…Energy is the only thing that can niether be created nor destroyed…it can only be transformed in its nature…PT. 2…and it always adds up to zero…
What does the: “always adds up to zero”, mean in the most simplistic layman terms please?
As I must have cut more school than I thought or remember…where can I get a list of the rest of the physical laws of the universe, for the layman or most simplistic understanding?
For example…the law of thermal dynamics was explained to me…if you leave a brick out in the elements, does it improve or brakedown over time?
I picked errosion to be a factor here…so…I think I might grasp what is going on here.
Any other good tips for understanding the most basic laws?
How many basic laws are there, by the way?
As I recall from HS physics and chemistry, the following is the actual definition of energy:
. Therefore, when somone talks about it “always adding up to zero”, they are referring to the law that energy is always conserved. Meaning that energy is neither created nor destroyed. It can be changed from one form to another, therefore if you can quantify one type of energy before it is transformed into another, and then quantify it after it has been transformed, the two will cancel each other out.
BTW, the 3 laws of thermodynamics are as follows:
Energy is neither created or destroyed (Conservation of energy)
The entropy of a closed system increases with time (Things tend to move toward disorder on their own).
When two bodies are each separately in thermal equilibrium with a third body, then all three bodies are in thermal equilibrium.
Energy is the ability to do work. If a baseball is sitting still beside a stack of blocks, it can’t do anything to the blocks. It’s just sitting there. If, however, the baseball is whizzing through the air towards the blocks, it has energy-- it can hit the blocks and make them move too.
‘Adding up to zero’, as the previous poster said, is a catchphrase that means all the energy has to come from somewhere. If the baseball is moving, it has energy that it got from somewhere else-- probably a person threw it, which means the person gave energy to the ball. Where did the person get the energy? It was stored energy that they got from eating food (they converted it from chemical energy). And so on.
I don’t understand that at all. If I have a box bisected by a barrier, with one side of the board very hot and the other very cold, then I can do work. If I open the barrier and allow the heat to diffuse, the energy doesn’t go down, but my ability to do work does. Eventually I will be able to do zero work, yet the energy content of the box will have not changed.
Feynman defined energy as a number that does not change. That is in either his lectures, or his book The Character of Physical Law. Has to be, those are the only things by him I’ve read, IIRC.
Entropy will have increased (in keeping with the 2nd law) but the total energy is the same; to use a very simplistic example, suppose in your example you had a known amount of gas at 40 degrees C on one side of the barrier, and the same amount at 0 on the other. The average temperature (which we can think of as energy, in that it’s a measure of how much kinetic energy a molecule has and hence how fast it’s moving) over the whole box is 20. Open the barrier, mix it up and the average temperature after mixing is still 20.
You can still use that energy to do work, but not within the confines of the box - you’d have to look at a larger system containing the box rather than the box as a closed system.
Dragwyr: You have confused the third law of thermodynamics (dealing with entropy of substances at absolute zero) with the zeroth law of thermodynamics (the definition of temperature) - called out at the bottom of your cite.
As to the OP: energy always adding up to zero means that if you do your accounting properly you should be able to tell where all your starting energy went.
How many fundamental laws should you know? Newtonian laws of motion are a decent place to start. Conservation of mass, momentum, energy, charge, and species are all useful in engineering. Inverse square law and square-cubed law are both useful to understand certain types of interactions. Probably could come up with dozens more, and I am sure other posters will.
I am not sure erosion is a great example to start with. For example, of the three laws of thermodynamics only the second law would really easily apply (and it would basically state that rocks, once eroded, are unlikely to spontaneously unerode)
Things, are of course, a little more complex than energy always adding up to zero. In the short term, energy can be “borrowed” from the void, though it always must be paid back. And energy and mass can be converted from one to the other (see “nuclear weapon” for the most impressive example, although it happens all the time) though the total sum of mass-energy remains constant.
The energy in the box has not changed, but the ability to do work in the box has. This suggests to me that energy and ability to do work are orthogonal (for lack of a better word), which leads me to ask if the definition of energy as the abilitiy to do work is really an appropriate one.
Is my mistake the fact that I am not accounting for the fact that the box is within a larger system, to which it can be exposed? If so, isn’t the larger system just a larger box to increase entropy w/out losing energy? I’m sure you can see where this is leading me: If the energy in the universe doesn’t change but entropy increases, then the ability to do work in the universe goes to zero and energy holds constant, thus rendering ability to work and energy orthogonal in the universe. So it still seems inappropriate to define the latter as the former.
This is (to my understanding) what is happening, albeit that it takes a very long time. I believe one of the possibilities that cosmologists think may happen eventually (and we’re talking a long time in the future) is so-called ‘heat-death’ where the entropy of a closed system (the universe) is at its maximum; everything is at the same temperature and nothing can happen (no physical process, life etc). What we need is an astrophysicist (channelling Angua et al) to confirm it (IANAA)…/Xerx