 100? 2?

Quote:

now when 1 reaches the end the most it can subtract is
25 kg.


This might be the crucial mistake.
If a mass has:
25kg and 1m/s. Momentum = 25kgm/s
Then it turns around in a u-bend, it ends up with
25kg and -1m/s. Momentum = -25kgm/s

The momentum has reduced by 50kgm/s!!!! Not 25.



Quote:

I never said the ends were brakes their just turnarounds.


Yep. If an object just turns around, then its moment becomes the negative of what it was before. Bounce a ball against a wall, and it's direction changes to negative, but its speed remains roughly the same. It's lost TWICE the momentum it had.

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He's saying the center of mass won't move. Which is what he said. The pipe can still move, just not the center of mass of it and its contents.


Originally Posted By: paul
Quote:
The center of mass of the whole system - i.e. pipe + mass - will not move, as observed by an outside observer.


so your saying that if Im standing outside of the pipe I would not notice that it moves , because it will not move.

correct?

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Originally Posted By: paul

meaning that the internal forces are turning the iss !!!


Correct, but they are not changing the angular momentum of
the whole system (ISS + gyroscopes).

By analogy, moving masses in a pipe are not changing the linear momentum of the whole system (pipe + masses).

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Originally Posted By: paul
the internal gyroscopes do not place a force on the outside of the space ship , it places a force on the inside of the ship.

Yep.

Originally Posted By: paul
the gyroscopes keep the ships orentation in a certain position relative to the earth.

Yep.

Originally Posted By: paul

otherwise the iss could not maintain its orentation


Depends on your reference frame - without a gyroscope the ISS would keep its orientation relative to it own inertial frame, plus whatever changes in orientation were induced by the movement of people/supplies within the ISS itself.

Originally Posted By: paul

thus fouling up your entire concept of the laws of newton.
and kallogs entire argument is hereby null.

Nope, as I pointed out in my post the gyroscopes use newtons laws to maintain the orientation of spacecraft, but cannot be used to change the momentum of the spacecraft.

They disprove your idea; they clearly show that internal forces - i.e. the gyroscopes - are completely unable to alter the momentum of the ship in which they are contained. You can use the gyroscope to reorientate the ship, but you cannot use it to move the center of mass - i.e. fly the ISS to the moon.

Heck, if all you needed a gyroscope once in orbit, why would they have built the Saturn booster rockets to get to the moon? A far simpler way would have been a much smaller rocket + a gyroscope.

The answer is simple - and its not because NASA is dumb. Its because gyroscopes and other internal forces are unable to alter the momentum of an object.

Originally Posted By: paul
and heres proof.
the iss and its gyroscopes are used to maintain orentation

meaning that the internal forces are turning the iss !!!


And? We never once said changes in orientation were not possible - only that changes in momentum - as in what you need for a rocket engine - cannot occur.

Notice in your video the ISS is turning; it is not rocketing off to the moon. Orbit is the same, momentum is the same, its just pointing another way.

The real irony is the turning of the ISS is achieved by the very law you are trying to violate - conservation of momentum. Changes in the spinning of the gyroscope create a change in the angular momentum of that gyroscope. Since momentum is conserved in a closed system, the ISS itself must turn to maintain the systems total angular momentum.

Originally Posted By: paul
I win unless you can prove otherwise.

Win what, the prize for being the worst at grade 10 physics?

Originally Posted By: paul

remember your entire argument is based on newtons laws as you understand them , so if the pipe cannot move without an external force applied to it , then the iss also cannot move without an external force applied to it.

Re-writing our claims again, are we? Kellog and I have been clear since the first post that momentum cannot change. We've also been clear since the first day that shifts in the relative positions of components (i.e. the pipe verses your internal mass) can also occur.

In fact, if you had the vaguest idea of how momentum is determined, you'd realize that shifts in the positioning of the pipe verses the internal mass are necessary to maintain momentum when one object moves within another. If those shifts did not occur, the center of mass would move, and thus the momentum of the system would change.

But what cannot change is the momentum of the whole. A concept clearly demonstrated by your ISS video.

Originally Posted By: paul
and if the gyroscope was not turning then the ship would turn therefore the gyroscope is applying a force from inside the ship to keep the iss from turning.


Actually, you've got that backwards. Relative to its inertial frame, the iss will not spin. It only appears to spin because it orbits the earth. Thus the iss has to be given spin (1 rotation/orbit) so that it always faces the same direction relative to the earth. The gyroscope is used to maintain that spin. The gyroscope is also used to maintain position when mass is moved around inside - other wise, someone walking from one end to the other could alter the iss's orientation in space.

However, no matter what you do with that gyroscope, the ISS stays in the same orbit. The movement of that internal mass, and thus the force created by that internal mass, is completely unable to produce thrust.

Which is the polar opposite of your claim.

Bryan


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Originally Posted By: kallog

Correct, but they are not changing the angular momentum of
the whole system (ISS + gyroscopes).

By analogy, moving masses in a pipe are not changing the linear momentum of the whole system (pipe + masses).


The sad part is that I took ~200 lines to say the same thing frown

Bryan


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Quote:
This might be the crucial mistake.
If a mass has:
25kg and 1m/s. Momentum = 25kgm/s
Then it turns around in a u-bend, it ends up with
25kg and -1m/s. Momentum = -25kgm/s

The momentum has reduced by 50kgm/s!!!! Not 25.


No , absoloutly not.
I notice you are dreaming again kallog.

but after it leaves the turn round it isnt accelerating !!
its free floating , thus your -25kgm/s is null and void.

and it is the acceleration of the masses that causes pipe momentum.

we are not decelerating the masses yet , other than the slight deceleration as the masses pass through the turnarounds , sure they reverse direction but they do not greatly decelerate.

therefore your -25kgm/s will not affect the motion of the pipe after it leaves the turnaround , because its not in contact with the pipe , and it does not press upon the pipe.

it would only affect the momentum of the pipe if the pipe
were applying a force to accelerate or decelerate it.

and lets not forget that the 2 masses at the ends cancel each other out , they will slightly slow down while passing through the turnarounds however ,and that -force could be used as a negative toward pipe momentum , but what you have posted is not valid according to newtons laws of motion.

so what you end up with is

1) a force is applied for 500 ft to a mass and that mass is accelerated to a given velocity.
2) when that mass reaches the turnaround and passes through the turnaround it will apply a force that would reduce pipe momentum , however that mass is not being stopped only decelerated slightly.


and then that mass free floats for 500 ft back to the other turnaround and passes through the turnaround and it will apply a force that would increase pipe momentum , however that mass is not being stopped only decelerated slightly.

the mass is then accelerated again for a distance of 500 ft

and you didnt mention that there is a constant acceleration of 20 masses as the above is occurring that provides for pipe movement.


Quote:
Yep. If an object just turns around, then its moment becomes the negative of what it was before. Bounce a ball against a wall, and it's direction changes to negative, but its speed remains roughly the same. It's lost TWICE the momentum it had.



but the above would not apply to to pipe momentum , only the mass momentum , I thought that you understood that , I guess I was wrong because you seem to think otherwise or at least you would like for people to think that it would cause the pipe to not move , but as usual you are wrong again.


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Quote:
Correct, but they are not changing the angular momentum of
the whole system (ISS + gyroscopes).



but they are changing the momentum of the iss.

otherwise why would they even use it.



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Im not sure why Im answering your post

but you seem to think that a gyroscope will not change the momentum of a spacecraft.

corect?

if your spacecraft is spinning and then you stabilize the spacecraft by rotating the gyroscope and the spacecraft stops spinning then the gyroscope has changed the momentum of the spacecraft.

a student spinning by applying a force to a gyroscope

if the above student were inside a can in space he could use the gyroscope to manuver the can , much like space craft use them.

he applies a force to rotate the gyroscope then another to change the axis of he gyroscope in order to move himself and the gyroscope while standing on a swivel.

notice that no one pushes him and causes him to move by applying an external force on him or the swivel or the gyroscope , so if he were in a can in space this internal force he applies would rotate the can he is standing on.

just as newton describes it.
but not as imagegeek describes it.







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Quote:
He's saying the center of mass won't move. Which is what he said. The pipe can still move, just not the center of mass of it and its contents.


are you also him?
if not why are you replying to questions I ask him?

he has never said that the pipe would move.

remember imagegeek your entire argument is based on newtons laws as you understand them , so if the pipe cannot move without an external force applied to it , then the iss also cannot move without an external force applied to it.

and if the gyroscope was not turning then the ship would turn therefore the gyroscope is applying a force from inside the ship to keep the iss from turning.

pretty simple stuff.




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Quote:

- An accelerated mass starts with momentum p1.
- After acceleration at force F for time t it ends up with momentum p1+F*t. The reaction has the opposite effect on the pipe,


if I drive a car from new york to california then I apply the brakes and stop the car , does it require as much force to stop the car as it did to get the car to californa from new york?

no it doesnt.

and if there are 19 people driving 19 cars behind me at the same time , and Im only stopping 1 car.

is the force required to stop my 1 car the exact force being used to push the other 19 cars to californa?

no , it isnt.


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Quote:
Now I've shown no long-term movement with 2 masses, you can expand the calculation for 20 masses. But why 20? Why not 10? 100? 2?


nope , you didnt show anything except that you have a clear understanding in how to sudgest something will not work using incorrect assumptions.

we are using 20 masses because that is what we started with.

20 masses being accelerated will push the pipe with a greater force than 1 mass being accelerated.

besides I didnt want you two guys to get a even start so
I used 20 to start with.

we could use just 1 mass to prove it will work, and you know it.


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Originally Posted By: paul

but they are changing the momentum of the iss.

Yes.

Of course here 'iss' means the rest of the space station, excluding the gyroscopes themselves.

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Originally Posted By: paul
besides I didnt want you two guys to get a even start so
I used 20 to start with.


This is just a game to you? In other words you know you're wrong.

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Originally Posted By: paul

we are not decelerating the masses yet , other than the slight deceleration as the masses pass through the turnarounds , sure they reverse direction but they do not greatly decelerate.


OK this statement shows that we simply have different interpretations of the meanings of words.

To a physicist, 'acceleration' includes a change in speed or direction. Look up wikipedia to get a more thorough picture. This is the same acceleration in F=ma so it's crucial that we use a consistent definition.




Quote:

the mass is then accelerated again for a distance of 500 ft


Is this how it works?:

1. Accelerate the mass, starts moving the pipe.
2. Turn it around, applies a force the wrong way.
3. Turn around again, applies the same force the opposite way.
4. Repeat.

The two turn-arounds cancel each other out. Leaving only the acceleration to propel the pipe?


Last edited by kallog; 06/19/10 04:00 AM.
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Originally Posted By: paul

the brakes and stop the car , does it require as much force to stop the car as it did to get the car to californa from new york?

no it doesnt.


It may require more or less force. This misuse of terminology can totally lead you in the wrong direction. Of course you can gently accelerate with a tiny force and slowly get up to a high speed. Then crash into a tree with a huge force to stop. Much higher stopping force than starting force.

Equally you can floor it to accelerate with high force, then coast to a stop with a small force.

However the total impulse used to stop the car is the same as the total impulse used to start it. That's symmetric.


On the straight open road the force from the engine balances the force of friction, leaving no net force, and no acceleration - just constant velocity. So that section of the trip can be ignored.

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Quote:

but they are changing the momentum of the iss.

Quote:

Yes.

Of course here 'iss' means the rest of the space station, excluding the gyroscopes themselves.



so you unlike imagegeek realize that a internal force can
change the momentum of the iss.

closing his erroneus argument that an external force is required.


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Quote:
This is just a game to you? In other words you know you're wrong.


No , this is just a discussion to me.

I know I'm right.

and

I know you guys are wrong.


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Quote:
To a physicist, 'acceleration' includes a change in speed or direction. Look up wikipedia to get a more thorough picture. This is the same acceleration in F=ma so it's crucial that we use a consistent definition.



I have a clear understanding of that , and physicist also use decelerate to describe using a force to decelerate a object.

picking at straws are we?

Quote:
Is this how it works?:

1. Accelerate the mass, starts moving the pipe.
2. Turn it around, applies a force the wrong way.
3. Turn around again, applies the same force the opposite way.
4. Repeat.

The two turn-arounds cancel each other out. Leaving only the acceleration to propel the pipe?


but closer to

1. accelerate 20 masses applies 20 positive forces.
2. turn 1 mass around 180 degrees applies a negative force.
3. turn 1 mass around 180 degrees applies a positive force.
4. the 20 opposing masses are free floating applies zero force negative or positive.

5. repeat.

the result of this is constant acceleration of the pipe

even after the pipe has traveled the lenght of the pipe.

or the lenght of a billion pipes or a trilion pipes

as long as you have the electricity to supply an

acceleration to the 20 masses.





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Originally Posted By: paul
internal force can change the momentum of the iss.


I can't believe you're having trouble with this. Although most of the ISS changes its angular momentum, the total angular momentum of the ISS and its contents doesn't change. This is analogous to the total linear momentum of the tube and it's contents, which also doesn't change.



Gyro goes one way, rest of ISS goes the other way.

Masses go one way, tube goes the other way.

Gyro keeps spinning indefinately, rest of ISS keeps spinning indefinately.

Masses must reverse direction within the length of the tube, tube reverses direction.

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