# Tag Info

54

The balls are entering the water well below the surface. The pressure there is much higher than at the surface. The work needed to push the balls into the water at this depth cancels the work gained when they float back up. We can ignore the gravitational force on the balls since gravity pulls down as much as up as you traverse the loop. Mathematically, ...

50

[5/3 - Extended the answer, made some corrections, and responded to John Duffield's comment] This is actually the paradox that led Einstein to General Relativity. Consider a special case: An electron and positron are at the Earth's surface. Bring them together and they annihilate, creating gamma rays (which is very energetic light). The gamma rays travel up ...

34

If the magnet is powerful enough to pull the ball up from the bottom of the ramp, the force on it will be quite strong at the top of the ramp. If so, why would the ball drop through the hole? The pull from the magnet will overwhelm gravity. Even if you constructed one where the ball could fall through the upper hole, I don't see any reason why it should ...

30

A simple symmetry argument might help here. Try to abstract everything away from your picture that is just a distraction. In the end it might look like this: Why should this move to the left or to the right? It cannot and therefore adding a person and wheels does not change the problem.

21

If gas A and gas B are of different density, then the situation sketched is not in equilibrium: the water level on the side of the light gas will be higher. There, the containers are moving down, and you have to push your containers through this net difference in level. You do need to put in energy here, which is probably the piece that you are trying to ...

20

Your guess at the solution to this paradox is correct. "Pumping energy up" to the space station, regardless of the method you choose, would require an input of at least the amount of energy you would gain in kinetic energy on the way down. This is just a variation on the impossible perpetual motion machine concept. In practice, you would not only not gain ...

15

If you could take from orbital energy, then it would decrease, until at some point in the future it would zero. Hence, it can't be perpetual.

15

I have reconstructed your diagram computationally and numerically computed the potential energy as a function of the orientation of the ring: As you can see, when we neglect friction (something that you can't do in the real world) the machine is indeed capable of perpetual motion. However, some important points: The total change in energy of the system ...

13

The energy needed to submerge a ball is equal to the energy gain from other ball to emerge from the water on the other side, so any waste on friction drives the process impossible.

13

The energy conservation law is compatible with every single observation we have made inside the Milky Way in science, or outside science, so the empirical evidence in favor of it is overwhelming, diverse, and universal. Theoretically, the case is also clear. Emmy Noether demonstrated that conservation laws are linked to symmetries. The validity of the ...

12

"Nature, to be commanded, must be obeyed". If perpetual motion is impossible in principle, no technology, no matter how advanced, will make it possible. By the way, perpetual is longer than any long period of time.

11

We already harvest energy from the Moon. It causes the tides and stress and strain and motion throughout the Earth. As a result, the Moon keeps getting farther away. (And it causes some heating in the Earth). The Moon at one time had a spin that was not locked to the Earth, and the tidal bulges in the Moon's shape caused by the Earth generated heat in the ...

10

What a beautiful machine! It is obviously radiating away energy, because it is loud. I actually have a similar machine at my house. It is also a high-Q mechanical resonator with a very narrow frequency acceptance; I have compared it to standard frequency references and I believe its stability is $\Delta f/f \approx 1\times 10^{-4}$. Here's a photo of it: ...

10

You do not need to invoke friction. The magnetic forces are in equilibrium by themselves so if you place the magnets in that configuration, they will not spontaneously begin to move. The reason is that there is a corresponding force on the magnets when they are vertical that matches the ones you've already drawn. Let me make a simple model. First of all, ...

10

If I were designing the experiment I would make the inside surfaces of the ramp out of of mu metal to shield the ball once it falls in the hole, otherwise a strong magnet will be pulling it back up the lower incline. I would use an iron ball with a smooth glass coating to reduce friction I would use a glass upper ramp , again to reduce friction A judicious ...

9

Thermodynamics does not prevent the trapping of heat. Here are limitations that thermodynamics does impose on the energy balance of the Earth: The Earth's surface can not be (passively) warmed hotter than the temperature of the sun The Earth's surface can not be (passively) cooled colder than the temperature of space Those living on the Earth can not get ...

9

The second law holds on average for systems of any size, large or small. If you have an isolated contraption containing just a few atoms, and you run it through some procedure (maybe as simple as waiting 5 seconds, or maybe more complicated), there is some probability that the atoms will wind up in a lower-entropy configuration at the end of the procedure ...

9

Ignoring many of the limiting factors of this problem (like air and water resistance), this wouldn't do what you think it would because the screw driver would travel around Earth and come back to you from the opposite direction. When you catch it again, it would slow you down again by the same amount that throwing it sped you up. You'd come to a halt. So ...

8

The problem is in the seal. The amount of work to move the seal against the water pressure is the same amount of energy that is gained by the balls when they are pushed up by the water. Even if we remove the seal and we imagine a magic "one-way pass-through" wall, the ball would still need to displace the same volume of water as itself in order to get into ...

8

First of all, nantennas in general don't violate the second law of thermodynamics, so they are not perpetual motion machines of second kind. As long as the total entropy goes up, the second law is obeyed. In other variables, it really means that a part of the incoming heat has to heat the nantenna up but there may still be a lot of energy left for energy ...

6

I can only hypothesize that the extra energy is due to cooling of environment. As there is some input of energy, that would not contradict the second law of thermodynamics.

6

A (non-accelerated) permanent magnet doesn't produce electromagnetic radiation. It is surrounded by a magnetic field (just like a charge is surrounded by an electric field), but it does not radiate. Especially there's no energy leaving the magnet. Note that for energy flow (as in radiation) you need both an electric and magnetic field, because only then you'...

6

He's basically saying assume you have some complicated system of weights connect by pulleys, and each weight can be in only one of two states: up or down. But you can trade off which ones are up and down, for example you can make 3 light weights go up by having one heavy one go down, and there are many other moves like this you can do. Now his point is ...

6

I was surprised to see an effect that's actually real, and not a hidden motor or something like that. I believe this experiment can feasibly be repeated. The principles behind it make sense. The driving force comes from the density difference in the cup versus in the pipes. The cup has very few bubbles in it compared to the pipe. Why? Because: The ...

6

The argument is wrong. The flow rate that is observed when the hole is freely communicating with the atmosphere is not the same flow rate that will be observed when the two holes are connected with a tube. The reason is that the flow rate through a hole depends on the pressure differential across the hole - on one side there is a certain height of liquid ...

6

Perhaps a gravitational analogy will help? The positive charges are railway trucks on a circular track in a frictionless environment. The positive plate is the top of a hill and the negative plate is the bottom of the hill. Set the railway trucks moving The trucks going down the hill lose gravitational potential energy whilst there are trucks going up the ...

6

If there is friction (air resistance), that friction will extract energy from the spinning fan, thus slowing it to a stop. If you extract energy in any other way, you are also applying friction to the fan, again slowing it to a stop. In other words, yes you can extract energy from the fan, but no more than the rotational energy that the fan possesses: E=...

5

The left magnet is pulled forward, pulling the car behind it. The right magnet is pulled backward, pushing the car ahead of it via the rod that attaches it to the car. (The fact that the rod loops over the car and attaches to the back makes no difference.) If the rod is flexible, the car will move forward as the magnets move closer together, but only ...

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