Energy and momentum.The misunderstanding have prevailed

• Themistocles
In summary, the conversation discusses the concept of energy and momentum, particularly in the context of a collision between two train wagons. The conservation of momentum is used to find the velocity of the wagons after the collision, and it is noted that there is a loss of kinetic energy. The conversation also touches on the understanding of energy in classical mechanics and the idea of energy transforming into heat and sound. The concept of a system is also mentioned and the importance of considering the system as a whole rather than focusing on individual particles.
Themistocles
Energy and momentum.The misunderstanding has prevailed

Two train wagons of the same mass will impact.
Wagon A has velocity 10 and wagon B 0.When they impact a lock will make them conjoint.
Which will be the velocity of two wagons and which the energy after the collision;

We use the conservation of momentum (...not the energy)and we will find
that the velocity will be 5.We note that we have a loss of KE. AND we say with endless silliness and easiness that kinetic energy transformed to heat (and sound) the simple logic obey me to ask: <<<<<How the particles of the wagons have heat without momentum? Since all the momentum is visible to us, as velocity of the wagons.>>>>>>

All we know that must eventuate to the conservation of two quantums K.E. and P (for the most is only equations because of misunderstanding of the real meaning)

I think that few know their nescience , fewer know it, but can not do anything to learn ( ineffectual searching on books ,web).The people who know is the rarest.
I want to know the fundamental of physics like a scientist and no like accountant who has memorized the methods of solving problems and finish them automatically and ignores what the represent
Despite the previous i have a thought of the "two wagons" in the case of pendulum and bullet...

-We have answer of relativity that energy represents the matter.
-In 19th century scientists had disagreement of which of two quantums represent the element of difficulty to change velocity(see halliday and resnick book).Note that force is not the ordinary word ,people use ,it is a mathematical variable.Also they had engrossment how the same force to same object need different energy supplys depend of its different previous velocity.

If you have understand the collision of different mass object "in action-reaction level" the meaning of energy in classical mechanics

Last edited:
Themistocles said:
<<<<<How the particles of the wagons have heat without momentum? Since all the momentum is visible to us, as velocity of the wagons.>>>>>>

The 'vibration' components of the particles' velocities, that result in heat energy actually cancel out, resulting in zero momentum due to heat. There are billions (much greater order actually) of particles where the probability of vibrating at any direction is the same.

ramollari said:
Mi pos file mporeis na to grapsis sta Agglika epidi ego dixtihos den eimai Elinas (spoudazo sti Elada) kai den to katalaveno sosta. Evxaristo.
c c
c b-> c
ccccccccccccc
We have a container and a bullet (of the same mass for easiness)
bullet is inside and has a speed from left to right.when it impacts to the right wall of the container ,it stops and the container now move.because practically we can not see inside the container or because the impact are continual and fastly we observe that the system moves constant with the half of course, speed.

So what's the problem? Momentum is conseved m1v1 + m2v2 = (m1 + m2)v
Overall energy is also conserved (Kinetic + heat + sound). Of course the kinetic energy of the system is decreased.

ramollari said:
So what's the problem? Momentum is conseved m1v1 + m2v2 = (m1 + m2)v
Overall energy is also conserved (Kinetic + heat + sound). Of course the kinetic energy of the system is decreased.
but we cannot separate the system.the system consists from the bullet and container .they have the quantums.And we want to examine exactly how the energy and momentum exists on it.Of course it is easily for us when the object is like a wooden pendulum which harmed by a bullet(complicated situation) to simplify the problem .ans say that energy went at heat and sound and ignoring how the particles have thermal-move without momentum.
i think your first reply is near the example of the container and bullet.
The essenetial is that if we don't want to conflict we must think of intermitent move of the system

We cannot take every single particle and compute its movement! Yet if we could, we would still get consistent results.
But it is more useful to abstract and view the system as two bodies where momentum is conserved and just say that the energy is lost as heat and sound, i.e. we take a more global perspective.

1. What is the relationship between energy and momentum?

The relationship between energy and momentum is that they are both conserved quantities in a closed system. This means that the total amount of energy and momentum in a system will remain constant, even if they are converted from one form to another.

2. How are energy and momentum related to each other mathematically?

The mathematical relationship between energy and momentum is given by the equation p = mv, where p is momentum, m is mass, and v is velocity. This equation shows that momentum is directly proportional to both mass and velocity.

3. Can energy and momentum be transferred between objects?

Yes, energy and momentum can be transferred between objects through different forms of interactions, such as collisions or explosions. This transfer can result in changes in the velocity and direction of the objects involved.

4. What are some common misconceptions about energy and momentum?

One common misconception is that momentum is the same as force, when in fact force is the rate of change of momentum. Another misconception is that energy can be created or destroyed, when in reality it can only be converted from one form to another.

5. How do energy and momentum play a role in everyday life?

Energy and momentum are essential concepts in understanding and predicting the behavior of objects in motion. They are also crucial in fields such as engineering, physics, and even sports, where understanding the transfer and conservation of these quantities is important for performance and safety. Additionally, many renewable energy sources, such as wind and hydro power, rely on the conversion of energy and momentum to generate electricity.

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