NationStates Jolt Archive

1. Can someone please tell me where gravity gets its energy?
2. Is it possible to apply force without using energy?
3. I push the wall for an hour and unsurprisingly it doesn't budge, neither do I. Presumably I use up energy, since I get tired. Well, where did that energy go? I'd say converted to heat to warm up the wall but that appears like the wall would heat up very quickly.

And just to say something almost completely irrelevant; Julius Ceasar.

1. Can someone please tell me where gravity gets its energy? It is not a process requiring energy.

2. Is it possible to apply force without using energy?Yes, put one object on top of another. It applies a force, but if nothing moves, no energy is transformed. (Energy is not used in any real way, just transformed from one form into another, increasing the entropy of the enclosing system)

3. I push the wall for an hour and unsurprisingly it doesn't budge, neither do I. Presumably I use up energy, since I get tired.But if you lean against the wall, you're resting. You still exert a force on the wall, but without using much energy.
When you push, you build up tension, which stores energy, which you need to provide. (That's not the whole story though)

Well, where did that energy go? I'd say converted to heat to warm up the wall but that appears like the wall would heat up very quickly.You don't use that much of energy, besides, you radiate the heat, it is hardly transferred to the wall.

And just to say something almost completely irrelevant; Julius Ceasar.Now there's a man that new how to use force ;)

1. Can someone please tell me where gravity gets its energy?
2. Is it possible to apply force without using energy?
3. I push the wall for an hour and unsurprisingly it doesn't budge, neither do I. Presumably I use up energy, since I get tired. Well, where did that energy go? I'd say converted to heat to warm up the wall but that appears like the wall would heat up very quickly.

And just to say something almost completely irrelevant; Julius Ceasar.
1. No one knows, but gravitons are a (I think) hypothesis. Gravity works by mass - more mass = more gravity. NOT weight.
2. Depends what you mean by force. Remember that something can keep moving without a force behind it.
3. The heat dissipates into the surroundings, also gets converted to kinetic energy hence the pushing. I think. I'm not too good at physics but somehow I got an AA at dual science GCSE.
4. Spelt Caesar wrong. Cææææææsar!

I couldn't help you if I wanted to, I got kicked out of AP Physics for asking a simple question.


If the difference (in H2O) between it being a solid, a liquid and a gas are how close together the molecules are (solid=close, gas=far) then what is inbetween the molecules?

he answered "air"

so knowing that that was the wrong answer, I decided to push further

if the protons and the nuetrons hang out in the middle of an atom and the electrons are floating around on the outside then what is in between the electrons?

he said "air"

"so, inbetween the electrons in an oxygen atom there are hydrogen, nitrogen, oxygen atoms?"

"no, I meant nothing"

"then if there is nothing between them then why don't they stick together"

"there is nothing between them because it's like space where there is nothing"

"you know there isn't any such thing as nothing, everything is something, I just think you don't really know"

"GO TO THE OFFICE AND DON'T COME BACK!!!!!!!!!!!"

I had to transfer to AP Chem:(

I never did get to take physics other than studying on my own.

"you know there isn't any such thing as nothing, everything is something, I just think you don't really know"

The teacher wasn't really wrong, you know. Just didn't know the hows and whys of the answer.

It is thought that this 'nothing' is actually a 'something' in a constant state of flux where particles appear randomly and then disappear in a matter of nanoseconds.

Of course, there could be something even weirder. Maybe even nothing.

The teacher wasn't really wrong, you know. Just didn't know the hows and whys of the answer.

It is thought that this 'nothing' is actually a 'something' in a constant state of flux where particles appear randomly and then disappear in a matter of nanoseconds.

Of course, there could be something even weirder. Maybe even nothing.
I wasn't really trying to annoy him either, I just wanted to know the answer.

He got an attitude, if he would have said "I am not really sure, but you can look it up and we can discuss it" or "nobody really knows, but there are theories about it" I would have been fine with that.

He pulled me aside before class though and said "you have a rep for asking stupid questions and getting teachers fired when they don't know the answer so unless you have anything intelligent to say, then keep your mouth shut in my class"

that was the most intelligent question that was on-subject that I could think of. ;)

1. Umm... Could we leave the gravitons out of this? It's not that I have some sort of embarrassing condition associated with them, but I'd prefer an explanation not using theoretical quantum physics.

Anyway, now that I think of it gravity doesn't really appear to be doing much for entropy. How come? I thought stuff was supposed to try to spread out, not the other way around.

2. But when you push two things together, if you push them really really hard they're supposed to heat up, yet nothing moves. I think. Where did the heat come from?

3. Just to clarify, what I have in mind is more like standing in a 1 meter wide corridor and pushing one wall with your feet and the other with your hands. You know, like they do in the silly spy movies.

4. Yeah, I misspelled it but that isn't really what the "almost" was.

He pulled me aside before class though and said "you have a rep for asking stupid questions and getting teachers fired when they don't know the answer so unless you have anything intelligent to say, then keep your mouth shut in my class"

Yeah, some teachers are like that. Although spending the whole day with all those kids must affect something.

2. But when you push two things together, if you push them really really hard they're supposed to heat up, yet nothing moves. I think. Where did the heat come from?
The heat would have come from the energy used in the attempt to push the two things together.

Edit to clarify: The energy used to push the walls together causes the moleculesto move a little faster. This energy is converted into heat as the molecules move faster and faster, which will dissipate when the energy is taken away.

3. Just to clarify, what I have in mind is more like standing in a 1 meter wide corridor and pushing one wall with your feet and the other with your hands. You know, like they do in the silly spy movies.
Then you are the source of energy, and that energy is transferred into both walls until you don't have the energy to exhibit force onto the wall. The energy is collected as heat, and the molecules of the wall speed up a bit, use up that energy, or pass it on to something else.

No physics is just a stupid subject. Its in so little demand here in Britain that we've got a real shortage of graduates with Physics degrees, meaning that we're somewhat knackered...

1. Umm... Could we leave the gravitons out of this? It's not that I have some sort of embarrassing condition associated with them, but I'd prefer an explanation not using theoretical quantum physics.

It's like a spring. The energy is put by whatever is pulling the spring, gravity is the force that brings it back. In the case of the Universe, it was the Big Bang that provided that energy.

Anyway, now that I think of it gravity doesn't really appear to be doing much for entropy. How come? I thought stuff was supposed to try to spread out, not the other way around.

As I said, it's like a spring. Entropy is energy lost in the process of things spreading out and then getting back. It doesn't go back to the same state it was before. Even if the Universe decelerates (which it seems NOT to be doing) and bounces back, there'll be a limited number of times before it stops completely, unless by some unknown mechanism entropy is reversible.


2. But when you push two things together, if you push them really really hard they're supposed to heat up, yet nothing moves. I think. Where did the heat come from?
What do you mean nothing moves? What about those molecules and atoms that start to vibrate faster by being under pressure?

And comparing the amount of energy you're putting out, with the mass of the wall, it's really very, very little. That's why the wall doesn't seem to heat up at all.

Edit to clarify: The energy used to push the walls together causes the moleculesto move a little faster. This energy is converted into heat as the molecules move faster and faster, which will dissipate when the energy is taken away.

Makes sense, that's what I told my physics teacher too. Only things is, he stopped and pondered it for a while, then said he doesn't know and continued with the lesson.

There is a problem though, how do you move a solid's atoms? I know they're supposed to vibrate, but how can you make something vibrate by pushing it? The string analogy doesn't work.

There is a problem though, how do you move a solid's atoms? I know they're supposed to vibrate, but how can you make something vibrate by pushing it? The string analogy doesn't work.
Atoms are not really solid, solid. There's a lot of space between them. What we actually consider solid is mostly empty space and we just feel the repulsion between billions of electromagnetic fields.

There is a problem though, how do you move a solid's atoms? I know they're supposed to vibrate, but how can you make something vibrate by pushing it? The string analogy doesn't work.
Well, there's no such thing as a solid in the true sense of the word, really. Even the most dense, heavy, solid objects aren't stuck together at the molecular level. They may be close together, but they are seperate from one another. They just move slower.
All "solid" really means is that the molecules don't move so much due to a lack of energy. But when energy is applied, those molecules start moving, and that's how you get the motion of a solid object!

Yeah, some teachers are like that. Although spending the whole day with all those kids must affect something.
yeah, I suppose I was a little mischiefious. (just from being bored in school)

this time I really wasn't though I really did want to know the answer.

I did tend to ask questions a lot though

like if my school's mascot (and namesake) was a union general, then why were our school colors the confederate colors?

Well, there's no such thing as a solid in the true sense of the word, really. Even the most dense, heavy, solid objects aren't stuck together at the molecular level. They may be close together, but they are seperate from one another. They just move slower.
All "solid" really means is that the molecules don't move so much due to a lack of energy. But when energy is applied, those molecules start moving, and that's how you get the motion of a solid object!

Atoms are not really solid, solid. There's a lot of space between them. What we actually consider solid is mostly empty space and we just feel the repulsion between billions of electromagnetic fields.

Again, by solid I meant solid on a macroscopic level. Anyway, what I don't get about the heat stuff is why the atoms vibrate. I mean, tie a string to two nails, then pull the middle (don't let go): Does it vibrate? No.

like if my school's mascot (and namesake) was a union general, then why were our school colors the confederate colors?
Lol, that must have gotten a few raised eyebrows :D

Lol, that must have gotten a few raised eyebrows :D
yeah, the ensuing conversation was quite funny and ended with me getting sent to the office (again) 3 weeks later I got that teacher fired (or better put, he did) and had to switch on the semester to the AP Physics class (which was why the teacher in the physics convo. was mad at me before we even started class)

US History conversation here (http://forums.jolt.co.uk/showpost.php?p=9999019&postcount=72) (not the one about the school colors though)

Again, by solid I meant solid on a macroscopic level. Anyway, what I don't get about the heat stuff is why the atoms vibrate. I mean, tie a string to two nails, then pull the middle (don't let go): Does it vibrate? No.Atoms aren't tied together by string though.
Try putting two balls together with a spring. And throw it out in space, you'll see it keeps vibrating. And since there is no friction in space it will go on doing so.
So in summary, the bond between atoms is more like a spring than string or a rod.

Again, by solid I meant solid on a macroscopic level. Anyway, what I don't get about the heat stuff is why the atoms vibrate. I mean, tie a string to two nails, then pull the middle (don't let go): Does it vibrate? No.
On a macroscopic level, no. At the atomic level, yes.

Think of a solid body as a beads curtain. Each bead is joined to the other with a piece of string which would be the electromagnetic force keeping the molecules together. However, the string isn't taunt, and the beads can move just a little each way. That's how they vibrate, the beads rattle but the curtain doesn't break. If you apply heat, they start to vibrate faster and further until the string brakes and that's when the solid becomes a liquid.

When you take heat away the beads move more slowly, until they stop moving at all at absolute zero.

EDIT: Yeah, Damor is right. Instead of imagining the beads joined with string that's not taunt, imagine them joined by springs.

When you apply forces to real objects, they will deform. this requires energy and because it is a real object, a part of that energy will be 'lost' to internal friction, etc. (this basicly is saying that entropy increases) and the object will heat up (a bit).

Atoms aren't tied together by string though.
Try putting two balls together with a spring. And throw it out in space, you'll see it keeps vibrating. And since there is no friction in space it will go on doing so.
So in summary, the bond between atoms is more like a spring than string or a rod.

I think you misunderstand: Normally the string tends to follow the shortest path between the two nails. When you pull it from a point in the middle, you add a third vertex but the string gains tension and wants to go back to the previous state. So when you let go, the point you pulled will shoot to its old position but go too fast and move too much, slow down, go back... Well, vibrate. But if you never let go of the string, it will not vibrate.

Doesn't the same thing happen with atoms? (To be sure, I suppose it's more the atoms in the second row not wanting the ones in the first to be pushed on them, but...)

I think you misunderstand: Normally the string tends to follow the shortest path between the two nails. When you pull it from a point in the middle, you add a third vertex but the string gains tension and wants to go back to the previous state. So when you let go, the point you pulled will shoot to its old position but go too fast and move too much, slow down, go back... Well, vibrate. But if you never let go of the string, it will not vibrate.The string as a whole won't, but the molecules/atoms inside do. But they do not vibrate in the same direction, or even necessarily at the same frequency. It's pretty much random, and considering the scale, that creates an appearance of rest at the macroscopic level.

Doesn't the same thing happen with atoms? (To be sure, I suppose it's more the atoms in the second row not wanting the ones in the first to be pushed on them, but...)There's nothing holding the atoms still. Like your example where you hold the string under tension. They just bump into each other chaotically.

I'm surprised no one really refuted what I said. I haven't taken a science in 4 years, and even then it was basic biology. :-p

If the difference (in H2O) between it being a solid, a liquid and a gas are how close together the molecules are (solid=close, gas=far)
Erm... the molecules are farther apart in ice - that's why it floats in water.

I think you misunderstand: Normally the string tends to follow the shortest path between the two nails. When you pull it from a point in the middle, you add a third vertex but the string gains tension and wants to go back to the previous state. So when you let go, the point you pulled will shoot to its old position but go too fast and move too much, slow down, go back... Well, vibrate. But if you never let go of the string, it will not vibrate.

Doesn't the same thing happen with atoms? (To be sure, I suppose it's more the atoms in the second row not wanting the ones in the first to be pushed on them, but...)
I think I understand what you mean. In the case of the vibrating piece of string, there are two vibrations going on: the one that you can see at the macro level, and the atomic one, that you can't see. In the first one all the atoms move pretty much together in the same direction until friction and whatnot stops them, but at the same time, in a much smaller scale, they're also moving themselves. Like a fly trapped in a jar in a car. The fly moves along with the car, and at the same time it flies around inside the jar.

I don't know if my analogies are any good, but they sure keep coming. Like pigs to a sty.

Erm... the molecules are farther apart in ice - that's why it floats in water.
Although water is an exception, and it has to do with the shape of the water molecule. While it's getting cold, the molecules start getting closer, until around 2C, when they start aligning like soldiers in a parade and this makes them occupy more space.

Most molecules don't behave like this and actually use less space when aligned than when randomly distributed.

Don't feel bad, I'm not to good with all the rules of Physics.

Although water is an exception, and it has to do with the shape of the water molecule. While it's getting cold, the molecules start getting closer, until around 2C, when they start aligning like soldiers in a parade and this makes them occupy more space.

Most molecules don't behave like this and actually use less space when aligned than when randomly distributed.
Yup. Water is the only substance known to man where its solid form will float in its liquid form. And a damn good thing too - if it sunk, we'd be screwed. Plants would get crushed/die and the ocean floor would be wiped out each time it got too cold out, deoxidizing our oceans and effectively stopping an essential cycle for life.

Erm... the molecules are farther apart in ice - that's why it floats in water.
really? (http://www.nyu.edu/pages/mathmol/textbook/slg.html)

hmm..........