A problem with KE = ½mv². Help.

[Farsight]

We also know that each time you raise an object double its previous height, it doubles its velocity leading to x4 of the energy

 

The bold bit. An falling object will reach 9.8m/s after one second, and 19.8m/s after two seconds. But it falls further in the second second.

 

I'll have to get back to you later on the summary stuff, arkain. After I've had time to mull it over.

[CraigD]

Which part is not correct?

 

1)An object dropped from hieght A will impact at certain velocity, and the same object dropped from twice the height of A will impact at twice the velocity

This statement is incorrect. An object dropped from twice the height of A will impact at 2^.5 (about 1.414) times the velocity as one dropped from a height of A.

an object that doubles its velocity, gains 4x the energy than it previously had (at half the Vfinal).

This statement is correct.

[arkain101]

Please take the time to read this particular post, I present here some very interesting claims. I know how some long posts just get jumped over, but, take time to read into this.

This statement is incorrect. An object dropped from twice the height of A will impact at 2^.5 (about 1.414) times the velocity as one dropped from a height of A.

 

Okay, so the PBS program, 'NOVA' lied to me lol...So that is established, good.

 

Moving on to the rest.

 

"An object that doubles its velocity, gains 4x the energy than it previously had at half the Vfinal".

 

When we look at why this is, our answer is;

All actions have an equal and opposite reaction. An action is a interaction between two or more objects.

 

So, if you double the velocity of an object (double its momentum), the second object it collides with will respond with an equal opposite reaction, thus causing an energy capability equal to 4 times the previous measurement at half the current (Vfinal) velocity.

 

Then we look at why exactly all actions have an equal and opposite reaction. This is explained by objects having inertia. The term inertia is used to explain the tendency of an object at rest to remain at rest, and of an object in motion to remain in motion.

 

Leading into Inertia.

Why do objects have this tendency to remain in their current state that we call Inertia, that creates the equal and opposite reaction of all actions?

 

We look at objects,

All objects have a value. The combination of many single values creates the mass value of the object. So we can look at objects as nothing more than values. And these values work in a consistent mathamatical system, they remain steadfast in the laws that govern the universe.

 

Now we look at all this in action, with this EXAMPLE.

 

In this exampe we have TWO seperate lone objects in a universe. We call them object 1 and object 2. Lets make them each a copy of the moon that orbits our earth.

The two moons are the only objects one can see in this universe. (if you want to be picky, we can say they are the only two objects close to eachother with empty space millions of light years in size surrounding them.)

We call the moon 1 (object 1) and moon 2 (object 2).

The two objects are measured to be moving towards eachother. An observer on object 1 measures that object 2 is coming towards them at 100m/s.

(we ignore gravity)

An observer on object 2 measures that object 1 is coming towards them at 100m/s.

Each person measures and records the correct and accurate data.

So either one can be assumed to be moving, there is no other reference frame in which to compare to.

 

 

part I:

 

We are going to say that object 1 is at rest and object 2 is in motion (they both have the same mass).

 

The Kinetic energy is going to be equal to

'mass of object 2' * Velocity^2 of object 2, all devided by 2 (1/2).

 

If the object 2 was traveling at half the current velocity the energy would be 1/4 of the current amount, and if object 2 was traveling 2x the current velocity (current velocity is 100m/s) then energy would be 4x the current amount.

 

When object 2 hits object 1, a number of details are involved.

 

-object 2 will stop and the momentum will be conserved sending object 1 off at 100m/s.

-EACH object will experience the same force

-The energy measured will be due to the law of all actions having equal and opposite reactions.

-the forces, energy, and momentum will function because of what is called the inertia of the objects.

 

Part 2:

Now, we take the point of view of observer 2's posistion, on object 2. Now we have object 2 considered at rest and object 1 in motion. All the values remain the same, but the actions are opposite.

 

In this particular EXAMPLE, each observer is 100% correct in their observations.

 

The inertia of either object when considered at rest while the other is in motion is equal to the mass value of the either object in motion while the other is at rest.

 

thus, in two object interaction scenarios,

 

Inertia of an object at rest, when the object of reference is in motion, is the act of same thing happening from the other observation frame that is occuring in the one of reference.

And,

The momentum/motion-inertia of the other object, when the object of reference is a rest, is the act of the same thing happening in the other observation frame that is occuring in the one of reference.

Just like two observations of the example above.

 

In our consciousness, we can not have both happening at the same time because it thus states each object is moving. But in mathamatical terms, it can be written as,

Actions of object 1 = actions of object 2

 

Thus all detials of these interactions can be derived back and forth among this equation.

 

It is not important which object is in motion in an action. The events just simply transpire in a mathamatical order. The very two objects (in an example) do not even have to be real, the mathamatical order is what is operating the event.

 

By real I mean,

whether you can actually see the parts that make up the matter or not is not important, they could actually not be there in a tangible sense, but instead, they are starting points in a mathamatical system, and where the starting points come from the values and constants of nature that work in the mathamatical system that operates what we interpret as the nature of the universe.

 

Space-time is like this mathamatical system. It is not something we can directly think of, it is not somthing we can grab onto with our hand and manipulate (its not seperate from anything you try to show it with, so you only show what shows it). When you try to show it, the closest and best way is through geometric and mathamatical operations which make use of other dimensional equations to add to the representation of space-time. But these other dimensions and geometry visuals are yet more mathamatics, and are not part of what our mind can visualize or imagine.

So if we choose to accept that matter and energy are alike space-time, and are not tangible fabrics in the matter sense, but are more like mathamatical operations which can be mathamaticaly represented, then we begin closing up the loops in physics, IMO.

 

When you really think about it, all the forces of nature are things we cannot see directly(gravity, nuclear forces, magnetism), yet they are very real. While all the things we can see are what we call matter and energy.

But why do we think these are so real?

When matter-energy are compared to the rest of the universe, in terms of how we exist, see, imagine, and interact with them, matter and energy are actually alot more. not real, more,very supernatural, when we refer Matter-energy visual tangible type things and mathamatical invisible forces are put in direct comparison of eachother.

[Farsight]

Yes arkain. IMHO the whole reason for this thread is that Kinetic Energy is not in fact "real". It's relative, and an abstraction, a concept for mass and motion. But "real" is a slippery thing. Take your consciousness. It has no shape, no colour, no size, no charge, no spin, no velocity, no mass. And since it's merely a figment of your imagination, I therefore conclude that it is not real.

 

But please let's not get into philosophy. Let's stay on the topic of Kinetic Energy.

 

If Momentum is the same as Inertia, and Impulse, which is Force x Time, and if Kinetic Energy is Force x Distance, is there a deep concept available here? Is Distance the same as Space? Is Mass the same as Inertia? And is the relationship between "Mass" and "Energy" a re-expression of the relationship between time and space?

[arkain101]

I agree, lets not get philisophical, but for thoughts on the side, is it not intriguing thinking that everything we see and experience is a little more supernatural than all the laws, physics, and mathamatics of nature?

[CraigD]

If Momentum is the same as Inertia, and Impulse, which is Force x Time, and if Kinetic Energy is Force x Distance, is there a deep concept available here? Is Distance the same as Space? Is Mass the same as Inertia? And is the relationship between "Mass" and "Energy" a re-expression of the relationship between time and space?

There is a deep connection between mass and kinetic energy. Its formulation includes a well known and what is likely the most popularly well known equation in modern physics:

Mass = Massrest/(1 – (Speed/Speedlight)^2)^.5

Energy = Mass * Speedlight^2

(better known as e=mc^2)

 

Consider the alternative calculation of the kinetic energy of a 0.2 kg puck accelerated to 50 m/s:

Massrest = 0.2 kg

Energyrest = 0.2 kg * (299792458 m/s)^2 = 17975103574736352.8 J

Mass = 0.2/(1 – (50/299792458)^2)^.5 = ~ 0.2000000000000027816 kg

Energy = 0.2000000000000027816 * (299792458 m/s)^2 = 17975103574736602.8

 

The puck gained kinetic energy of

Energy - Energyrest = ~ 17975103574736602.8 - 17975103574736352.8 = ~ 250 J

, as given the classical equation e = (1/2)mv^2 !

 

Note that this amazing coincidence is only approximate (which I usually indicate with the “~” symbol). If I were using a calculator with higher precision, a small discrepancy in the classical and modern calculated energy value would appear. Also, if the velocity is much (say, a million times) higher, the modern calculation gives:

Mass = 0.2/(1 – (50000000/299792458)^2)^.5 = ~ .2400332343100607145 kg

Energy - Energyrest = ~ 21573111240511504.6 - 17975103574736352.8 = 3598007665775151.8 J

, while the classical one gives: 250000000000000 J, a 3348007665775151.8 J (7%) discrepancy.

 

If we increase the velocity by another factor of 100, to a speed greater than that of light, the modern calculation are no longer usable, giving a result that is a complex (imaginary), not real, number.

 

Which calculation, the modern or classical, is more correct? The modern. In light of modern (AKA relativistic) physics, classical mechanics should be considered useful approximations, to be used only when velocities are a small fraction of the speed of light, and slightly inaccurate results are acceptable.

 

In terms of absolute reality, even the relativistic calculations are slightly incorrect, which brings us to Arkain’s observations about forces and reality…

When you really think about it, all the forces of nature are things we cannot see directly(gravity, nuclear forces, magnetism), yet they are very real. While all the things we can see are what we call matter and energy.

But why do we think these are so real?

When matter-energy are compared to the rest of the universe, in terms of how we exist, see, imagine, and interact with them, matter and energy are actually alot more. not real, more,very supernatural, when we refer Matter-energy visual tangible type things and mathamatical invisible forces are put in direct comparison of eachother.

I wouldn’t chose the term “supernatural” to describe the fundamental forces, though “weird” seems a good one, especially in the phrase “quantum weirdness”. “Amazing”, “awe-inspiring”, “fascinating”, “wonderful” also come to mind when I consider the emotions I associate with studying Physics.

 

According to the best accepted theory, the interactions responsible for mechanical phenomena like we’ve been discussing in this thread is predominantly the exchange of photons by electrons and electrons and electrons and quarks. For example, the part where the puck-pushing part of the spring gun accelerates the puck following approximately this scenario:

1. • An electron A in an atom in the spring gun emits a photon B, and a photon C
     
   • A’s energy is reduced by the energy of B and C.
     
   • Quark(s) D in the nucleus of A’s atom emit photon(s) E
     
   • An electron F in an atom in the spring gun emits a photon G, and a photon H
     
   • F’s energy is reduced by the energy of G and H.
     
   • Quark(s) I in the nucleus of F’s atom emit photon(s) J
     

[*]

• A absorbs E and G
  
• D absorbs C
  
• F absorbs B and J
  
• I absorbs H
  

This is repeated many, many times, ultimately resulting in the transfer of energy and momentum between the ensembles of atoms in the puck and the spring gun.

 

I’ve described the interaction between the fundamental particles as if they were classical, certain events, so, while complex and difficult to precisely calculate, they aren’t yet “weird”. Where the “quantum weirdness” enters the description is when we consider that, according to quantum mechanics, electrons, photons, and quarks are not particles with definite positions and velocities, but mathematical functions that can be used to calculate the probability of each particle being at a specific location with a specific velocity.

 

This probabilistic interpretation of the (very difficult!) mathematical formalism of quantum mechanics means that, even when we use modern, relativistic calculations, our results describe only the most likely event, not the event that will actually be observed. For experiments involving sleds and pucks, where the number of particle interactions are on the order or 10^30, the probability that the observed event will differ significantly from the calculated one is so small it can be ignored. There is, however, a miniscule but non-zero probability that the event will be something very different than we predicted, completely violating the relativistic versions of the laws of conservation of momentum and energy, and even the more basic laws of motion and geometry!

 

Very weird, and very wonderful!

[Farsight]

Thanks Craig.

[arkain101]

I wouldn’t chose the term “supernatural” to describe the fundamental forces, though “weird” seems a good one, especially in the phrase “quantum weirdness”. “Amazing”, “awe-inspiring”, “fascinating”, “wonderful” also come to mind when I consider the emotions I associate with studying Physics.

 

I meant to apply those descriptions towards the things WE see, WE feel, etc. There is a whole load of things to this reality. It seems everything so far has been able to be classified through mathamatics/physics and this is where I tried to describe everything of action (like mass and light, and senses) more on the supernatural side of things than the mathamatical operation of the universe (which includes light 'speed', quantized operation, constant nuclear forces, gravity).

 

So I wonder to suggest; that what gives things "mass" is not fabric of sorts type concept (a materialism of kind seems more supernatural), instead what gives mass, mass is the equation I suggest CAN be formed.

 

In the equation it says nothing is real, in a fabric like sense, but the mass and inertia of matter and energy is due to a programmed equation and mathamatical control, as like the rest of the universe appears to be under.

 

Something tells me we need to look at this idea an important consideration for the progres of undestanding.

 

I wonder that everything in the universe is a controlled like design, and our part here, and all we as life can experience is the supernatural core, and the reason for the mathamatical controlled not tangible universe.

[Farsight]

The Universe isn't defined by mathematics, arkain. Mathematics is just a way of writing down how the things that make up The Universe hang together. Sure, some of the things we take for granted don't "really" exist. But they do too, only they aren't what we think they are. It's like if you were made out of magnetic field, a magnet's repulsion would feel like something solid. Do try to work harder to grasp the concepts here, don't give up and turn to the "supernatural". And even if The Universe was designed, that would mean you'd have that curiosity and wonder for a reason.

[arkain101]

The Universe isn't defined by mathematics, arkain. Mathematics is just a way of writing down how the things that make up The Universe hang together.

 

No worries of where I posistion myself in beliefs, you assumed and that just causes problems.

 

My thoughts expressed here are nothing more than suggestions. If we accept things this way, this here makes sense. Then we can understand this, and if that is accepted than this concept here unites with the first.

 

I did not mention it was suggestive and I havnt shown how if accepted what it shows. I am working with that when the time allows me to.

 

Remember how strange relativity can be.Mathamatics could be made because of the universe, or the universe could work because mathatics operates it, depending on where you observe from.

sort of like;

Math is equal to universe. M = U

And/or its equally,

Universe is equal to math U = M

 

before I posted this I did some writing of an equation and using what craig had shown Mass = Massrest/(1 – (Speed/Speedlight)^2)^.5 I think I can begine to show a new equation.

 

I was just reading a section in WIKI about einstien and how his theory was developed. There was things I hadnt known about how he developed his theory and as I read through I realised I have been unknowling developing the same theory with one difference. This one difference could show or help to show how to connect quantised action with relativistic operation. Then as einstien also found, gravitiy needed to be re-defined. Likewise I found it to need to end up like einstien found, yet with a tweak of detail.

 

I shouldnt get ahead of myself. I dont mean to try and sound like einstien, but I work with passion and get goin when I see progress occuring.

 

This part was cool to read.

Relativity:

While this revolutionary theory did significantly change the meaning of many Newtonian concepts such as mass, energy, and distance, Einstein's concept of inertia remained unchanged from Newton's original meaning (in fact the entire theory was based on Newton's definition of inertia).

 

Mainly what I have been doing here, yet taking it one step further I hope.

[arkain101]

Okay this is what I have developed so far, and would like any help I could get from some more experts.

 

Trying to explain the theory postulates best as possible.

 

1)A) Joining relativity to quantum aciton

 

Inertial mass (and MASS alone) is the action of quantized action in relativistic view.

I tried with an equation but am having difficulty.

 

Equation written for 2 Objects of matter (that can be measured to have inertial mass) the two objects are M1 (object 1) and M2 (object 2). 1 velocity measured from each observing point/frame.

 

M1v= mass 1 at velocity(value)

M1r= mass 1 at rest

M2v= mass 2 at velocity

M2r= mass 2 a rest.

 

Spoken as. Mass 1 at velocity (#) + Mass 1 at rest measurement velocity (0) (exclude mass value, its only for show for operating the equation from the 2nd possible reference frame) is the same as or equal to, Mass 2 at velocity (#) and M2 rest velocity.

 

M1v + M1r = M2v + M2r

 

Written like this observing from Object 2 (so it looks at rest)

M1(10m/s velocity) + M1(0rest) = M2(0velocity) + M2(10m/s rest)

 

Written like this observing from Object 1 (so it looks at rest)

M1(0 velocity) + M1(10m/s rest) = M2(10m/s velocity) + M2(0rest)

 

A mass in velocity colliding with another mass at rest, is the same situation vice versa at the same time. This makes the object at rest have inertia at rest, and the object in motion have inertia in motion for each relative observing point.Our relative view sees only one object moving.

 

In the above equation both objects are moving in the equation but cant be measured from one observation point. When the velocity increases of one object from the view of one observation frame the same thing happens to the other object in another observation frame, this causes the quanitfied action of motion.

 

The quantified action of matter/motion is that, every action has an equal and opposite reaction of things you can see or can not. This makes a measureable change in one observing frame happen to both objects of concirn equally. No one object in total seclucion has any determinable or relative value. Only with a minmum of two objects can anything happen and an equation be written. And with these two objects alone, they exist on either sides of an equal sign.

 

Anything that happens on 1 side of the equation must happen on the other side to have it remain correct. Yet if we accept this in the fundementals of reality it is what creates the quantized observations.

 

For there is Never a rest, or a end to frequency. So there can never be a value between 0 and the first detectable microscopic action. And in that first action, it is two that are involved, and two that are equal in action and reacting.

 

So when we increase an objects velocity the energy (f*d) that it is capable of doing increases with the square of its velocity because as the object it interacts with is stuck in the same equation.

 

1):hihi: Furthermore on quantized action in relativistic view, and explaining C, and the quantum action of energy.

 

Consant C is equal to the hertz of electromagnetic x the wavelength of electromagnetic waves in one stage of quantum change.

 

C = Hertz X Wavelength

 

Radio Wave [3 x 10^9 (frequency Hz)] X [10cm(wavelength)] = 300,000,000m/s ©

 

The velocity of C is the constant of such because the frequency of energy has a 0 point and the wavelength of energy has a 0 point and the stages of quantum action make up C. The stages of points along this radioactive spectrum is a total which will add up to C (and deviding this value of C with the quantized stages of energy of this scale will give the length/size of a photon(?) or source of photon. To eleaborate, a frequency can only go as low as such before it is gone or zero, and a wavelength can only get as short as such before it becomes stuck together. And the increase of a value causes and equal value on a recieving end, causing a quantized change.

 

We look at 4 objects. 01 and 04 in rest, and 02 and 03 in motion towards eachother.

 

Diagram looking like this.

 

O1<---- O2---> <---O3 --->O4

 

each object is we consider at velocity of C. C+ means two objects coming together.

 

O1(V= -C)<---- O2(V= +C)---> <---O3(V= +C) --->O4(V= -C)

 

 

Here we draw the wavelength/frequency shift bewtween the drawing of moving objects when objects have reached the value of C.

- is zero frequency (flat line impossible in space-time)

| is zero wavelength. (no wave length impossible in space-time)

 

O1--------O2|||||||||||||||O3---------O4

 

 

Where as when objects are not breaking the constant rule we have frequency and wave length again with changes.

 

O1~ ~ ~ ~ ~ ~O2~~~~~~~~O3~ ~ ~ ~ ~ ~O4

 

 

 

 

Havig these objects (02 and 03) moving just under the constant would allow for a waves (frequency and wavelength of electromagnetic radition) to form between the objects because the constant is no longer being broken. Because the doppler effect has not been taken to a un accomplishable ammount. (excuse the horrid typing artwork).

 

 

Objects that try to seperate or gain at C should cause a dead end relationship between light in between them. Objects can not reach velocity of C. The shift in energy (EMR) will break the constant.

 

In between 0 (no wavelength) and 0 (stopped frequency) we have C (the constant of space-time) and Time (due to frequencies inside the parenthesis of this scale.

 

this can be shown in using

 

Where right away we can see when traveling at velocity of light 1-V/C / 1+V/C = 1-3x10^8/3x0^8 turns into 1-1 turns into 0/1-V/C turns into the square of 0 and therefore we see with the current 0 located in this equation the frequency detected will be end up as 0 when the equation is derived solved.

 

Space-time will be broken down if an object travels at C.

What this is showing with the 4 objects and only 2 are moving from the one observation frame, all 4 experience an impossible doppler effect. And to try and logically back up that both objects move on either sides of a dual observation equation that I tried.

 

The motion of two bodies able to be both considered moving may require to state the universe is non absolute, infinite, or part of infinite persay to allow the motion of one object to not be related to the motion of another object. Meaning If I though A rock, it slows down and speeds up in relation to something in the universe at the same time.

 

I will stop for now. There is more, but I'd like to work in bits.

[arkain101]

*deleted*

[Lsos]

Kinetic Energy is defined as KE = ½mv², but a trivial thought experiment says it just has to be K = mv. The underlying problem seems to be with Work = Force x Distance, which ought to be Force x Time.

 

You’re sitting on a 100kg sled on a frozen lake, with a spring gun that fires a puck backwards. The recoil accelerates the sled forwards to a velocity of 0.1 meters per second.

.

.

With the assistance of a snowcat crew running alongside with a supply of pucks you fire the spring gun a further nineteen times in quick succession, and the sled is now travelling at 2 meters per second.

 

You recalculate the spring energy as 2 x ½ mv² / 20 -> 100 x 4 / 20 = 20 Joules.

.

.

Can anybody point out the flaw in this? Because I sure as hell can't, and it affects everything. Like the dimensions of energy. Which threatens E = MC².

 

I don't know if this has been answered or pointed out already, as I just skimmed the thread. But, the fundamental flaw you're asking for is this:

 

With the assistance of a snowcat crew running alongside with a supply of pucks you fire the spring gun a further nineteen times in quick succession, and the sled is now travelling at 2 meters per second.

 

Assistance means you're adding energy into the system that you haven't accounted for. I can't even push a small car to 1 mph...even though it takes probably the same amount of force to get it up to 2 or 3 or maybe even 20mph. I'm sure if I had the assistance of another car then I could probably push the original car much faster. Even though my arms can only supply the same weak force, the assisting car is supplying the velocity, which in this case makes up most of the energy.

 

Another thing, work cannot be Force x Time, because if it was then I would have done 784N x 8100seconds = 6350400joules of work sitting on my *** half asleep in my office because I partied until 3am last night. The fact is, no work has been done. None.

[arkain101]

Refering to the above example of pushing a car.

 

When we push from ground the ground is rest and the car moves. Our energy to accelerate the car needs to increase as the car's velocity increases.

 

However when we look at a rocket, it is not the same. It is only the transfer of mass. Yet a rocket actually has a top speed.

Lets say it does a burn and reaches 5000km/h in space, then shuts off and coasts for awhile. The fuel in the rocket is now at par with the fusilage/rocket.

It does another burn and reaches 10,000km/h.

And after a break it does another, 15,000kkm/h.

 

So a rocket has a maximum speed, yet it has no original rest state where the fuel pushes from. It meerly transfers momentum.

 

So if I remember right, this is part of relativity that says, eventually the rocket will become too massive (as it speeds up) to accelerate. Although I get confused in this part.

 

How can the relationship change between the fuel speed in the rocket and the exhaust gasses?

Even though the rocket speeds up, the fuel onboard is at the same velocity and is increases with the rocket. Each new burn is like the first, and although the fuel will appear to exit the rocket slower from earth as the rocket speeds up, from the rockets point of view the fuel remains shooting out at the same speed.

What goes on here? anyone?

 

Do rockets really run into relativity problems?

Or did I read false information at wikipedia about rockets running into a maximum acceleration rate.

[CraigD]

… But, the fundamental flaw you're asking for is this:

With the assistance of a snowcat crew running alongside with a supply of pucks you fire the spring gun a further nineteen times in quick succession, and the sled is now travelling at 2 meters per second.

Assistance means you're adding energy into the system that you haven't accounted for.

Though it’s true the “assistance of the snowcat crew” adds a small amount of energy and momentum to the sled-pucks system, the problem’s “trick” works as well with a sled and a “repeating spring gun” pre-loaded with 20 pucks. The most significant flaw is that the problem falsely asserts that each puck has not only an equal and opposite momentum to the sled (true), but an equal and opposite kinetic energy (false).

I can't even push a small car to 1 mph...

On a practical note, if you’re physical average, you’d likely discover that, on smooth level pavement, you’re able to push an average car up to a speed of 5 MPH or more. Those of us with older cars with manual transmissions and unreliable starters have plenty of experience with such techniques. :dead:

Another thing, work cannot be Force x Time, because if it was then I would have done 80kg x 8100seconds = 648000joules of work sitting on my *** half asleep in my office because I partied until 3am last night. The fact is, no work has been done. None.

An excellent example of a fairly large force and long time acting over a nearly zero distance to perform nearly zero work. :dead:

[arkain101]

So if we were to squish an object in a force field to the point where it melts down and glows, would it remain at that 'tempeture' if you were to leave it compressed? (assuming of course, nothing physical interacted with it.)

 

If so, could we spin a very strong ring like object in a vacume (assume zero gravity) and put a soft, low tempeture metling material on the inside of the ring, could we heat cause the pressure to heat that material and have it continued heating? I think would work in theory, but would be hard to engineer. I suppose we could only use the radiation heat coming off?

 

What do you think Craig? I like your responses.

[CraigD]

Do rockets really run into relativity problems?

Or did I read false information at wikipedia about rockets running into a maximum acceleration rate.

No rocket built by man has yet experienced significant relativistic “mass dilation”, because none has accelerated to anything close to a substantial fraction of the speed of light.

 

What limits the maximum change in velocity a practical rocket can achieve is it’s mass ratio – the fraction of its total mass that it must expel as reaction mass. The equation for mass ratio is:

[math]\frac {m_0} {m_1} = e ^ { \Delta v / v_e }[/math]

, so, for a really good modern chemical rocket engine with an exhaust velocity of 6000 m/s to accelerate a 1000 kg (compact car size) payload to a speed of 300000 m/s (0.1% the speed of light), it must “burn” about [math]{2.7}^{50} = 5*{10}^{24}[/math] kg of reaction mass – about the mass of the Earth!

 

For a rocket to beat these “cold equations”, it needs to have vastly higher exhaust velocities. Much of advanced rocket research seeks to do just that. Other spaceflight research (eg: “laser light sails”) is focused on abandoning the whole “carry you reaction mass” approach of conventional rockets.