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#40252 - 09/20/11 04:00 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
throw the theoretical laws into the theory can.


Right or wrong, those theories have given us cars and computers.

Millions of made-up ideas that were never tested, have internal inconsistencies and contradict observations of the real world (remember that inconvenient thing?) have given us nothing.

Again, if you're sure you're right, then you won't be talking about it, you will have already built it and will now be a Nobel prize winner who's also RICHER THAN GOD. No barrier is too great to stop you if you're confident enough. Your refusal to put your money where your mouth is proves that you don't believe your own words.

Top
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#40254 - 09/20/11 05:13 PM Re: Record Cold in New Zealand 1903 -26.6 C [Re: kallog]
paul Offline
Megastar

Registered: 03/21/06
Posts: 4136
Quote:
A change of direction has the same effect on the pipe as a stop? How can you possibly imagine that to be true? What if we stop it, then accelerate it in the opposite direction. Will that give +8000N while a U-bend is only +4000N?


Quote:
A change of direction has the same effect on the pipe as a stop? How can you possibly imagine that to be true?


the same effect on the pipes acceleration.
that effect is +4000N


Quote:
What if we stop it, then accelerate it in the opposite direction.Will that give +8000N


if we stop it
deceleration = +4000N pipe

then accelerate it in the opposite direction
acceleration = +4000N pipe

Will that give +8000N
yes , and it gives it to the pipe


Quote:
What if we stop it, then accelerate it in the opposite direction.Will that give +8000N while a U-bend is only +4000N?


the U-bend does not stop it.

it doesnt slow its velocity.

it still has its mass and its velocity

its momentum is +4000N

stopping an object completely and then re-accelerating that object requires more
force than simply changing its direction through a turn.

the force going into the turn was -4000N
the force going out of the turn is +4000N

I would think that because the mass has +4000N
as it leaves the turn , the pipe was only given -4000N
of the 8000N.

does you car require double the gas if you only drive around in a circle?



Quote:
Are you seriously saying that applying the same force for a longer time will give the same momentum to an object?


yes , if your using a spring that can only store a given amount of force.
you can spend 1 second , 1/2 second , 600,000,000 years or any amount of time you choose to compress the spring , it will only store the 40N

when you use the force stored in the spring , it wont matter how long the force is applied to the mass , because the 40N stored force is

40 kg m / 1 second
or
20 kg m / 2 seconds
or
10 kg m / 4 seconds

etc...etc...etc...

Quote:
As soon as you start applying the 40N to the (massless) spring, the solar sail immediately feels the full 40N and starts accelerating at a=40N/mass.


so if the solar sail has a mass of 1000000 kg
the acceleration would be
a=40N/1000000
.00004 m/s/s

wow thats fast.

now lets find its momentum !!

p=mv

1000000 x .00004 = 40N

YEP !!


Quote:
Your physics skills seem to be deteriorating.


from the looks of it it is your physics skills that need a little brushing up.
however your trickery skills are improving.

Quote:
I often go and research things so I know something about what I'm saying on internet forums.


ok , then you start doing that , if it will help.


meanwhile
would you like a few more?





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

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#40255 - 09/20/11 05:45 PM Re: Record Cold in New Zealand 1903 -26.6 C [Re: kallog]
paul Offline
Megastar

Registered: 03/21/06
Posts: 4136
Quote:
Right or wrong, those theories have given us cars and computers.


No they havent , they have stagnated technology.

besides , can anything be designed using only theories.

while

anything can be designed using only math.

Quote:
Millions of made-up ideas that were never tested, have internal inconsistencies and contradict observations of the real world (remember that inconvenient thing?) have given us nothing.

Again, if you're sure you're right, then you won't be talking about it, you will have already built it and will now be a Nobel prize winner who's also RICHER THAN GOD. No barrier is too great to stop you if you're confident enough. Your refusal to put your money where your mouth is proves that you don't believe your own words.


that sounds like a theory.

anyway were not discussing me or my finances or your theories were discussing this concept.

if you believe your theories are correct then why cant you prove that , this is the ideal place to do so.

theories are a part of physics ,and the math of physics is supposed to back up the theories.








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

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#40258 - 09/20/11 11:29 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
the U-bend does not stop it.

it doesnt slow its velocity.

Quote:

its momentum is +4000N

N is not a unit of momentum. So nothing can have a momentum of +4000N.

[quote]
the force going into the turn was -4000N
the force going out of the turn is +4000N

What are these forces acting on? Obviously the force on the mass is in the same direction, both going into the turn and coming out of it. Similarly for the force on the pipe.


Quote:

does you car require double the gas if you only drive around in a circle?

No it doesn't. But our system is frictionless, so the comparable car would require no gas, whether circling or doing a U-turn or bouncing off a spring, or even stopping with regenerative breaking, then accelerating again. Can you say anything that isn't completely misguided?


Quote:

you can spend 1 second , 1/2 second , 600,000,000 years or any amount of time you choose to compress the spring , it will only store the 40N

You're ignoring the part where the force used to compress the spring is also, at the same time, accelerating the sail. Springs don't make forces disappear. We already went through that argument before. If you don't believe me, break open a pen and try pushing the spring. Notice the force is transmitted right through. Use the spring to push something, the thing can be pushed via the spring.


Quote:

the 40N stored force is
40 kg m / 1 second

40N = 40 kg m / s^2
So no, those expressions are not equal.


Quote:

a=40N/1000000
.00004 m/s/s

p=mv
1000000 x .00004 = 40N

Force is not momentum. Velocity is not acceleration. Let's find its momentum after 2 seconds:
p=mv
p=ma*t
1000000 x .00004 x 2 = 80Ns

Let's find its momentum after 1000 seconds:
p=mv
p=ma*t
1000000 x .00004 x 1000 = 40,000Ns


Quote:

from the looks of it it is your physics skills that need a little brushing up.

This really is becoming bizarre. You have just made claims that can be disproved simply by playing with things in the real world. You absolutely havn't got a hope when it comes to physics. Look at all the corrections I made to your lies. Why didn't you try to actually understand what you're saying before saying it?


Just in case you didn't get it the other times:
Force is not momentum
Velocity is not acceleration

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#40259 - 09/20/11 11:34 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 believe your theories are correct then why cant you prove that , this is the ideal place to do so.


Haven't you seen all the messages I wrote to you? They explain why it can't work. They explain what it would do instead. They explain why your claims are wrong. What more do you need?

You need to find a new hobby. There's no possibility you can learn high school physics, or even observe the real world yourself - all this time and you haven't. Just give up.

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#40260 - 09/21/11 01:11 AM Re: Record Cold in New Zealand 1903 -26.6 C [Re: kallog]
paul Offline
Megastar

Registered: 03/21/06
Posts: 4136
Quote:
N is not a unit of momentum. So nothing can have a momentum of +4000N


then tell me what is a unit of momentum.
let me ask you a question , if a object that is not accelerating and has a velocity
of 40 m/s , what would its momentum be in your world.



this is really getting old , kallog

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

Quote:
In classical mechanics, momentum (pl. momenta; SI unit kgm/s, or, equivalently, Ns)


Quote:
Obviously the force on the mass is in the same direction, both going into the turn and coming out of it. Similarly for the force on the pipe.


you do understand that you just contradicted yourself by saying the mass has a force on it.

Quote:
No it doesn't. But our system is frictionless, so the comparable car would require no gas


thats true.

Quote:
require no gas, whether circling or doing a U-turn or bouncing off a spring, or even stopping with regenerative breaking, then accelerating again. Can you say anything that isn't completely misguided?


Quote:
even stopping with regenerative breaking, then accelerating again.


so now its just F=m

if it has mass you can accelerate it without a force.

Quote:
You're ignoring the part where the force used to compress the spring is also, at the same time, accelerating the sail.


Im not ignoring it , I said momentarily !

in fact here is what I said

Quote:
now apply a -40N force to the spring.
the solar sail feels the -40N force that you apply to the spring , and as you apply the -40N force the solar sails mass resist movement momentarily while you depress the spring.
but you have depressed the spring and if you hold it in with a -40 N force the sail will move away from you.


xxx

Quote:
If you don't believe me, break open a pen and try pushing the spring. Notice the force is transmitted right through. Use the spring to push something, the thing can be pushed via the spring.


just a minute.
it just so happens that I have one.
ok , now let me go outside to my truck.
........... time passes .....................
nope the truck didnt move !!!

but we were only using a 40N force stored in the spring vs
a 1000000 kg mass.

thats about right!!!

Quote:
40N = 40 kg m / s^2
So no, those expressions are not equal.


that would be a force of 40N.s
which would be like a mass x its acceleration.
we were talking about a spring.
the force that the spring can supply as it expands.
thats why I used N


Quote:
Force is not momentum. Velocity is not acceleration. Let's find its momentum after 2 seconds:
p=mv
p=ma*t
1000000 x .00004 x 2 = 80Ns

Let's find its momentum after 1000 seconds:
p=mv
p=ma*t
1000000 x .00004 x 1000 = 40,000Ns


kallog do you have any springs that you can apply a force to and get 2 times that force back by allowing the spring to expand in 2 seconds?

better yet I want the one that you can apply a force to and get 1000 times that force back by allowing the spring to expand in 1000 seconds?

thats awesome.

I think the problem here is that you are using a force that is constant over a period of time.

40N x 2 seconds = 80N
and
40N x 1000 seconds = 40,000N

that would be like you standing there re-compressing the spring every time it
expands .000000000000000000000000001 meters.

I am using a spring that does not deliver a constant force over a period of time.

the force that the spring delivers gets lower and lower as it expands.

so its not constant , its force gets consumed unlike what your using.

maybe we shouldnt use momentum.

because if I apply a force of 40N to a spring for 1 second
I should only be able to get 40N of force out of that spring
no matter how much time it takes for the spring to expand.

a spring is not a inexhaustable supply of force.

maybe it would be better to just ask you what word would you use to describe the amount of force that an object that isnt accelerating (but has a velocity) that collides with another object would generate?

you pick a word for us to use.

and it will represent the (force) that a moving object
(not a accelerating object) will place on another object.

this is really getting ridiculous , I cant help it that the stupid idiots that made the physics words didnt include a word for that so lets just make one up to use.

a word that can be used to describe the following

a 10 kg mass that is traveling at a speed of 1 meter per second (not meter per second per second) should have a
(the word we choose) of 10 kg m/s

if it strikes a wall it should deliver a
(the word we choose) of 10 kg m/s to the wall.

so that you can write a sentence like below describing the
(the word we choose) that the 10 kg m/s object applied to the wall.

a mass of 10 kg struck the wall traveling at 1 meter per second and generated a (the word we choose) of 10 kg m/s

we cant use force for the word because the object isnt accelerating.
because force is mass x acceleration.

we cant use momentum because momentum isnt a force.

so what word can we use?


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

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#40261 - 09/21/11 04:32 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
then tell me what is a unit of momentum.
unit kgm/s, or, equivalently, Ns


Quote:

let me ask you a question , if a object that is not accelerating and has a velocity
of 40 m/s , what would its momentum be in your world.

Use p=mv



Quote:

it just so happens that I have one.
ok , now let me go outside to my truck.
........... time passes .....................
nope the truck didnt move !!!

Do you know why? It's not directly because of the large mass of the truck. There are other factors which we don't have in the tube.


Quote:
40N = 40 kg m / s^2
So no, those expressions are not equal.


Quote:

that would be a force of 40N.s

Ararrh13!#@ Force does not have units of Ns!!!! That's momentum. Come on! Your own reference to Wikipedia agrees with me.


Quote:
kallog do you have any springs that you can apply a force to and get 2 times that force back by allowing the spring to expand in 2 seconds?

Expand? Why is the spring expanding? If you apply enough force to compress it, it'll remain compressed as long as the force is applied. It'll also move with the sail so you have to keep expending energy running after it applying that force.

Unless the force is reacted against the sail itself, then it won't keep accelerating the sail and won't keep consuming energy. Something like a latch that clamps the spring in compression.



Quote:
isnt accelerating (but has a velocity) that collides with another object would generate?
you pick a word for us to use.

Not enough information. It depends how much the objects deform. If the two bodies are rigid then the force would theoretically be infinite. If they deform (plasticly or elastically) then the force will be less. It'll typically increase gradually as the collision starts, then diminish again. That's why we use soft padding to reduce the forces on things when they're dropped or walked into.

Although it's very complex to model the (changing) force during a collision, we can easily find the overall effect using impulse. I think impulse is what you're looking for. But it's not a force, look it up if you aren't sure.

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#40263 - 09/21/11 03:31 PM Re: Record Cold in New Zealand 1903 -26.6 C [Re: kallog]
paul Offline
Megastar

Registered: 03/21/06
Posts: 4136
if impulse is also not a force then I wont use it either.

1 Newton

is a force of earths gravity on a mass of
about 102 g = (1/9.81 kg) (such as a small apple).

were not discussing anything on earth.

so we shouldnt use newtons as the unit of force either.

1 pound force

is equal to the gravitational force exerted on a mass of one avoirdupois pound on the surface of Earth
so we shouldnt use pound force either.

1 dyne

is the force required to accelerate a mass of one gram at a rate of one centimetre per second squared


maybe we should use dyne as our force because we are not affected by earths gravity in space , in fact lets move the pipe a long distance away from a gravity source so that gravity will not interfere with our discussion.

1 dyn = 1 gcm/s = .00001 N

so 1kg at a velocity of 1000 cm/s = 1000 dyn

so the force for acceleration would be
1000 dyn force = 1 kg at a rate of 10m/s/s
meaning that a force of 1000 dyn applied each second is required to accelerate an 1 kg mass to a acceleration of 10m/s/s

and the impact force would be
1000 dyn = 1 kg at a velocity of 10m/s

the reason I reason the above is because at impact the
product of the impacting objects mass x its velocity is the force that another object will feel. so it does not matter what the impacting objects rate of acceleration was before the impact.

thus my biotch with the current use of the word force only being associated with an accelerating object.

lets call 1000 dyne kdf for killo dyn force

so that we can say things like the following.

1 kdf will accelerate a 1 kg mass to 10 m/s/s
and
a object with a mass of 1 kg and a velocity of 10 m/s strikes a wall with a force of 1 kdf

this way I can use the word force while trying to discuss what were trying to discuss.

as in the force that the mass has as it enters the turn.

that force being the product of its mass x its velocity
and I will use kdf as the units.

or I could do this when communicating.

as in a equation

the product of the masses mass x its velocity = mv

and

a = the product of the masses mass x its velocity / Mass


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

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#40264 - 09/21/11 05:22 PM Re: Record Cold in New Zealand 1903 -26.6 C [Re: paul]
paul Offline
Megastar

Registered: 03/21/06
Posts: 4136
I did find something called a "direct Force" and its definition is below.

http://www.newton.dep.anl.gov/askasci/phy99/phy99x79.htm

Quote:
A direct force is a force between things that are touching. If you take a balloon and bop somebody on the head with it, the force between the balloon and the head is direct.


I found a few more to work with
http://www.newton.dep.anl.gov/askasci/phy00/phy00148.htm
Quote:
What is an easy way for second graders to understand the conceptual difference between momentum and force.

Replies:
Force makes momentum change. Mathematically, the force on an object is equal to the rate at which the object's momentum changes.

Tim Mooney

Not an easy concept to convey to students especially at young age. You might try the following analogy: Acceleration is the rate of change (time) of velocity. This is simple to explain using the concept of acceleration in an automobile. Analogously, force is the rate of change of momentum.

Harold Myron

Force is how hard you push or pull on an object. Momentum relates more to how hard it is to stop an object from moving. A 10mph bowling ball is much more difficult to stop than a 10mph ping-pong ball. The bowling ball has more momentum.

Momentum is within an object, carried with the object. Force is between objects. Momentum is like what the object has in its bank account. Force is like giving some of this momentum to another object every second they are in contact. I use "bank account" rather than "wallet" because a bank account balance can be negative. It allows momentum to have direction.

Kenneth Mellendorf


there is something to this , even in the replies above.

Force makes momentum change
Acceleration is the rate of change (time) of velocity
force is the rate of change of momentum
Force is how hard you push or pull on an object
Momentum relates more to how hard it is to stop an object from moving
--------------------------------------
Momentum relates more to how hard it is to stop an object from moving

what he has said is that momentum is the amount of force
that you need to stop an object.

-------------------
A 10mph bowling ball is much more difficult to stop than a 10mph ping-pong ball. The bowling ball has more momentum.

why didnt he use the word FORCE?
why did he use the word momentum?

could it be that the bowling balls momentum is a force that is the product of the bowling balls mass x its velocity?

notice below where the sentence says 10 mph
it doesnt say 10 mph/h
so he is obviously referring to the product of the
bowling balls mass x its velocity.

A 10mph bowling ball is much more difficult to stop
you would use a force to stop the bowling ball wouldnt you?

and the force he is describing using would be the 10 mph ping pong ball.

notice again the sentence below says 10 mph referring to the ping pong ball.

and he is using the 10 mph ping pong ball as a force obviously!!!

A 10mph bowling ball is much more difficult to stop than a 10mph ping-pong ball.

Force is how hard you push or pull on an object. Momentum relates more to how hard it is to stop an object from moving. A 10mph bowling ball is much more difficult to stop than a 10mph ping-pong ball. The bowling ball has more momentum.

Force is how hard you push or pull on an object

notice above that he says force is how hard you push or pull on an object.

it does not mention distance , speed , acceleration , time , direction , etc ...etc ...etc ...etc ...etc ...etc ...


Momentum is within an object, carried with the object. Force is between objects. Momentum is like what the object has in its bank account. Force is like giving some of this momentum to another object every second they are in contact. I use "bank account" rather than "wallet" because a bank account balance can be negative. It allows momentum to have direction.

Momentum is within an object
carried with the object
Momentum is like what the object has in its bank account
I use "bank account" rather than "wallet" because a bank account balance can be negative. It allows momentum to have direction.


Force is between objects
Force is like giving some of this momentum to another object every second they are in contact.


Momentum is within an object
carried with the object
Momentum is like what the object has in its bank account

I would have to say that what is has in its bank account is force.

after reflection on this matter I believe we dont need to use a different word , we only need to redefine the meanings of the words we already use.

and I would have to say that
p=mv
means
the force of momentum = mv

and I can say things like

the momentum force of the 100 kg mass that enters the turn
at a velocity of 40 m/s = 4000 kg m/s

it only makes sence because that is the amount of force that the turn would feel if the 100 kg mass were to collide with the turn at a velocity of 40 m/s during a time of 1 second.

100 kg x 40 m/s( applied in one second ) = 4000 kg m/s/s = 40N force

Quote:
then tell me what is a unit of momentum.
unit kgm/s, or, equivalently, Ns


the turn does not know the rate of acceleration that the 100 kg mass was being accelerated at.

and the mass is no longer being accelerated as it enters the turn.

as a mass gains velocity its momentum increases so it can build up a great amount of momentum , and by doing so a great amount of momentum force is also built up.

so the mass hits the turn with all the force it has in its momentum account.

f=ma

what does the above really mean?
break it down

f = force
m = mass
a = acceleration

the 100 kg mass has an acceleration of 0.8 m/s/s

if we only use the mass x the rate of acceleration of the mass to calculate the impact force of the collision we get

f=ma
force N = 100 kg x 0.8 m/s/s
80N

but if we only use the mass x the velocity of the mass to calculate the impact force of the collision we get

f=mv
force N = 100 kg x 40 m/s (applied for 1 second)
4000N

we may need to re-invent a physics math that makes sence.

f=mvt

force = mass x velocity x time

like the pipe

applying a 4000N force for 50 seconds

f=mvt=200000N
and applying that force in the positive direction
f=m(+v)t=+200000N
or
f=m(-v)t=-200000N

so much simpler.

and gives the same result.

then we could do a one liner such as

f=(m1(v1)t1)+(m2(v2)t2)

where

m1 = 200kg
v1 = 40 m/s
t1 = 50 seconds
m2 = 1000 kg
v2 = 4 m/s
t2 = 50 seconds

f=(+400000N ) + (-200000N)
f=+200000N


or we could just use one of your springs to travel to other galaxies with.

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

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#40267 - 09/21/11 05:37 PM Re: Record Cold in New Zealand 1903 -26.6 C [Re: paul]
Bill S. Offline
Megastar

Registered: 08/20/10
Posts: 3570
Loc: Essex, UK
If, instead of bopping the person, you let the air out of the balloon, such that the person feels the force of the air on her/his face, is that still a direct force?
_________________________
There never was nothing.

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#40268 - 09/21/11 06:08 PM Re: Record Cold in New Zealand 1903 -26.6 C [Re: Bill S.]
paul Offline
Megastar

Registered: 03/21/06
Posts: 4136
youll have to ask kallog about that , I no longer understand what a force is , or how to communicate things that should have a force associated with it due to its movement.
_________________________
3/4 inch of dust build up on the moon in 4.527 billion years,LOL and QM is fantasy science.

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#40272 - 09/22/11 12:57 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

maybe we should use dyne as our force because we are not affected by earths gravity in space , in fact lets move the

The SI definition of the newton is exactly what you want -
"the force required to accelerate a mass of one kilogram at a rate of one meter per second squared".


Quote:

the reason I reason the above is because at impact the
product of the impacting objects mass x its velocity is the force that another object will feel. so it does not matter

How many times do I have to tell you that acceleration is not the same a velocity? The product of a mass and a velocity is not a force! To experience a net force it must accelerate, and it must accelerate at the same time as the force is being applied, not immediately beforehand.

What this means is the force depends on how quickly the object slows down when it hits something. That's the acceleration you can use to determine the force by F=ma. But it's also difficult to calculate, and it varies with time - as I've mentioned before.




Quote:

what the impacting objects rate of acceleration was before the impact.

Not relevant to the force of the impact.


Quote:

a object with a mass of 1 kg and a velocity of 10 m/s strikes a wall with a force of 1 kdf

Most of the time that will be wrong. If you put a force meter on the wall, you'll find the force is usually not 1kdf. Did you completely ignore my last message? The force of the impact depends on the deformation of the objects - ie the materials they're made from.

Quote:

this way I can use the word force while trying to discuss what were trying to discuss.

What you call "force" above is effectively "impulse" (apart from the wrong units). If you want to use it, call it impulse because it's not a force. And use the correct units. Multiplying kg by m/s always gives kg.m/s, which is a unit of impulse.


Quote:

the product of the masses mass x its velocity = mv

That's it's momentum. If you're talking about the collision, and v is the relative velocity immediately before, and the object stops, then it's the impulse. I'm pretty sure you mean impulse.


Quote:

a = the product of the masses mass x its velocity / Mass

That's a velocity, not an acceleration. Calling it "a" will be endlessly confusing. Call it v or v_mass or whatever distinguishes it from other velocities.

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#40273 - 09/22/11 01:11 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

the 100 kg mass has an acceleration of 0.8 m/s/s

if we only use the mass x the rate of acceleration of the mass to calculate the impact force of the collision we get

f=ma
force N = 100 kg x 0.8 m/s/s
80N

That's correct, as long as it's accelerating at 0.8m/s^2 _during the collision_. However it's not necessarily doing that in our pipe.




Paul, you have to include units in calculations, otherwise the results are automatically wrong no matter what names you call things. Eg:

2kg * 5s = 10kg.s.
It can never equal 10 kg.m or 10 N/foot or anything which isn't equal to 10 kg.s.

2 jabdabs * 5 yibyobs = 10 jabdab yibyobs.

2kg * 5m/s = 10 kg.m/s.
It can never equal 10 kg.m/s/s or 10N or 10dynes or anything that isn't equal to 10kgm/s. It does however equal 10Ns because 1Ns = 1 kgm/s.



Edited by kallog (09/22/11 01:16 AM)

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#40274 - 09/22/11 04:32 AM Re: Record Cold in New Zealand 1903 -26.6 C [Re: kallog]
paul Offline
Megastar

Registered: 03/21/06
Posts: 4136
Quote:
Force is not momentum. Velocity is not acceleration. Let's find its momentum after 2 seconds:
p=mv
p=ma*t
1000000 x .00004 x 2 = 80Ns

Let's find its momentum after 1000 seconds:
p=mv
p=ma*t
1000000 x .00004 x 1000 = 40,000Ns


how long is the spring your using kallog?

because even if its 1000000 km long and you only compress it to 40N , 40N is all you can get out of it.

its just like compressing air into a air cylinder.

so when you say 1000 seconds it must be pretty long because its acceleration is only .00004 m/s/s

from what I can tell its 20 meters long.

if you applied a force of 40N over a distance of 20 meters to compress the spring.

or if you compress the spring in only 1 second using a force of 40N

then you can only get 40N out of it no matter how long it takes for the spring to expand.

so the spring expanded for a distance of 20 meters and then the solar sail just free floats.

because the spring is only 20 meters long.

so how did you end up with 40000N?

is it because the spring requires more force than 40N to compress?

perhaps it requires 40N per second if you compress it for 1000 seconds.

the above is why we shouldnt use momentum.

from now on I will use push and pull

to avoid the things that just dont make any sence to me.

a 40 kg push
a 40 kg / sec push

a 40 kg pull
a 40 kg / sec pull

replacing the word force with the word push or pull

so that I can say something like the following.

the 10 kg mass hit the wall at a velocity of 2 m/s with a push of 20 kg m/s.

the mass has a push of 50 kg m/s

the mass is accelerated to a velocity of 10 m/s/s
by a push of 500 kg m/s

push = mass x acceleration

500P = 50 kg x 10 m/s/s

push and pull replacing both force and momentum.



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

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#40275 - 09/22/11 05:27 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

because even if its 1000000 km long and you only compress it to 40N , 40N is all you can get out of it.

Yes but that doesn't stop it gaining a lot of momentum (and speed). We must be talking about different things. In my world if you push something frictionless, it accelerates. And it keeps on accelerating as long as you keep pushing it. It doesn't matter if you're wearing spongey gloves or you're holding a spring, you still push it, and it still keeps getting faster and faster as long as you keep pushing it.


Here I've replaced your "push" with the conventional words having the same meaning:


the 10 kg mass hit the wall at a velocity of 2 m/s with a push/impulse of 20 kg m/s.

the mass has a push/momentum of 50 kg m/s

the mass is accelerated to a velocity of 10 m/s/s
by a push/impulse of 500 kg m/s

push/force = mass x acceleration

500P/N = 50 kg x 10 m/s/s

push and pull replacing both force and momentum inconsistently.

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#40282 - 09/22/11 05:58 PM Re: Record Cold in New Zealand 1903 -26.6 C [Re: kallog]
paul Offline
Megastar

Registered: 03/21/06
Posts: 4136
OK, momentum is not a force.
impulse is not a force either.
the only thing that is a force is a force of course.

so after each 100 kg mass has been accelerated for 1000 meters at a rate of acceleration of .8 m/s/s and has reached a velocity of 40 m/s during a time of 50 seconds.

the following is true after each mass has traveled 1000 meters just before it enters the turn.

each 100 kg mass has a momentum of
p=mv
-4000 Ns = 100 kg x -40 m/s

and

each 100 kg mass has a force that it can apply to an object of
f=ma
-80N=100 kg x -.8 m/s/s

because momentum is not a force it cannot push an object.

so the only force that can push against the pipe in the (-)
direction is the force that is the product of the 100 kg mass
times its acceleration.
which is -80N

correct?


Quote:
the 100 kg mass has an acceleration of 0.8 m/s/s

if we only use the mass x the rate of acceleration of the mass to calculate the impact force of the collision we get

f=ma
force N = 100 kg x 0.8 m/s/s
80N


That's correct, as long as it's accelerating at 0.8m/s^2 _during the collision_. However it's not necessarily doing that in our pipe.


That's correct

Quote:
as long as it's accelerating at 0.8m/s^2 _during the collision


as the mass passes through the turn at 40 m/s it undergoes a constant acceleration , it maintains this constant acceleration through the turn because it maintains a constant angular velocity.
the reason it maintains a constant acceleration is because it must be accelerated towards the center of the turn as it passes through the turn , this acceleration is called angular acceleration.


The product of a mass and a velocity is not a force!

How many times do I have to tell you that acceleration is not the same a velocity?


that would be a force of 40N.s

Ararrh13!#@ Force does not have units of Ns!!!! That's momentum.

What is an easy way for second graders to understand the conceptual difference between momentum and force.

Replies:
Force makes momentum change. Mathematically, the force on an object is equal to the rate at which the object's momentum changes.

Tim Mooney

Not an easy concept to convey to students especially at young age. You might try the following analogy: Acceleration is the rate of change (time) of velocity. This is simple to explain using the concept of acceleration in an automobile. Analogously, force is the rate of change of momentum.

Harold Myron

Force is how hard you push or pull on an object. Momentum relates more to how hard it is to stop an object from moving. A 10mph bowling ball is much more difficult to stop than a 10mph ping-pong ball. The bowling ball has more momentum.

Momentum is within an object, carried with the object. Force is between objects. Momentum is like what the object has in its bank account. Force is like giving some of this momentum to another object every second they are in contact. I use "bank account" rather than "wallet" because a bank account balance can be negative. It allows momentum to have direction.

Kenneth Mellendorf



since the 100 kg mass does not loose any of its velocity as it travels through the turn then it hasnt given any of its momentum to the pipe.

because it still has its mass and it has 40 m/s velocity
only in a new direction.
but mostly because its momentum cannot push the pipe with force because momentum is not a force.

p=mv
+4000Ns = 100 kg x +40 m/s

all it has done is gone through a turn.

the only force that could cause the pipe to reduce its acceleration is the force available from the 100 kg mass.

and the 100 kg mass only has a -80N force as it enters the turn and collides with the pipe

however there are 100 masses supplying a +80N force to the pipe while they are accelerating and decelerating durring the 1 second that the 100 kg mass is applying its -80N force.

thats +8000N vs -80N




there will be a force felt by the turn as the mass passes through the turn and that force is the centripetal force
which is a force that is directed towards the center of the turn.
Quote:
Centripetal force (from Latin centrum "center" and petere "to seek") is a force that makes a body follow a curved path


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

fc=mv^2/r
the radius of the turn is 12.73 meters

fc = 100 kg x (40 m/s * 40 m/s)/r
fc = 100 kg x 1600 / r
fc = 160000 /12.73
fc = 12568N

but that force is not an outward force that would cause the
pipe to decelerate.

then there is the fictitious centrifugal force that is supposed to be an outward force.

however since it is a fictitious force we will not concern ourselves with it.

there is one thing to consider also , as the mass passes through the middle of the turn its velocity is directed at a 90 degree angle from the center of the turn as in the below illustration.



so as the mass passes through any part of the turn the -80N force that it can use to push the pipe with in the (-) direction is always at a 90 degree angle to the center of the turn and only momentarily toward the (-) direction as it first enters the turn.

the mass that is passing through the turn is undergoing centripetal acceleration , this acceleration is toward the center of the turn , not away from the center of the turn.

ac = (v^2)/r
ac = (40 m/s x 40 m/s)/12.73
ac = 125.678 m/s/s

the mass accelerating towards the center of the turn at a acceleration of 125.678 m/s/s times it mass = its force.
f=ma
f=100 kg x 125.679 m/s/s = 12567.8N

seems that that was the centripetal force ?

yes , it was..
here it is again.
fc=mv^2/r
fc = 100 kg x (40 m/s * 40 m/s)/r
fc = 100 kg x 1600 / r
fc = 160000 /12.73
fc = 12568N

and all thats left is friction.

















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

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#40288 - 09/23/11 01:13 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
each 100 kg mass has a force that it can apply to an object of
f=ma
-80N=100 kg x -.8 m/s/s

That -80N is the force applied by the accelerator to cause the -0.8m/s^2 acceleration.


Quote:

so the only force that can push against the pipe in the (-)
direction is the force that is the product of the 100 kg mass
times its acceleration.
which is -80N

correct?

No, that's the force pushing against the mass while it's accelerating.




Quote:
[accelerated towards the center of the turn as it passes through the turn , this acceleration is called angular acceleration.

The direction from the mass to the center obviously changes depending on the position of the mass in the turn, so the direction of the acceleration changes, so the acceleration isn't constant.

In half-circle turn, the acceleration can't be constant for that reason, but we can always make the "turn" using some mechanism that applies a constant force and causes a constant acceleration.



Quote:

since the 100 kg mass does not loose any of its velocity as it travels

Its velocity changes at it travels through the turn. Its speed does not. The change in velocity means it must transfer momentum with the pipe.

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#40289 - 09/23/11 01:22 AM Re: Record Cold in New Zealand 1903 -26.6 C [Re: kallog]
paul Offline
Megastar

Registered: 03/21/06
Posts: 4136
Quote:
That -80N is the force applied by the accelerator to cause the -0.8m/s^2 acceleration.


well then , OK.
so there is no force that the mass can apply to the turn as the mass enters the turn.

because the mass is no longer accelerating as it enters the turn.

it just slips into a hole.
it doesnt really have any weight because there is very little
gravity in space.

but there would be some friction as the mass presses against the turn going through the turn.

we already know that momentum is not a force and a force is required to push an object.

the mass does have momentum , but momentum is not force.

I have covered the centripetal force.
which is not a outward force.


and the centripetal acceleration.
which is not a outward acceleration.



Quote:
the mass that is passing through the turn is undergoing centripetal acceleration , this acceleration is toward the center of the turn , not away from the center of the turn.


centripetal acceleration is constant acceleration btw.
because the mass is constantly accelerating towards the center.

the centripetal force (center seeking ) = fc = 12568N

so where does this leave us?

heres a good calculator
http://www.calculatoredge.com/new/centripetal.htm#velocity

Quote:
Its velocity changes as it travels through the turn. Its speed does not. The change in velocity means it must transfer momentum with the pipe.


all of the below is in the same context.
--------------------------------------------
since the 100 kg mass does not loose any of its velocity as it travels through the turn then it hasnt given any of its momentum to the pipe.

because it still has its mass and it has 40 m/s velocity
only in a new direction
.
--------------------------------------------

Quote:
transfer momentum with the pipe


how is that accomplished?





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

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#40293 - 09/23/11 04:50 AM Re: Record Cold in New Zealand 1903 -26.6 C [Re: paul]
kallog Offline
Megastar

Registered: 03/17/10
Posts: 1100
Key points:
- Velocity includes both speed and direction.
- Acceleration occurs if either or both parts of velocity change.
- Acceleration requires a force.



Originally Posted By: paul

so there is no force that the mass can apply to the turn as the mass enters the turn.

because the mass is no longer accelerating as it enters the turn.

It is accelerating in the turn. And therefore it is applying a force to the pipe.

We know it's accelerating because its velocity is changing.

As you surely know, velocity includes speed and direction. If any part of the velocity changes then it's accelerating. Obviously direction is changing, therefore it's accelerating, therefore it's applying a force to the pipe.




Quote:

centripetal acceleration is constant acceleration btw.
because the mass is constantly accelerating towards the center.

"towards the center" only sounds like a constant direction because of English. Obviously the direction of the center keeps changing. So the direction of the acceleration is also changing.




Quote:

since the 100 kg mass does not loose any of its velocity as it travels through the turn then it hasnt given any of its momentum to the pipe.

Its velocity does change. So it does transfer momentum with the pipe.

Quote:
only in a new direction

Exactly! The change of means the velocity is changing. That's because direction is part of velocity.


Note: I use the word "obviously" to show that an idea can easily be seen from common sense. If you can't see it then you must be looking for the wrong thing. In other words, if it's not obvious to you, then you're probably overthinking it or misunderstanding me.

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#40303 - 09/23/11 02:31 PM Re: Record Cold in New Zealand 1903 -26.6 C [Re: kallog]
paul Offline
Megastar

Registered: 03/21/06
Posts: 4136
Quote:
It is accelerating in the turn.


what force from what object is being used to cause its momentum to change that causes it to accelerate?

it cant supply the force to change its momentum so it cant change its velocity itself so it cant accelerate itself.

wasnt it newton who said that an object will remain in a straight line unless a external force is applied to change its direction.

Quote:
We know it's accelerating because its velocity is changing.


as far as I can tell we havent agreed on a force that will cause its velocity to change , therefore we dont know that its accelerating.

Quote:
As you surely know, velocity includes speed and direction. If any part of the velocity changes then it's accelerating. Obviously direction is changing, therefore it's accelerating, therefore it's applying a force to the pipe.


in order for the mass to change velocity there must be a external force that is applied to to the mass to cause the mass to change its direction.

so , where does this force come from and what amount of force is it , and in which direction is it comming from?

you say the mass is applying a force to the pipe.
but the mass only has momentum , and momentum is not a force.

the pipe has a force because of its mass x its acceleration
f=ma
1000kg x 8 m/s/s = 8000N
the 8000N is a force that can apply itself to the mass.

but the mass does not have a force that it can apply to the pipe , it only has momentum.

p=mv
4000Ns = 100kg x 40 m/s
the 4000Ns momentum is not a force that can apply itself to the pipe.

so where is this force that you are speaking of comming from?

the mass
or
the pipe

the mass has no force it can apply.
so wouldnt it be the pipe because it has a force?

Quote:
"towards the center" only sounds like a constant direction because of English. Obviously the direction of the center keeps changing. So the direction of the acceleration is also changing.


the centripetal force is in a constant direction.
and that direction is towards the center.
the direction of the force never changes it is always towards the center.
so the direction of the acceleration is always towards the center.
when the mass changes its direction it changes it towards the center.

when the mass changes its direction towards the center it is accelerated towards the center.

so the change in direction and the centripetal acceleration is always towards the center.

Quote:
Its velocity does change. So it does transfer momentum with the pipe.


we dont know that yet , we havent agreed on what would cause its velocity to change.
some force has got to be applied to the mass to make it change its velocity.

so wheres the force?

Quote:
Exactly! The change of means the velocity is changing


velocity is not a force.

Quote:
That's because direction is part of velocity.


direction is not a force.

and mass is not a force.

so where is the force?

Quote:
Note: I use the word "obviously" to show that an idea can easily be seen from common sense.


is that a theory you have?

common sence has nothing to do with math.

Quote:
If you can't see it then you must be looking for the wrong thing. In other words, if it's not obvious to you, then you're probably overthinking it or misunderstanding me.


in math you need elements to include in equations.

you cant just use your common sence in an equation.

it does not matter if something is obvious or not.

common sense and thinking can not be used to cause a mass to have a change in momentum or velocity or direction or acceleration.

but a applied force can , wheres the force?

heres a pretty good definition of force
http://en.wikipedia.org/wiki/Force
Quote:
In physics, a force is any influence that causes an object to undergo a change in speed, a change in direction, or a change in shape. Force can also be described by intuitive concepts such as a push or pull that can cause an object with mass to change its velocity (which includes to begin moving from a state of rest), i.e., to accelerate, or which can cause a flexible object to deform. A force has both magnitude and direction, making it a vector quantity. Newton's second law, F=ma, was originally formulated in slightly different, but equivalent terms: the original version states that the net force acting upon an object is equal to the rate at which its momentum changes.


so from what I can see what we have is the following.

the force and momentum associated with the pipe that will be involved in the collision.

note: the pipe would normaly have an acceleration of
8 m/s/s because there are 100 100kg masses being accelerated and decelerated every second and the force that accelerates and decelerates the 100 masses
is f=ma = (100 masses x 100 kg) x .8 m/s/s = 8000N

so the force that the pipe could normaly apply to an object would be 8000N after 101 seconds.

so the pipe would normaly have a momentum of

p=mv = 1000 kg x +80 m/s = +8000Ns

but thats not what we have because there is a
single 100 kg mass going through the turn each second.

the force and momentum associated with the 100 kg mass that will be involved in the collision.


mass momentum = p=mv = 100 kg x -40 m/s = -4000Ns

mass force = f=ma =100 kg x .8 m/s/s = 80N










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

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