This is the catamaran in question, and in a separate article(on the same thing) that it can travel 3x as fast as the wind...  Under everything I understand about physics, this does not work, you can't get more energy out than you put in, then can anyone explain this?
29514
Recently a  set a record for sailing a wind-powered land vehicle directly down wind, and a speed faster than wind speed. Wikipedia has a  talking about it, but it doesn't explain exactly how it works.  I can imagine some configurations, but I don't get how a system could be set up to push forward with a tailwind (when the cart is moving slower than the wind) and push forward with a head wind (when the cart is moving faster than the wind).  Could someone help explain how this is possible?
33580
I was musing about electric motors after seeing one randomly on TV, and there's something I'm must be remembering incorrectly.  It's just a thought experiment, so I'm imagining some theoretical DC electric motor, with a constant RMS current/voltage feeding in, and some constant load on it causing it to spin at some constant rpm and produce some constant torque.  Since voltage x current = electrical power = motor's mechanical power, that's the cap on how much you can get out of the machine.   But I remember that the greater the difference in rotational speeds between the rotor and stator fields (slip?), the more force/torque will be exerted on the rotor.   So in the hypothetical, if the motor is doing its thing and is stable with the load, if you suddenly increased the frequency of the input voltage/current, that in my mind would result in suddenly increasing the difference in relative rotational speeds of the stator/rotor, meaning the stator would feel more force/torque on it, which would make it want to speed up and catch up to the stator field, speeding up the load.  But only frequency changed and not how much electrical energy is entering the device, so there's no way that's possible! So I MUST be wrong, I just don't see where the error in my thinking is...  What's wrong with my thinking, and what would actually happen if you increased the frequency like that?  (I'm not an electrical person by trade, so there's a limit to my knowledge of concepts/terminology.)  [EDIT: I failed to mention that by "frequency", I'm referring to how DC motors can be controlled with pulse width modulation, and those pulses go in at some frequency. Otherwise it wouldn't make sense to talk about "frequency" with direct motors]
6377
How it this possible? Even if the gif is fake, the Mythbusters did it and with a large sail it really moves forward. What is the explanation?
98760
This was explained to me many years ago, by a physics teacher, with the following analogy:  "If someone on the beach wants to reach someone else that is in the water, they will try to travel as much as they can on the beach and as little as possible on the water, because this way they will get there faster."  I'm paraphrasing of course, but this is as accurate as I recall it. This explanation makes no sense to me. Was he telling me the light knows where it is going? It wants to get there faster? It chooses a different direction? (No need to answer these questions, this was just me trying to understand the analogy.)  My attempts to clarify the issue were without success and many years later I still don't know.    Why does light change direction when it travels through glass?
2471
So I asked my science teacher how wind could feel colder than normal air when the particles would be moving faster than normal air particles, meaning that they would have more kinetic energy and a higher temperature. My teacher told me that the faster rate of particles hitting your body would mean that the heat would leave faster than in normal air, but I was confused as to why they would take energy.   Eventually, I figured out that the air particles have kinetic energy separate from their velocity and my teacher confirmed this. He also confirmed that the particles would vibrate in place while they are moving.  How is this possible, and how does the vibration dictate the heat transferred, and not the velocity?
13463
I've seen lots of answers here about the episode "Force of Nature". The episode is about scientists discovering that travelling at speeds greater than warp 5 destroys subspace. It's been stated a few times here on this website that voyager's nacelles are made in a way that negates this effect, and that the rotation of the nacelles has something to do with it. Is this actually canon, and if so, how does rotating the nacelles upwards fix the problem? The Enterprises all had nacelles that were angled up from the hull.
84696
There is a  being thrown out of a flask, literally hovering out of the container  My question is how detailed a physical explanation of this phenomenon we have?  Question: More precisely, if we used the best available mechanical physics simulator software, and we tried to simulate this behavior, would the software be able to reproduce the effect or not? My guess is not but I would like to know why not.  Or do we have to content ourselves only with handwaved explanations? I am from the school of thought that you don't understand physics until you have a reasonable certainty that you can reproduce the physics in a computer.
67437
Will a machine or a technique ever be possible that allows  in interplanetary space?  And I ask out of pure curiosity. I know there is the "Vomit Comet" that allows for a non-gravity 'simulation' (for lack of a better word) on Earth, and I was thinking about if there would be a way to reverse that and rather have gravity in space.    edit: Say I was building a space shuttle because I'm dying to go to the moon (true story). Unlimited budget, the smartest people you can fathom helping me build my space shuttle.  I get motion sickness and the whole "anti-gravity" thing wouldn't really work for me.  Would there be a way to have gravity on my space shuttle? Perhaps by using a type of machine or magnets or something of the like?
25092
Lets say that hypothetically we have a rocket with constant mass, and an engine providing a constant force. I understand that it is unrealistic to have a rocket of constant mass with a rocket engine that ejects mass to accelerate, however this simplifies the problem. As the rocket accelerates the force from the engine will be travelling at a larger speed, therefore increasing the power of the rocket engine, since $W=Fm$, and this makes sense due to the constant acceleration that would occur with a constant force, since $E=\frac{1}{2}mv^2$. The rate of fuel flow into the engine will remain constant, so the chemical energy that is going into the engine will remain constant. This seems to contradict the increasing power from the force of the engine.
47567
I don't understand the fact that let's say hypothetically I was pushing a block on a frictionless surface, and I kept applying the same force on the object how it would keep accelerating! Wouldn't there have to be a certain velocity where it would stop getting faster? If not then what is actually acting on the object to cause it to accelerate infinitely?
114305
Theoretically, if I were to launch something faster than the speed of sound in water (around 5 times that of air), what would happen?
54473
Keeping it simple, what is the physics approach to a current in a wire connected to a battery? How does the electric field behave?  I've read somewhere that, contrary to the common conception, electrons don't really flow as water in a hose so, what is really going on there? How is energy transported at the speed of light if electrons don't flow like very fast water?
36899
how is this possible? I know there is some trick, should someone please explain?!
68782
So I was thinking... If heat I feel is just lots of particles going wild and transferring their energy to other bodies, why am I not burned by the wind?  When I thought about it more I figured out that wind usually carries some humidity, and since particles of liquid are moving same speed as the wind, they are basically static relative to each other, so no energy is transferred between them (wind and water particles). And if that water sticks to my skin and wind blows, it'll evaporate thus taking energy from my skin and make me feel cold.  Thing is, I don't think that's really the case but even if it is, if I somehow dry out the wind, will it burn me if it's strong enough? And winds can reach some pretty high velocities (though I must admit I'm not sure if they are comparable to movement of atoms in warm bodies etc...).  So. Bottom line. Can I be burned by wind in some perfect scenario?
53040
Recently, there was some news that said that the researchers at NASA have come across some impossible kind of space engine which does not require any fuel. I have read at a few places like ,  and . They all say that this engine seems to violate the laws of physics including conservation of momentum.  The original paper is .  Is the statement that it violates conservation of momentum true?
58057
The  is a proposed propulsion mechanism for spacecraft in which some form of microwave device provides the propulsion. The consensus from the physics community, including many voices on this site, is that the proposed device would violate conservation of momentum.   Several experiments have been conducted, by three main groups: (i) , from Satellite Propulsion Research Ltd, (ii) a research group at the Northwestern Polytechnical University in Xi'an, China, and (iii) Eagleworks Laboratories at NASA's Lyndon B. Johnson Space Center in Houston, Texas. However, few of these experiments have been performed in vacuum (and none of the vacuum tests has been published in a peer-reviewed journal), which means the effect of air currents around the device cannot be ruled out.  This device has been the subject of many questions on this site, including          and their many closed duplicates.  Many of these questions ask what the proposed explanations are, but then veer off into territory of the form "assuming it is true, how does it work?", so they have been (rightfully) closed as counterfactual physics. I feel this sort of bundling does a lot of harm to the discussion, and there is some scope to ask what exactly is being proposed as an explanation. So:     What do the proponents of EmDrive claim is the theoretical justification of the device's function?   Please limit answers exclusively to references, and indicate whether they are peer-reviewed or not. Please limit answers to serious attempts at explanations, as opposed to vague claims about the 'quantum vacuum' - or indicate if an experimental paper does not have any such theoretical explanation or reference.  To be clear, this is not the place to discuss whether the explanations are correct or not. If you have specific questions about any of these sources, ask it separately. (However, if your question starts with "assuming that this works", be prepared for it to be closed.) If you feel there are not enough resources on this thread, you can  but please do not post another question asking people to look for more references.
48047
See below gif image taken from .    Or see  about 30 sec in.    Is this a real effect?  Why does it seem to turn periodically? Can it be explained by classical mechanics alone? Is there a simple equation that models this behaviour?