- #31
Hellmut1956
- 43
- 18
Dear Cecil, as PeterDonis refreshingly correct stated, the energy of 2 bodies falling from a place onto each other having been at rest at the starting point just converts potential energy in kinetic energy. What you write is at least not complete. If a body is raised in afield its potential energy is increased and this energy has to be added to the system from external. I like to call it energy pump! As a consequence when an object "is lowered in a gravitational field" you do not write if an external force is applied, this would mean that energy is added to the system and this energy would add to the potential energy converted in kinetic energy by an object moving down "a field". We see this when we watch a spacecraft coming back to Earth after visiting the space station! Chemical energy is burned to reduce the amount of kinetic energy of the spacecraft while being in orbit with the space station! So if "something lowers an object" in a field moving it from a higher potential energy level to a lower energy level, this would add kinetic energy to the one generated from converting potential energy to kinetic energy!
You are correct when you say that reducing the potential energy in a water reservoir, giving as an example a hydroelectric dam, energy gets converted to kinetic energy embodied in the mass of the water falling from the reservoir to the bottom and that a turbine converts a part of this energy i.e. into electrical energy. Where you are totally wrong is in putting the analogy with a nuclear plant as a mean to convert mass to energy!
A hydroelectric plant converts a part of the kinetic energy resulting from the water loosing potential energy and converting it into kinetic energy which the generator uses to create electrical energy. The mass of the water while "embodying" the kinetic energy does remain unchanged as to its mass.
A nuclear plant works using completely other kind of energies! In a nuclear plant atoms are split releasing energy as radiation, heat being a part of this radiation! The source of this energy comes from the forces in the atom nucleus and in the nucleus the physics there behave by the means that mass and energy are just 2 conditions energy can have. Mass and energy there are equivalent! So a part of the radiation generated radiates with the wavelength of heat and so it heats up the water in the primary circuit. This heated water is used to heat water in the secondary water circuit just to keep radioactive radiation confined. The water is converted to gas which increases its pressure and as a consequence this gas moving to areas in the circuit with less pressure, kinetic energy, moves the generator that delivers the electricity! To reuse this water in the secondary circuit it has to be cooled down as it is well known in the cooling towers you see next to atomic plants. In a certain sense, most of the energy available due to the atomic reactions is converted into vapor which reflects the poor efficiency of such atomic reactors!
this picture being in german is till readable for readers in other languages!
I am studying right now a variation of physics didactics called system physics and that is based on "karlsruher physics course" that uses the concept that you took as an example with the water damn to describe physics by having physical quantities embodied in a volume and of potentiality fields. Fascinating about this is, that all areas of physics, be it the classical physics, or be it quantum and relativistic physics, but also fluids, thermodynamics, chemistry and rotational and translational mechanics can be described using the same algorithmic equations and the concepts of potential energy either flowing freely from a recipient with a higher potential to a one with a lower potential releasing energy as the result of the difference of the potential energies or requiring a "pump" that pumps energy in the system. To take your example of the water damn again. A way to store energy in a public grid is to pump water from a lower reservoir to one with a higher potential energy level. Here the water pump converts electrical energy into potential water energy by transporting water volumes between the reservoirs.
I have taken the picture of the above table to show the 7 physical quantities and their related fields that result in a "potential energy level" of a reservoir! This style of teaching physics, besides the fact it allows to model problems and simulate them using tools available for "system dynamics", a concept developed by the Sloan Institute at MIT in 1956, I love the tool "Berkeley madonna" and the modeling and simulation language "Modelica" that represent powerful tools.
Just to wake your interest, http://www.physikdidaktik.uni-karlsruhe.de/Strategien/Analogien_englisch.html a link to a resource available at http://www.physikdidaktik.uni-karlsruhe.de/Strategien/Umwege_englisch.html website. http://www.physikdidaktik.uni-karlsruhe.de/publication/ejp/kpc_ejp.pdf the link to an interesting pdf archive and here 2 pictures that should be of interest:
This table taken from the above linked pdf archive shows how the same kind of simple algebraic equations apply to fields of physics normally seen as completely separated. if you keep in mind that physics is just a science that generates models that allow to predict and compute events observed in real or that are used to be searched for, then this view points on physics without reinventing the wheel displays similarities between the different fields of physics, just by applying the methodology used to model complex dynamic systems developed by the Sloan Institute of MIT in 1956. I found this to be very interesting perspective, as it enables me to model what i believe I have understood and verify my understanding by analyzing the results of the modeling and simulation!
This picture shows the inelastic collision as an example shown using a fluid picture that is well suited to represent the facts using the didactics of System Physics.
This final picture I want to add just as an appetizer to look into system physics:
I am presenting all this as it allows to look in more detail into the misconceptions presented by Cecil in this thread and at the same time offers an alternative to correctly dwelf into what Cecil and others have been trying to say. As I wrote elsewhere, try to get more into the topic before just presenting wild not organized and even less understood topics being reflected about!
I, myself want to write, that I am an apprentice who is trying to educate himself in the required mathematics and physics, because on one side I always have had an affinity to physics, but I am also studying it because I am learning the skills required to model a subsystem I am having a concept of in my hobby of naval modeling.
You are correct when you say that reducing the potential energy in a water reservoir, giving as an example a hydroelectric dam, energy gets converted to kinetic energy embodied in the mass of the water falling from the reservoir to the bottom and that a turbine converts a part of this energy i.e. into electrical energy. Where you are totally wrong is in putting the analogy with a nuclear plant as a mean to convert mass to energy!
A hydroelectric plant converts a part of the kinetic energy resulting from the water loosing potential energy and converting it into kinetic energy which the generator uses to create electrical energy. The mass of the water while "embodying" the kinetic energy does remain unchanged as to its mass.
A nuclear plant works using completely other kind of energies! In a nuclear plant atoms are split releasing energy as radiation, heat being a part of this radiation! The source of this energy comes from the forces in the atom nucleus and in the nucleus the physics there behave by the means that mass and energy are just 2 conditions energy can have. Mass and energy there are equivalent! So a part of the radiation generated radiates with the wavelength of heat and so it heats up the water in the primary circuit. This heated water is used to heat water in the secondary water circuit just to keep radioactive radiation confined. The water is converted to gas which increases its pressure and as a consequence this gas moving to areas in the circuit with less pressure, kinetic energy, moves the generator that delivers the electricity! To reuse this water in the secondary circuit it has to be cooled down as it is well known in the cooling towers you see next to atomic plants. In a certain sense, most of the energy available due to the atomic reactions is converted into vapor which reflects the poor efficiency of such atomic reactors!
this picture being in german is till readable for readers in other languages!
I am studying right now a variation of physics didactics called system physics and that is based on "karlsruher physics course" that uses the concept that you took as an example with the water damn to describe physics by having physical quantities embodied in a volume and of potentiality fields. Fascinating about this is, that all areas of physics, be it the classical physics, or be it quantum and relativistic physics, but also fluids, thermodynamics, chemistry and rotational and translational mechanics can be described using the same algorithmic equations and the concepts of potential energy either flowing freely from a recipient with a higher potential to a one with a lower potential releasing energy as the result of the difference of the potential energies or requiring a "pump" that pumps energy in the system. To take your example of the water damn again. A way to store energy in a public grid is to pump water from a lower reservoir to one with a higher potential energy level. Here the water pump converts electrical energy into potential water energy by transporting water volumes between the reservoirs.
I have taken the picture of the above table to show the 7 physical quantities and their related fields that result in a "potential energy level" of a reservoir! This style of teaching physics, besides the fact it allows to model problems and simulate them using tools available for "system dynamics", a concept developed by the Sloan Institute at MIT in 1956, I love the tool "Berkeley madonna" and the modeling and simulation language "Modelica" that represent powerful tools.
Just to wake your interest, http://www.physikdidaktik.uni-karlsruhe.de/Strategien/Analogien_englisch.html a link to a resource available at http://www.physikdidaktik.uni-karlsruhe.de/Strategien/Umwege_englisch.html website. http://www.physikdidaktik.uni-karlsruhe.de/publication/ejp/kpc_ejp.pdf the link to an interesting pdf archive and here 2 pictures that should be of interest:
This table taken from the above linked pdf archive shows how the same kind of simple algebraic equations apply to fields of physics normally seen as completely separated. if you keep in mind that physics is just a science that generates models that allow to predict and compute events observed in real or that are used to be searched for, then this view points on physics without reinventing the wheel displays similarities between the different fields of physics, just by applying the methodology used to model complex dynamic systems developed by the Sloan Institute of MIT in 1956. I found this to be very interesting perspective, as it enables me to model what i believe I have understood and verify my understanding by analyzing the results of the modeling and simulation!
This picture shows the inelastic collision as an example shown using a fluid picture that is well suited to represent the facts using the didactics of System Physics.
This final picture I want to add just as an appetizer to look into system physics:
I am presenting all this as it allows to look in more detail into the misconceptions presented by Cecil in this thread and at the same time offers an alternative to correctly dwelf into what Cecil and others have been trying to say. As I wrote elsewhere, try to get more into the topic before just presenting wild not organized and even less understood topics being reflected about!
I, myself want to write, that I am an apprentice who is trying to educate himself in the required mathematics and physics, because on one side I always have had an affinity to physics, but I am also studying it because I am learning the skills required to model a subsystem I am having a concept of in my hobby of naval modeling.