otseng wrote: ↑Wed Jun 19, 2024 6:51 amHow does dropping a rock and causing a dent and busting up and generating a little heat
violate the first law of thermo?
This is the problem we had when we were discussing geology. You write something that seems reasonable, but means something completely different to you than it does to everyone else. If by "little heat," you mean anything other than virtually the entire amount of potential energy initially in the rock, then you're violating the first law of thermodynamics.
Since ChatGPT seems to be the way you want to go, I had a brief conversation. I asked:
Difflugia wrote:In a room that is a closed system with regard to energy, there is a 1kg stone weight suspended 1m above a stone floor. If the weight is released and the system allowed to come to rest, what is the final form, amount, and distribution of the initial potential energy from the weight?
It responded:
ChatGPT wrote:To analyze the situation in the closed system, we'll consider the energy transformations that occur when the 1 kg stone weight is released and allowed to come to rest.
- Initial Potential Energy:
- The stone weight initially has gravitational potential energy given by Ep = mgh.
- Here, m = 1 kg, g = 9.81 m/s (acceleration due to gravity), and h = 1 m.
- Therefore, Ep = 1 kg 9.81 m/s2 1 m = 9.81 J.
- Energy Transformations:
- When the weight is released, its potential energy is converted into kinetic energy as it falls.
- Upon hitting the stone floor, the kinetic energy is then converted into other forms of energy, primarily:
- Heat energy due to the impact and friction.
- Sound energy from the noise of the impact.
- A small amount of energy may also be used to slightly deform the weight and the floor (elastic potential energy).
- Final Distribution of Energy:
- Heat Energy: A significant portion of the initial potential energy will be converted into heat energy, warming the stone weight and the floor at the point of impact.
- Sound Energy: Some of the energy will be dissipated as sound waves, which will eventually also be absorbed by the surroundings as heat.
- Deformation Energy: Any deformation of the stone weight or the floor will store a small amount of energy temporarily as elastic potential energy, but this too will likely convert into heat as the materials return to their original shapes or settle into new configurations.
- Final Form of Energy:
- The majority of the initial 9.81 J of potential energy will be in the form of heat energy within the room.
- A small amount of energy will have been briefly in the form of sound energy, which will also ultimately dissipate as heat.
- Distribution of Energy:
- The heat energy will be distributed among the stone weight, the stone floor, and the air in the room.
- The precise distribution will depend on the specific heat capacities and thermal conductivities of the materials involved, but generally, the stone floor and weight will absorb most of the energy, with a smaller portion warming the air in the room.
Summary:
- Final Form of Energy: Primarily heat energy.
- Amount of Energy: 9.81 Joules (initial potential energy).
- Distribution of Energy: Mostly in the stone floor and weight, with some distributed into the air as heat.
The closed system ensures that the total energy remains constant, transforming from gravitational potential energy into heat energy predominantly, with temporary and minor conversions to kinetic and sound energy.
Does this match what you expected? Why or why not?
otseng wrote: ↑Wed Jun 19, 2024 6:51 am
"Work" isn't a form of energy. After "work was done," something has to still be moving, in a higher energy state, or hotter. A broken rock at rest on the floor is none of those.
This is where the second law of thermo comes in. Energy is still constant in the total system, but the amount of usable energy has decreased.
Whether usable or not, what form is that energy in? Kinetic? Potential? Thermal? If something else, then what?
otseng wrote: ↑Wed Jun 19, 2024 6:51 amIf you hit a rock with a hammer and break it, all of the energy you put into swinging the hammer and breaking the rock ultimately ends up as heat.
Let's ask ChatGPT:
Now let's ask ChatGPT and ask it to quantify the answer.
Difflugia wrote:If I break a rock with a hammer using 10N of force, all of the energy is transferred into the rock, and the fragments are allowed to come to rest, in what forms and in what amounts is that initial energy stored in the final system?
Here's ChatGPT's answer:
ChatGPT wrote:When you break a rock with a hammer using 10N of force, the initial energy you apply is transferred into the rock and converted into several forms of energy as the rock fragments. The forms and approximate amounts of energy stored in the final system can be broken down as follows:
- Elastic Energy: Before fracturing, some of the applied force is temporarily stored as elastic energy in the rock. Once the rock breaks, this energy is released and converted into other forms of energy.
- Fracture Energy: The primary form of energy where most of the applied force goes is into creating new surfaces within the rock. This involves breaking the chemical bonds (ionic, covalent, metallic, etc.) in the rock. The energy required to create these new surfaces is called fracture energy.
- Sound Energy: Some of the energy will be released as sound waves. This is the noise you hear when the rock fractures.
- Thermal Energy: The process of fracturing the rock generates heat due to internal friction and the breaking of bonds. This increases the temperature of the rock fragments and the surrounding environment slightly.
- Kinetic Energy: Immediately after the impact, the fragments of the rock may move away from the point of impact. This motion represents kinetic energy. However, as the problem states that the fragments are allowed to come to rest, this kinetic energy will eventually be converted into other forms, primarily thermal energy due to friction.
- Potential Energy: In some cases, if fragments are displaced and fall to a lower position, there could be a small amount of gravitational potential energy converted from the initial kinetic energy.
To quantify the amounts, assuming 10N of force is applied over a very short distance (a hammer strike), let's simplify the energy distribution:
- Fracture Energy: A significant portion of the energy goes into creating new surfaces (breaking bonds). The exact amount depends on the rock type and its fracture toughness. For simplicity, let's assume a large fraction, say 6080%.
- Sound Energy: This is typically a small fraction of the energy, likely around 510%.
- Thermal Energy: The combination of kinetic energy dissipation and internal friction results in heat. This can be around 1020%.
- Kinetic Energy: Initially, the fragments have kinetic energy, but since they come to rest, this energy will convert to thermal energy and, possibly, a negligible amount to potential energy. The initial kinetic energy might be 1020%, which then transfers mostly to thermal energy.
Given this, a rough estimate of the energy distribution would be:
- Fracture Energy: 68Nm (or Joules)
- Sound Energy: 0.51Nm (or Joules)
- Thermal Energy: 12Nm (or Joules)
- Kinetic Energy: Initially 12Nm (or Joules), eventually converted to thermal energy
These values are approximations and the exact distribution depends on specific conditions such as the type of rock, the precision of energy transfer, and environmental factors.
Now, there's a problem with this. "Fracture energy" isn't permanently stored, so in effect, ChatGPT is using a different definition of "at rest" than I am and is telling us the distribution at the moment of fracture. Since I know this, I had to prompt ChatGPT a bit.
Difflugia wrote:How is stored fracture energy subsequently released?
ChatGPT then finished its answer:
ChatGPT wrote:The stored fracture energy in a rock, once it has fractured, is subsequently released in several ways:
- Sound Energy: Part of the fracture energy is released as sound waves. The cracking sound you hear when a rock breaks is a result of the rapid release of energy as the bonds break and the rock fragments.
- Thermal Energy: The breaking of bonds and the friction between the newly created surfaces generate heat. This thermal energy increases the temperature of the rock fragments and the surrounding air, although the temperature rise might be quite small and often not noticeable.
- Kinetic Energy: When the rock fractures, the fragments may move apart due to the release of stored energy. This kinetic energy is evident immediately after the fracture as the pieces fly apart. However, as mentioned, if the fragments are allowed to come to rest, this kinetic energy is eventually dissipated, mostly as thermal energy through friction with the air and the ground.
- Elastic Waves: Some of the energy is released as elastic waves that propagate through the rock and the surrounding material. These are essentially seismic waves, and in the context of a hammer strike on a rock, these are very small and localized.
To summarize, the fracture energy stored in the rock is released mainly as:
- Sound Energy: Audible cracking noise.
- Thermal Energy: Heat generated by the breaking bonds and friction.
- Kinetic Energy: Motion of rock fragments, which is subsequently converted to heat as fragments come to rest.
- Elastic Waves: Small seismic waves.
These processes ensure that the initial energy applied to the rock is fully accounted for in various forms of energy, following the principle of conservation of energy.
Does this match what you expected? Why or why not?
otseng wrote: ↑Wed Jun 19, 2024 6:51 amAnd I'm trying to apply the discussion of thermodynamics to the actual debate. Diverting the discussion back to the flood would be the one deviating from the current discussion.
I said you didn't understand thermodynamics based on the arguments you made during the Flood discussion. You said you were "willing to dive into this again." If you've changed your mind, that's fine.
otseng wrote: ↑Wed Jun 19, 2024 6:51 amAnd you also seem to ignore the second law of thermo and also ignore the debate on the current topic.
The first law and second law of thermodynamics are independent. I'm working through your misunderstanding of the first law. If we can get through this, we can work on the second law if you want.
otseng wrote: ↑Wed Jun 19, 2024 6:51 amThe energy also caused the spring to move, which would be work.
"Work" is the transfer of energy from one form to another. It doesn't
consume energy as such. It's counterintuitive at first because we're so used to friction in the real world bleeding off energy as heat, but that's the crux. Without friction, the spring-weight system would oscillate forever as the energy is converted from gravitational-potential to kinetic to elastic-potential to kinetic to gravitational-potential. At each transition, "work" is done without the energy being consumed or going anywhere. When friction is introduced, each interaction causes a little kinetic energy to become heat energy until ultimately all of the energy in the system is in the form of thermal energy.
otseng wrote: ↑Wed Jun 19, 2024 6:51 amYou're going to have to cite a source that says
all energy in a system would ultimately be converted into heat.
This is from
Fundamentals of Physics I : Mechanics, Relativity, and Thermodynamics, Expanded Edition:
21.7 Heat as molecular kinetic energy
In the old days, people just said that heat was a caloric fluid, and they postulated the conservation law for the fluid. You can postulate what you want, but you have to make sure it works. The conservation of calories did seem to work, in the sense that all the Qs in any reaction did seem to add up to zero. But then people started getting hints that this fluid was not conserved and that this thing we call heat is not entirely independent of other things we have studied.
So, where do you get the clue? When we studied mechanics, we talked about two cars in a totally inelastic collision-they slam into one big static lump; in the end we have no kinetic energy and no potential energy. We just gave up and said, "Look, conservation of energy does not apply to this inelastic collision." On the other hand, we find that in such a collision the bodies become hot. So calories are not conserved either: they are created in a collision. There are more clues. You take cannon balls and drop them from a big tower. When they hit the sand, they start heating up. Or you drill a hole in a cannon to guide the ball, which is what Count Rumford did in 1790, and you find that you need to constantly pour water to keep the drill bit from heating up. You find all the time that, when mechanical energy is lost, things heat up, that is, calories appear from nowhere. So, you get a suspicion that maybe there's a rule connecting the mechanical energy that you cannot account for, that seems lost, to a corresponding gain in calories. Maybe the conservation of mechanical energy and of heat could both be salvaged into a single law of conservation of energy if joules measure energy you can see, and calories energy you cannot see. That is the premise. If that is the case, we must first determine the exchange rate between calories and joules.
James Prescott Joule performed the experiment shown in Figure 21.7. You have an insulated container in which there is water and a shaft attached to fins. The shaft can rotate. At its top is a pulley with a weight hanging as shown. There is a rope wrapped around the shaft, and when you let this weight go down, it's going to spin the shaft. The fins churn up the water. Now, you can keep track of how much mechanical energy is lost, right? This mass was at rest at first and it lost potential energy Mgh as it came down. Let's say it's got some kinetic energy at the end that is less than Mgh. Some number of joules are gone but the water heats up. When the water gets hot, you can ask how many calories were supplied to the water by looking at the mass and specific heat of the water and the increase in temperature. Then you ask if there is a proportionality between the joules and calories. You find it is 4.2 joules to a calorie, called the mechanical equivalent of heat. In other words, if you can expend 4.2 joules of mechanical energy, you get one calorie to be used for heating. In the example of the colliding cars, one car had some kinetic energy, and the other had some ki- netic energy, all measured in joules; they slammed together, and they came to rest. That means you can take all those joules, divide by 4.2, and get some number of calories Q. Then those calories will produce an increase in temperature of the cars, such that Q = mcT, where c is specific heat of whatever material the cars were made of.
In practice, there will be other losses. You heard the crash: that's some sound energy gone; you won't get it back. Some sparks were flying; that's light energy that's gone. You subtract all that out, and you find that in the end, the calories explain the missing joules.
Counting heat as another form of energy, we can save the law of conservation of energy. It is not violated, even during inelastic collisions, if you include heat as a form of energy using 4.2 joules per calorie. What right do we have to call heat energy? When we say some kid is energetic, we mean the kid is always running around mindlessly, back and forth. Energy is associated with motion. These two cars were moving, and we have every right to say they have kinetic energy. How about potential energy then? Well, if the car starts climbing up a hill and slows down, we think it has potential. If you let it go, it will come back and give you the kinetic energy. So, most people think of energy as just kinetic energy. That is what seems to have been lost in the collision. And yet, you get calories in return, so you ask yourself, "How is the calorie related to kinetic energy?"
The correct answer to that came only when we understood that everything is made of atoms. It turns out that the kinetic energy of atoms is what we call heat. But you have to be very careful. I take a cylinder full of very cold gas. I throw it at you. That whole cylinder is moving. That's not what I call heat; the cylinder is not hotter due to its overall motion. That is motion you can see. I'm talking about a cylinder of gas that doesn't seem to be going anywhere; yet it has motional energy because the little guys inside are going back and forth. If you kept track of the kinetic energy of every single molecule in this car, every single molecule in that car, and you added them up, you would get exactly the same number, before and after. The only difference will be that, originally, each car also had some global common velocity, macroscopic velocity you could see. On top of it, it had random motion of the molecules that made up the car. So did the other car. When they slammed together, the macroscopic motion was traded for thermal motion.