Welcome to
Science a GoGo's
Discussion Forums
Please keep your postings on-topic or they will be moved to a galaxy far, far away.
Your use of this forum indicates your agreement to our terms of use.
So that we remain spam-free, please note that all posts by new users are moderated.


The Forums
General Science Talk        Not-Quite-Science        Climate Change Discussion        Physics Forum        Science Fiction

Who's Online
0 registered (), 258 Guests and 3 Spiders online.
Key: Admin, Global Mod, Mod
Latest Posts
Top Posters (30 Days)
Page 2 of 22 < 1 2 3 4 ... 21 22 >
Topic Options
#40026 - 09/09/11 02:22 AM Re: Record Cold in New Zealand 1903 -26.6 C [Re: paul]
kallog Offline
Megastar

Registered: 03/17/10
Posts: 1100
Originally Posted By: paul
I ask you WHERE DOES THE MASS STOP?

It doesn't stop. This is why I said adding momentum is important. -1 + 1 = 0. Total is 0, but each part is non-zero.




Quote:

how would you add momentum then.

0+0=0 ?

would the total momentum of the spacecraft be zero even though the spacecraft is moving at 1000 kph?


You have to include the momentum of the exhaust. You have to include everything that interacts with the spacecraft in order to ensure momentum is conserved.

momentum_exhaust + momentum_craft = 0

That's not 0 + 0 = 0. I don't know why you're making ridiculous statements like the momentum of the spacecraft is zero. It's clearly moving so it's non-zero.

That's true throughout the acceleration and continues to be true while it's coasting.


Edited by kallog (09/09/11 02:24 AM)

Top
.
#40027 - 09/09/11 02:36 AM Re: Record Cold in New Zealand 1903 -26.6 C [Re: paul]
kallog Offline
Megastar

Registered: 03/17/10
Posts: 1100
I think I'm saying things you don't understand. Can you answer these questions to check?


What do I mean by "system"

What does "total" mean in "total momentum"

What is the meaning of a negative momentum?

If object A has momentum pA and object B has momentum pB, what is the total momentum of the system comprising A and B?
a) pA + pB
b) pA - pB
b) |pA| + |pB|
c) 0
d) Requires more information to answer

Top
#40040 - 09/09/11 02:44 PM Re: Record Cold in New Zealand 1903 -26.6 C [Re: kallog]
paul Offline
Megastar

Registered: 03/21/06
Posts: 4136
Quote:
It's clearly moving so it's non-zero


correct.

Quote:
That's not 0 + 0 = 0. I don't know why you're making ridiculous statements like the momentum of the spacecraft is zero. It's clearly moving so it's non-zero.


simply because in the earlier attempts to explain that reactionless propulsion is possible you and others on this forum were always saying that the pipe would either never move at all , or that it would just wobble back and forth and never really go anywhere , thats why.

if you want me to understand the way your thinking then you should answer the questions below yourself.

Quote:
What do I mean by "system"

What does "total" mean in "total momentum"

What is the meaning of a negative momentum?

If object A has momentum pA and object B has momentum pB, what is the total momentum of the system comprising A and B?
a) pA + pB
b) pA - pB
b) |pA| + |pB|
c) 0
d) Requires more information to answer


then I will know.

but I do know that total momentum means all 3 stages in a 3 stage event.

not just a few hand picked stages to suit you.

like in the first 3 stages in the first event.

+1 pipe due to the -1 mass acceleration
-1 pipe due to the mass reverse in direction in the 1st turn
+1 pipe due to the mass reverse in direction in the 2nd turn

simple addition shows that the pipe would have momentum.

(+1) + (-1) + (+1) = +1 pipe momentum.

you have never agreed that the total momentum of the first three stage event would result in the pipe having momentum just like the spacecraft after it runs out of fuel.







_________________________
3/4 inch of dust build up on the moon in 4.527 billion years,LOL and QM is fantasy science.

Top
#40042 - 09/09/11 03:41 PM Re: Record Cold in New Zealand 1903 -26.6 C [Re: paul]
kallog Offline
Megastar

Registered: 03/17/10
Posts: 1100
Originally Posted By: paul
if you want me to understand the way your thinking then you should answer the questions below yourself.


What do I mean by "system"
All the things that interact with the pipe, including the pipe itself, the accelerator, the mass, the turns, etc. Most of them are fixed together so I treat it as just two parts - the mass and the pipe (with all its attachments).


What does "total" mean in "total momentum"
The sum of the momentums of all the parts in the system at some specified point in time.

What is the meaning of a negative momentum?
Moving in the opposite direction to what something with positive momentum would be.

If object A has momentum pA and object B has momentum pB, what is the total momentum of the system comprising A and B?
a) pA + pB



Quote:

but I do know that total momentum means all 3 stages in a 3 stage event.

Let's not call it total when adding changes in momentum through time. If you're thinking it's this and I'm thinking it's all at one time, then we can't communicate.

Forget that old thread where I did that - I already said I'd made a mistake with the numbers, so the whole list of additions is meaningless.



Edited by kallog (09/09/11 03:42 PM)

Top
#40043 - 09/09/11 03:47 PM Re: Record Cold in New Zealand 1903 -26.6 C [Re: kallog]
kallog Offline
Megastar

Registered: 03/17/10
Posts: 1100
Now those things are clarified lets analyze the system again:

1) Before it starts the mass is stationary and the pipe is stationary:
pMass = 0
pPipe = 0
pTotal = 0 + 0 = 0

2) After the first acceleration the mass is moving and the pipe is moving in the opposite direction:
pMass = -1
pPipe = 1
pTotal = -1 + 1 = 0

3) After the first turn the mass has the same speed but opposite direction.
pMass = 1
pPipe = ?
pTotal = 1 + ? = ?

Top
#40044 - 09/09/11 04:38 PM Re: Record Cold in New Zealand 1903 -26.6 C [Re: kallog]
paul Offline
Megastar

Registered: 03/21/06
Posts: 4136
3) After the first turn the mass has the same speed but opposite direction.
pMass = 1
pPipe = 0
pTotal = 1 + 0 = 1

the mass presents its entire momentum to the pipe as it passes through the 1st turn.
this will cause the pipe to stop just as if the mass would stop the pipe if it were suddenly stopped by the pipe as it left the accelerator.

the pipe is not moving but the mass inside the pipe is.
and I will continue to the 2nd turn

4) After the second turn the mass has the same speed but opposite direction.
pMass = -1
pPipe = 1
pTotal = -1 + 1 = 0

the pipe is now moving and the mass is still moving.


the first 3 stage event is now complete.

the pipe is moving and the mass is moving but in opposite directions.

the pipe has a momentum of 1 in one direction
the mass has a momentum of 1 in the opposite direction.

action / reaction

to continue to the next stage in the 2nd event.

the mass will be accelerated from -1 to -2
the pipe will accelerate from 1 to 2

moving on to after the 2nd turn in the second event of 3 stages.

you would have paid the energy cost to accelerate the mass to -2 and in turn the pipe would have accelerated to 2

action / reaction

but the mass is still moving and has a momentum of -2 before it enters the accelerator in the 3rd event of 3 stages.

you paid for 2
you now have 4

the 3rd event of 3 stages

you paid for 3
you now have 6

so on and so on...it doubles every event of 3 stages.

so in effect you can generate all the energy you paid by capturing the momentum of the mass after the mass leaves the 1st turn and not stop the spaceship or before it enters the accelerator and stop the spaceship.

you could let the spaceship just coast in space forever
and still have enought energy stored up to use to stop the spaceship.

your trip did not cost any energy and your spaceship has traveled a distance.

I told you I was right.





_________________________
3/4 inch of dust build up on the moon in 4.527 billion years,LOL and QM is fantasy science.

Top
#40058 - 09/10/11 03:24 AM Re: Record Cold in New Zealand 1903 -26.6 C [Re: paul]
kallog Offline
Megastar

Registered: 03/17/10
Posts: 1100
Quote:

2) After the first acceleration the mass is moving and the pipe is moving in the opposite direction:
pMass = -1
pPipe = 1
pTotal = -1 + 1 = 0


Originally Posted By: paul
3) After the first turn the mass has the same speed but opposite direction.
pMass = 1
pPipe = 0
pTotal = 1 + 0 = 1

the mass presents its entire momentum to the pipe as it passes through the 1st turn.
this will cause the pipe to stop just as if the mass would stop the pipe if it were suddenly stopped by the pipe as it left the accelerator.


You say the mass's momentum changes by +2 units and the pipe's momentum changes by -1 units. Why the discrepancy?

Whatever momentum the mass transfers to the pipe, the pipe has to receive from the mass. If the mass gains 2, the pipe has to lose 2.


Another way to look at it:
Imagine the pipe and mass both have the same mass.
In step 2 it's effectively two identical objects travelling towards each other at the same speed.
You say that when they hit and bounce off, _one_ of them stops, while the other changes direction. How do you know which one stops and which one reverses?

Top
#40070 - 09/10/11 08:26 PM Re: Record Cold in New Zealand 1903 -26.6 C [Re: kallog]
paul Offline
Megastar

Registered: 03/21/06
Posts: 4136
Quote:
You say the mass's momentum changes by +2 units and the pipe's momentum changes by -1 units. Why the discrepancy?


well if you are speaking about a mass that is moving in one direction , then it changes its direction to the opposite direction then yes it does change by 2 units but not by +2 units.

while the mass travels through the 1st turn its momentum
changes from -1 to 0 through the 1st half of the 1st turn.
then as the mass travels from half way through the 1st turn until it finishes passing through the 1st turn the mass
changes its momentum from 0 to +1

its momentum has changed 2 units but it never did achieve
a +2 momentum change in either the (-) or the (+) direction.

Quote:
Whatever momentum the mass transfers to the pipe, the pipe has to receive from the mass. If the mass gains 2, the pipe has to lose 2.


Whatever momentum the mass transfers to the pipe, the pipe has to receive from the mass. TRUE

If the mass gains 2, the pipe has to lose 2.
you mean if the accelerator causes the mass to gain 2 in one direction the pipe has to gain 2 in the opposite direction.

To every action there is always an equal and opposite reaction: or the forces of two bodies on each other are always equal and are directed in opposite directions.

http://www.youtube.com/watch?v=L2mdAvdPhT4

when the ball that is attached to the string in the pendulum example in the above MIT video is dropped the ball transfers its momentum to the table and the ball would not just stop when it is half way through the pendulum.

No it wouldnt . the ball does not stop it keeps going and the only reasons the ball does not go as high as the position it was dropped from is gravity and a small amount of air resistance.

so the ball on the string pulls on the string.
the pole that the string is attached to pushes downward on the table and this push is a force caused by the ball swinging on the string.

just like the mass passing through the 1st turn.
except the pipe is moving, so as the mass passes through the 1st turn the mass applies a force to the pipe, and this force stops the pipe.

if the pipe were not moving , and the mass passed through the 1st turn , then the pipe would move in the (-) direction and the mass would stop.

because the pipe would not have momentum and the mass would have momentum , the mass would transfer its momentum to the pipe.

just like a pool ball transfers all of its momentum to another pool ball if struck at just the correct angle.

Quote:
Another way to look at it:
Imagine the pipe and mass both have the same mass.
In step 2 it's effectively two identical objects travelling towards each other at the same speed.


No the mass and the pipe have different speeds.
wasnt the mass 100kg and the pipe 1000kg before I changed the pipe length to 1000 meters vs 500 ft.

so the force that is applied to accelerate the 100kg mass could not accelerate the 1000kg pipe and the 100kg mass to the same speed.

Quote:
You say that when they hit and bounce off, _one_ of them stops


yes the one that has +1 momentum stops , its the pipe , it stops.
it stops because of the -1 momentum of the mass.

the mass continues moving because the pipe is also transfering momentum to the mass while the mass is transfering momentum to the pipe.

no other energy is expended durring the collision such as bending the pipe or the mass or in general deforming the mass or the pipe.

now remember this is in space , so just like the spacecraft that exhaust its thrust the mass would keep going forever if it didnt encounter the 1st turn.

but its a little different because the acceleration of the mass gave the pipe the exact same amount of momentum that the mass recieved , so before they collide the two had 2 units of momentum between them.

so we started with 2 units , -1 mass and +1 pipe.
durring the collision we used up 1 unit stopping the pipe
and after the 1st turn we end up with 1 unit , which is the +1 momentum of the mass.

so the 2nd turn should stop the mass as it passes through the 2nd turn.

this means that the accelerator may have to extend into the 2nd turn just a little so that the mass will enter the accelerator.

we still have the following after the completion of the first 3 stage event.

1) acceleration +1 pipe , -1 mass
2) 1st turn 0 pipe , +1 mass
3) 2nd turn +1 pipe , 0 mass

the pipe moves durring the acceleration , then stops
then the pipe moves durring the 2nd turn.

the pipe is moving and the mass is not.


theres really nothing odd about that.

if your worried about the free energy part of it just think about this.

if all you have is a straight rail gun in space.

you shoot a 100kg mass from a 100kg rail gun
what do you have?

you have 2 masses with the same exact momentum.
one mass goes in one direction the other mass goes in the opposite direction.

now if that rail gun were inside a long pipe and the mass and rail gun strike the ends of that pipe at the same time you would have 2 impacts that would total to twice the amount of energy you supplied to fire the rail gun.

you could capture that energy and that would be free energy
because you got back the energy you expended and you also got back an equal amount of energy to boot.

To every action there is always an equal and opposite reaction: or the forces of two bodies on each other are always equal and are directed in opposite directions.

but thats not how that works.
when the rail gun pushes against the mass 1/2 the energy is expended to push the mass and 1/2 the energy is expended to push the rail gun.

so in reality you could only capture the same amount of energy that you expended.

but both masses moved a distance and it cost you nothing.

that is still free energy because you moved things a distance and it cost you nothing.



















_________________________
3/4 inch of dust build up on the moon in 4.527 billion years,LOL and QM is fantasy science.

Top
#40071 - 09/11/11 01:22 AM Re: Record Cold in New Zealand 1903 -26.6 C [Re: paul]
kallog Offline
Megastar

Registered: 03/17/10
Posts: 1100
Originally Posted By: paul
well if you are speaking about a mass that is moving in one direction , then it changes its direction to the opposite direction then yes it does change by 2 units but not by +2 units.

I agree with the first part. But obviously 2 = +2 so the last line is nonsense.


Quote:

while the mass travels through the 1st turn its momentum
changes from -1 to 0 through the 1st half of the 1st turn.
then as the mass travels from half way through the 1st turn until it finishes passing through the 1st turn the mass
changes its momentum from 0 to +1

I agree

Quote:

its momentum has changed 2 units but it never did achieve
a +2 momentum change in either the (-) or the (+) direction.

Internal contradiction. Please use common terminology or different words so I know what you're trying to say. "momentum changed 2 units" is the same as "achieved a +2 momentum change" to me. Do you mean it never achieves a momentum of +2?



Quote:
Whatever momentum the mass transfers to the pipe, the pipe has to receive from the mass. TRUE

[quote]
If the mass gains 2, the pipe has to lose 2.
you mean if the accelerator causes the mass to gain 2 in one direction the pipe has to gain 2 in the opposite direction.

Yes. However we decided our accelerator only causes the mass to gain 1 in the negative direction (ie lose 1).


So you seem to agree with me but your conclusion is different. I say:

2)
After the 1st turn:
The mass has momentum +1
The pipe has momentum -1
The total momentum is +1 + -1 = 0

You say:

2)
After the 1st turn:
The mass has momentum +1
The pipe has momentum 0
The total momentum is +1 + 0 = +1


The mass gains 2, the pipe loses 1. Disagrees with what you said above.

Top
#40072 - 09/11/11 02:05 AM Re: Record Cold in New Zealand 1903 -26.6 C [Re: kallog]
paul Offline
Megastar

Registered: 03/21/06
Posts: 4136
Quote:
Yes. However we decided our accelerator only causes the mass to gain 1 in the negative direction (ie lose 1).


I dont consider a gain in momentum a loss in momentum.
I only consider that the mass gains momentum as it is pushed down the accelerator.

it might accelerate in the negative direction in respect to the entire system but it is not a loss of momentum.


Quote:
After the 1st turn:
The mass has momentum +1
The pipe has momentum -1
The total momentum is +1 + -1 = 0


well when I use momentum I mean momentum.
something that is not moving has no momentum.

it appears that when you use momentum you cant decide what momentum is.

what does the sentence below mean to you?

The pipe has momentum -1

knowing that a momentum of -1 would be saying that the pipe is moving in the negative direction with a magnatude of 1

from what I can tell AFTER the 1st turn the pipe would stop.

are you saying that the pipe would not stop after the 1st turn?


Quote:
while the mass travels through the 1st turn its momentum
changes from -1 to 0 through the 1st half of the 1st turn.
then as the mass travels from half way through the 1st turn until it finishes passing through the 1st turn the mass
changes its momentum from 0 to +1

I agree


its obvious that you agree that the mass will pass through the 1st turn , so if you are trying to say that the pipe will go from a +1 momentum to a -1 momentum then you are just wrong.

and what I mean above is that you would be saying that the pipe itself would go from a
+ direction with a magnatude of 1
to a
- direction with a magnatude of 1

a mass with a momentum of 1 cannot create 2 momentums
that are equal in magnatude in a collision.

what is happening in the 1st turn is that as the mass passes through the 1st half of the 1st turn the mass transfers 1/2 of its momentum force to the pipe.
and
as the mass passes through the 2nd half of the 1st turn the mass transfers the other 1/2 of its momentum force to the pipe.


and
as the mass passes through the 1st half of the 1st turn the pipe transfers 1/2 of its momentum force to the mass.
and
as the mass passes through the 2nd half of the 1st turn the pipe transfers the other 1/2 of its momentum force to the mass.

in a collision momentums are transfered from one body to the other.

so the pipe stops.

it may even be that the mass doubles its momentum as it passes through the 1st turn.

and the mass would then have a +2 momentum.

this way momentum would be conserved.

because it started with 2 units of momentum only in different directions and because the pipe is moving towards the mass the pipe may accelerate the mass even further as the pipe stops.

yes I think that is what would happen.

then the mass free floats to the 2nd turn.

then the mass with a + direction and a magnatude of 2
passes through the 2nd turn and causes the pipe to have a momentum in the + direction and 1/2 of the mass momentum is transfered into the pipe and the mass decelerates through
the 2nd turn and ends up with a -1 momentum.

this makes much more sense.




_________________________
3/4 inch of dust build up on the moon in 4.527 billion years,LOL and QM is fantasy science.

Top
#40073 - 09/11/11 04:15 AM Re: Record Cold in New Zealand 1903 -26.6 C [Re: paul]
kallog Offline
Megastar

Registered: 03/17/10
Posts: 1100
Originally Posted By: paul
I only consider that the mass gains momentum as it is pushed down the accelerator.

When I say "gains momentum" I mean "momentum becomes more positive". I'll try to use that wording from now on.


Quote:

what does the sentence below mean to you?

The pipe has momentum -1

knowing that a momentum of -1 would be saying that the pipe is moving in the negative direction with a magnatude of 1

Yes.

Quote:

are you saying that the pipe would not stop after the 1st turn?

Yes

Quote:
so if you are trying to say that the pipe will go from a +1 momentum to a -1 momentum

Yes




Quote:

what is happening in the 1st turn is that as the mass pipe
...
transfers the other 1/2 of its momentum force to the mass.

Be precise. There's no such thing as "momentum force". This kind of detail is why we're having so much trouble communicating.



Quote:

because it started with 2 units of momentum only in different directions and because the pipe is moving towards the mass the pipe may accelerate the mass even further as the pipe stops.

No no, absolutely not. Momentum is a vector. So when you add momentums you have to do vector addition. In 1D that means -1 + +1 = 0. It does not mean |-1| + |+1| = 2. No way.

-----

How about apply conservation of energy. There's no way you can doubt it's applicability to a simple 1D elastic collision, which is what we have.

You say:

Before the 1st turn
the mass has kinetic energy X
the pipe has kinetic energy Y > 0
Total kinetic energy = X+Y

After the 1st turn
the mass has kinetic energy X
the pipe has kinetic energy 0
Total kinetic energy = X

Kinetic energy has been reduced by Y. We have no friction or other energy loss. So this is impossible.

Top
#40080 - 09/11/11 02:02 PM Re: Record Cold in New Zealand 1903 -26.6 C [Re: kallog]
paul Offline
Megastar

Registered: 03/21/06
Posts: 4136
Quote:
what does the sentence below mean to you?

The pipe has momentum -1

knowing that a momentum of -1 would be saying that the pipe is moving in the negative direction with a magnatude of 1

Yes.


remember this

Quote:
Whatever momentum the mass transfers to the pipe, the pipe has to receive from the mass. If the mass gains 2, the pipe has to lose 2.



Quote:
"momentum becomes more positive".


how does momentum become more positive?
does a gain in momentum require a external force?
you say the pipe that has a magnatude of momentum of 1
and a direction of + will both decelerate to zero momentum
and then accelerate in the opposite direction with a magnatude of momentum of 1 and a direction of -

the mass only has a momentum magnatude of -1
the mass would need a momentum maganatude of -2
to both decelerate the pipe to zero momentum and
then accelerate the pipe to -1.

where did you get the extra force to accelerate the pipe in the opposite direction once the pipe stopped.

or are you saying that the pipe does not need to stop , it just magically switches directions without first stopping?





Quote:
Momentum is a vector


so how can a vector cause the pipe to stop , start , reverse directions , etc , if there is no force involved?

are you saying that a vector is a force?

In classical mechanics, momentum SI unit kgm/s, or, equivalently, Ns is the product of the mass and velocity of an object (). Like velocity, momentum is a vector quantity, possessing a direction as well as a magnitude.

Quote:
There's no such thing as "momentum force". This kind of detail is why we're having so much trouble communicating.


there is such a thing as momentum force , thats why momentum is given the symbol p in physics.

if momentum was not a force then you would not use p in equations as in below.



Momentum was not merely the motion, which was motus, but was the power residing in a moving object

In physics, power is the rate at which work is performed or energy is converted.

In physics, work is the amount of energy transferred by a force acting through a distance in the direction of the force.

the result of 2 objects that are not accelerating that collide would be quantified by using p ( the force of momentum ) , otherwise just what would you propose to use
in an equation to calculate the force of the 2 objects colliding.

let me go back and find where you have used p ( momentum )
in this thread.

yes just a few post back you used momentum as if it was a force , exactly the way it is supposed to be used as the momentum of an object is the mass x its velocity.

its velocity includes its direction.

Quote:
What is the meaning of a negative momentum?

If object A has momentum pA and object B has momentum pB, what is the total momentum of the system comprising A and B?
a) pA + pB
b) pA - pB
b) |pA| + |pB|
c) 0
d) Requires more information to answer


so in the above that you posted earlier you used p for momentum.

what specificaly were you meaning above by
pA + pB ?

its obvious that an A and an B cannot add up because you cannot add the letters in the alphabet.
so the letters A and B must be describing the momentum of the 2 objects.

so if you were to describe the resultant force due to a collision of 2 objects which words would you use.

the force of momentum.
or what?


Quote:
Quote:

because it started with 2 units of momentum only in different directions and because the pipe is moving towards the mass the pipe may accelerate the mass even further as the pipe stops.

No no, absolutely not. Momentum is a vector. So when you add momentums you have to do vector addition. In 1D that means -1 + +1 = 0. It does not mean |-1| + |+1| = 2. No way.


Im begining to wonder if you have a clue as to what happens in the real world.

when I said 2 units of momentum that is exactly what I meant.

the pipe has 1 unit , the mass has 1 unit , when they collide the collision will be the product of the 2 units of momentum.

is there a zero in your vector addition?

do your vector graphs have a zero?

do a vector graph of your car going from 0 - 10 mph
then the car goes from 10 - 0 mph

then the car is put into reverse and backs up from 0 to -10 mph

I want to see if you really believe yourself.











_________________________
3/4 inch of dust build up on the moon in 4.527 billion years,LOL and QM is fantasy science.

Top
#40087 - 09/12/11 03:26 AM Re: Record Cold in New Zealand 1903 -26.6 C [Re: paul]
kallog Offline
Megastar

Registered: 03/17/10
Posts: 1100
Quote:

a momentum magnatude of -1

You still don't know what magnitude means? Why don't you look things up instead of forcing yourself to remain confused?


Momentum is not force. If it was we'd call it force instead of momentum.

This is a 1-dimensional elastic collision! Nothing could be simpler. This is what teenage science students do every day. I think you just need to do some study.

Or get two coins and slide them against each other on a smooth table top.


Summary
~~~~~~~
I a 1D elastic collision:

I say - total momentum before = total momentum after

You say - sum of magnitides of momentums before = sum of magnitudes of momentums after.

Top
#40102 - 09/12/11 03:42 PM Re: Record Cold in New Zealand 1903 -26.6 C [Re: kallog]
paul Offline
Megastar

Registered: 03/21/06
Posts: 4136
Quote:
You still don't know what magnitude means? Why don't you look things up instead of forcing yourself to remain confused?


http://en.wikipedia.org/wiki/Momentum

Quote:
In classical mechanics, momentum (pl. momenta; SI unit kgm/s, or, equivalently, Ns) is the product of the mass and velocity of an object (). Like velocity, momentum is a vector quantity, possessing a direction as well as a magnitude.


in the above what do you think the product is?

I know what the magnatude is , but we decided to use symbols such as +1 or -1 or 0 in lieu of using actual momentum such as 4000 kg m/s
so when I say +1 I mean 4000 kg m/s in the + direction.

Quote:
I a 1D elastic collision:

I say - total momentum before = total momentum after

You say - sum of magnitides of momentums before = sum of magnitudes of momentums after.


kallog the sum of magnatudes is the total momentum.

Quote:
Or get two coins and slide them against each other on a smooth table top.


you would like that wouldnt you , two exact sized coins and propel them at the exact same speed towards each other.

that would prove that you would get a reversing pipe , but dont forget that the pipe is 1000 kg and the mass is 100 kg

and the mass has a speed of 40 m/s and the pipe has a speed of 4 m/s

the total momentum before the first turn is 8000 N.s

4000><4000

quite a difference there kallog ,

if the two were meeting head on they would bounce off as in your coin bouncing trick.

but thats not the case here , the mass is being propeled through a turn.

this causes the pipe with a speed of 4 m/s to stop.
and since the mass with a speed of 40 m/s is not stopping because it is traveling through a turn the mass is accelerated to an even higher speed by the momentum of the pipe.

before you had 4000><4000
now you have 8000< and 0

so the mass is now traveling at 80 m/s
so its momentum has doubled.

100 kg x 80 m/s = 8000 N.s

however it complies with conservation of momentum
and all other physical laws.

this isnt school book stuff but that is probably why you cant find it on the internet and why people just dont understand it when they come across it.

I dont understand why you cant understand this however unless your just trying to get people to think it wouldnt work so that you can become the inventor of it.

think of it as a backwards gravity assist only that in this case the mass is not being accelerated by a pull of gravity it is being accelerated by a push of the pipe as it makes its way through the turn.



in the above the green planet is moving in the direction of the arrow.
the spacecraft is being pulled toward the planet as it makes the turn.
this accelerates the spacecraft.

so just think of the pipe moving in the same direction as the planet is moving , there really is no difference between a pull or a push , and the mass cant tell a difference either.

http://en.wikipedia.org/wiki/Gravity_assist

Quote:
Suppose that you are a "stationary" observer and that you see: a planet moving left at speed U; a spaceship moving right at speed v. If the spaceship has the proper trajectory, it will pass close to the planet, moving at speed U + v relative to the planet's surface because the planet is moving in the opposite direction at speed U. When the spaceship leaves orbit, it is still moving at U + v relative to the planet's surface but in the opposite direction, to the left; and since the planet is moving left at speed U, the total velocity of the rocket relative to you will be the velocity of the moving planet plus the velocity of the rocket with respect to the planet. So the velocity will be U + ( U + v ), that is 2U + v.










_________________________
3/4 inch of dust build up on the moon in 4.527 billion years,LOL and QM is fantasy science.

Top
#40113 - 09/13/11 06:04 AM Re: Record Cold in New Zealand 1903 -26.6 C [Re: paul]
kallog Offline
Megastar

Registered: 03/17/10
Posts: 1100
Originally Posted By: paul
in the above what do you think the product is?

It means mass x velocity


Quote:
kallog the sum of magnatudes is the total momentum.


We don't need to go any further until you work this out. Otherwise it's a waste of time.

pMass = -1
pPipe = 1

"the sum of the magnitudes of the momentums" = |-1| + |1| = 2
"the sum of the momentums" = -1 + 1 = 0

Both are correct, but only one is conserved.

Top
#40114 - 09/13/11 06:08 AM Re: Record Cold in New Zealand 1903 -26.6 C [Re: kallog]
kallog Offline
Megastar

Registered: 03/17/10
Posts: 1100
By the way I made a small mistake about the individual momentums after the 1st turn. It's not +1 and -1 (nor +2 and 0). But I won't tell you until you work it out.

Top
#40122 - 09/13/11 06:34 PM Re: Record Cold in New Zealand 1903 -26.6 C [Re: kallog]
paul Offline
Megastar

Registered: 03/21/06
Posts: 4136
Quote:
It means mass x velocity


but you still think that momentum is not a word that is used in place of the force that a moving object has due to its movement.

F = ma is mass times acceleration.

p = mv is mass times velocity

in a collision the ONLY DIFFERENCE is that momentum includes a direction.

if there is an accelerating object accelerating at 1 m/s
and a object that has a velocity of 40 m/s

and they both have a mass of 100 kg and they both impact another object at exactly 40 m/s in the same direction the momentum will be exactly the same at each impact.

so when your dealing with a moving object that is not accelerating you can and should use the force of momentum.
_________________________
3/4 inch of dust build up on the moon in 4.527 billion years,LOL and QM is fantasy science.

Top
#40123 - 09/13/11 06:38 PM Re: Record Cold in New Zealand 1903 -26.6 C [Re: kallog]
paul Offline
Megastar

Registered: 03/21/06
Posts: 4136
Quote:
By the way I made a small mistake about the individual momentums after the 1st turn. It's not +1 and -1 (nor +2 and 0). But I won't tell you until you work it out.


we never did get that far kallog.

thats ok kallog you dont have to tell me , I dont mind.

I will say this though , the total momentum will be 8000 N.s

because it started with 8000 N.s

anything under or over 8000 N.s will violate the laws of conservation of momentum.



_________________________
3/4 inch of dust build up on the moon in 4.527 billion years,LOL and QM is fantasy science.

Top
#40133 - 09/14/11 07:27 AM Re: Record Cold in New Zealand 1903 -26.6 C [Re: paul]
kallog Offline
Megastar

Registered: 03/17/10
Posts: 1100
Originally Posted By: paul
I will say this though , the total momentum will be 8000 N.s

because it started with 8000 N.s

anything under or over 8000 N.s will violate the laws of conservation of momentum.


Can you provide a reference to those laws? It's different from everything I've ever seen.


Here's common-sense proof it's wrong:

Two identical 1kg objects, each travelling at 4000m/s collide head on and stick together. After they stick together you say the 2kg blob will be moving at 4000m/s.

Please confirm that's what you predict to make sure I'm not misunderstanding you.

Top
#40134 - 09/14/11 07:50 AM Re: Record Cold in New Zealand 1903 -26.6 C [Re: kallog]
kallog Offline
Megastar

Registered: 03/17/10
Posts: 1100
This page disagrees with you. Can you explain why?

http://www.splung.com/content/sid/2/page/momentum

Look at the "explosion" animation at the bottom of the page. It violates your "law of conservation of magnitude of momentum".

The collision animation above it can be made to violate your law too. Change mB from 1kg to 3kg, then press play. The total momentum before is 1kg*2m/s = 2Ns. The sum of the magnitudes of momentum after is 1*1 + 3*1 = 4.

Top
Page 2 of 22 < 1 2 3 4 ... 21 22 >



Newest Members
debbieevans, bkhj, jackk, Johnmattison, RacerGT
865 Registered Users
Sponsor
Facebook

We're on Facebook
Join Our Group

Science a GoGo's Home Page | Terms of Use | Privacy Policy | Contact Us
Features | News | Books | Physics | Space | Climate Change | Health | Technology | Natural World

Copyright © 1998 - 2016 Science a GoGo and its licensors. All rights reserved.