Physics

The 9/11 Massacre is quite known to everyone. I was wondering the mechanism behind the massive destruction. Is it the principle of Center of Mass?

i am doing cold fusion for a science fair project and i was wondering if any one has heard of a buildable cold fusion reactor, as i will try to build one as a experiment, but i havent founed any with concrete instructions to asemble one yet. does anyone have a idea on how to build one. thanks for you help.

On Earth, Which is possibly the most elastic material ?

Hi I wonder if you science guys can see if this works OK if you guys know that The maglev train moves on magnetic levitation but I wonder if this process can be reversed... in such a way. I was thinking that this method may make a lot of things faster.... like Tankers?

Hello quick question, Let's say there is tube with costant flow. It has ion channels surrouding it. X ion is absorbed from it, Y ion is secreted into it. When you increase flow rate does aborption of X decrease and secretion of Y increase. Is it because there is less time for reabsorption and more empty space for secretion. Just asking to clarify. Thanks

Protons and electrons are supposedly point particles surrounded by electrostatic fields. But in what sense do the particles themselves ever directly interact without intermediation by the force-fields that surround them? When atoms and molecules interact, it is the same-charge repulsion of their electrons that act as an interface for exchanged work, correct? The configuration of the electrons within the atoms is the result of their attraction to the nucleus by the positive charge of the protons, right, not any direct interaction of the particles? So within the physics that models matter as consisting of such "point-particles," I wonder what the basis is for assuming t…

What is the force called when your pulled towards a fast moving car. I have noticed whenever a car zooms past me going like 100 km/h it seems to almost drag me towards it. Can someone please explain. Thank you

I was wondering whether it would be possible to generalize about a relationship between gravity and atmospheric pressure in any gravity-well. I was trying to think of the parameters that would affect atmospheric pressure and came up with basically just the amount of heat driving the molecules and the amount of gravity compressing them. I also wondered if gravity helps determine pressure by how fast particles accelerate in free-fall, or if this is negligible because of their small mass. I wondered if there is maybe a layer of atmosphere in any gas-giant that corresponds with pressure at sea-level, and whether this would also correspond gravitationally due to the particu…

Since this seems like a Bohr-model type idea about electron behavior vis-a-vis the nucleus, I will pose it from a historical point of view. Has there ever been research that examined the relationship between electron density and repulsion within a given layer of electrons as radius from the nucleus would decrease? Specifically, it seems like repulsion among the electrons within the same radial sphere would increase as the radius of that sphere from the protons decreased. Since electron speed/momentum would be a consequence of greater electrostatic attraction from the protons; and it would correspond with greater repulsion among the electrons at the smaller radius, I wo…

Physical effects relating electric and magnetic properties have sometimes 'dual' analogues - with exchanged places. For example in Aharonov-Bohm effect, the phase of charged particle depends on side of magnetic flux tube it comes through, while in its 'dual' analogue: Aharonov-Casher, the particle has magnetic moment and tube contains line of charge (it was used e.g. for neutron interference). Another interesting 'dual' effect (hypothetical) can be found in magnetic monopole Wikipedia article - full expression for Lorenz force in such case would be: [math]\mathbf{F}=q_e\left(\mathbf{E}+\frac{\mathbf{v}}{c}\times \mathbf{B}\right)+q_m\left(\mathbf{B}- \frac{\mathbf{v}}{c…

So basically I posted the following analysis as a comment on this cat video on youtube. "At about 2 minutes in, the fan circles 4 times in 5 seconds. That's 0.8 cycles per second. If we assume the cat's spinning an average distance of a metre from the centre of the fan, that means it's moving at 2.5 metres per second. (v=2*pi*f*r) Also, the circular acceleration would be (v*v)/r, which would mean a velocity change of 6.25 metres per second every second. And so, to the cat, the pull of the rope probably feels like two thirds of the pull of gravity." What say you, Science Forums? Is my analysis valid?

First, imagine you have a perfectly rigid tower that extends from Earth to an altitude beyond geosynchronous orbital altitude. An elevator shaft in the center of the tower allows an elevator to travel up through the tower. As the elevator ascends, the force required to maintain constant speed decreases until it reaches geosynchronous altitude, where it remains stationary provided it is stopped and no further vertical force is added to it in either direction, right? Then, if it is moved to a higher altitude and stopped again, the force of the tower itself should work to push it upward (a sort of catapult effect), and this upward motion will be acceleration, right, since…

Hi, Something I pretty sure about was thrown into doubt this evening by some opinions outside this forum. I'm hoping someone can put me back on track and into my old comfort zone. What is the behaviour describing a perfect bouncing ball in a lossless system ... Now I know it's not true Simple Harmonic Motion (SHM) since we have at one end: the bouncea high-speed drop reaching maximum velocity an 'instantaneous' reversal of direction a high-speed climb starting at maximum velocity [*]the apex a slowing of the rate of climb from maximum velocity to 0 an 'instantaneous' reversal of direction an accelerating rate of fall from 0 to maximum velocity So we d…

Hello, I have a question. I need to know what does likelihood mean and what is the relation between it and chi-squared. I know they are almost inverse of each other, such that maximum likelihood is equal to minimum chi-squared, but I want to know what does exactly mean a 3-dimensional likelihood graph. Can someone explain it for me?

Note: I tried to post in the philosophy forum but it won't let me. If a moderator can redirect this post to the philosophy forum this would be great! The enjoyment of pleasure derived from basking in the meditative presence of an alluring beauty is perhaps one of the most emotionally salient peak moments of experiential life. And while it is a positivistic (good) hedonistic pleasure, it can also be a curse. Most of us are perhaps well aware of the biological and evolutionary reasons and explanations on how physical beauty and our perception of beauty evolved in tandem for both genders. Yet, understanding the underlying mechanisms of how such a process works…

Although i like to think i understand electromagnetic waves there is still something i don't understand: Why in the case of light waves do some substances not reflect any light out at all (such as glass), i know its because it doesn't 'absorb' the frequencies and therefor photons aren't released, but what is it exactly which causes it to be unaffected by the electromagnetic wave? In the same sense why doesn't all the radio waves and other waves shooting around us drastically effect our body?

ok, so im doing a science faire project on nuclear fusion but i dont undderstand how by combining 2 atoms the mass will be inferior to the initial mass and that their will be a creation of energy. thanks for your help. james

Hello reader, I personally do not believe in this dark matter and dark energy stuff. It is only the excepted idea as it has been forced upon us. No alternatives have been given as far as I know. I think it is a merely a mathematical convenience and see no real reason to believe it exists. I believe that something yet undiscovered that is the real DM/DE. No alternatives are ever discussed. If there are any will people please tell me about them below. If there are not will the people here please begin to think of possible alternatives. We constantly find new planets and stars. This could mean that a lot of this 'missing mass' is actually there. Maybe even all o…

IF the planets were molten when they were born spheres and the universe is expanding would the spheres not loot like teardrop shape due to the force of the expanding universe? Also, if the sun if a sphere and the universe is expanding would the sun not look like a teardrop shape too? If the universe is expanding why is this not true?

Heres an idea, up to at some highlands, have large lightning rods raised to the sky collecting lightning. Pass the current through a 1:10000000 ratio transformer fed into a capacitor the size of a house. wala! free CLEAN energy!!

Is anyone familiar with van der waals forces in plasma, and or maybe van der waals forces in general? I need some information on them and google has not been very helpful. any help would be appreciated

OK, ignore the magical space fairies. Also, apologies: this may be posted in the wrong area, but I'll be damned if I can find the right subforum for it. So, I was walking to a meeting early this morning and, while crossing a busy street to walk onto campus, I noticed something that I think I've seen before and forgotten about. On a cold and bright morning like this, my breath is visible. I have a reasonably informed understanding of why that is. Here's the thing, though: when crossing the street, it is much more visible. Dramatically so. I recalled that I've seen this in parking lots, around major streets, and anywhere around running cars. So, what is i…

? A clue, its got a t in it.

what happens if you keep on charging a capacior? will it just keep on building up charge? or reach a point where it can't charge any longer or explode or what?

We've just started tackling relativity in our physics class, and there's a thought experiment I've come up with that I can't seem to resolve. Say you have an empty infinite universe, and in that universe are two objects, A and B, which are moving at some velocity relative to each other. Since there are no reference points except for the two objects, from A's frame of reference it is B that is moving and A that is stationary and from B's frame the opposite, ie. A is moving and B is stationary. Since time dilates due to velocity, in A's frame of reference B's time will be slower and from B's frame of reference A's time will be slower. But that can't be, since it would mean …