thedarkshade

by the equations:

fS = μsR

fK = μKR

 

why μK < μs ?

I think it's the other way around actually! The coefficient of kinetic friction is BIGGER than static friction. Because with the increase on friction coefficient the body starts moving. The bigger the coefficient the faster movement!

I would want if you guys can tell me whyand how do forces occur??

Thanks:doh:

My definition of force is "a change in inertial state"! Because bodies are in inertial state when nothing acts on them, so a change on that state is actually a force!

And yet an easier definition of force (on a book I've read) is "force is a push or a pull"! And they're physicists who wrote that!

Now lets assume that there is a resulting force from this "explosion" into which sporadic brane collisions insert energy.This energy would not be inserted uniformally, and would allow the creation of matter.

How could "that energy" not be inserted uniformally when there was nothing that could prevent this energy be inserted uniformally? Before universe and now outside universe there is a matterless friction state!

We were discussing about magnesium last class and its reactions with water. And what I found interesting is that when the water is cold, it forms magnesium oxide, but when the water is hot (near boiling temperature) then it forms magnesium hydroxide. These are the reactions:

Mg + H20 --> MgO +H2 (cold water)

Mg + 2H2O --> Mg(OH)2 + H2 (hot water)

Interesting! WHY DOES THIS HAPPEN? WHAT CAUSES IT?

Thnx iNow, that really helped!

just like the gap would increase if car 1 was stationary and car 2 was going 30 mph.

Yeah, huh dummy huh!!! . thnx

electrons have mass.

I know they have mass and that their mass is 1836 smaller than proton's mass, but I'm very sure that I heard (in a science video) saying "electrons move at the full speed of light", in some particular occasion!

I'll get you the link as soon as I find it!

no, the gap will increase though there is no acceleration.

How come it's done that way???

It is quite hard to understand, this is how i see it. If on car is travelling at 70 mph and another is travelling at 100mph the first car is accellerating away from the second.

No, neither is accelerating or decelerating! They'll just keep moving maintaining the same distance from each other (of course, as long as the velocity is constant!)

according to relativity you CANNOT reach the speed of light.

.

Even bodies without rest mass can't reach the speed of light, can they?

What about when a star's core runs out of hydrogen? And then what about neutron stars? I think I've, in these cases the electrons orbit at THE FULL SPEED OF LIGHT!

Possible???

I think what we have to deal with here is called "active transport" (at least we call it that way!)

When our muscles are in rest, the level of Na is 10 times bigger outside than inside, and the level of K is 10 times bigger inside than outside. So according to physical laws, Na must move in inside until the balance is reached, and also K must move outside until the balanced is reached too. But here is a specific case that act some stuff called "Na and K pomps". Na pomp prevents Na to enter inside, and K pomp prevents K to go outside. So it acts from the place with less concentration to a place with higher concentration, and of course this does not occur spontaneously so energy is needed. And this energy is ATP (adenozim tria-phosphate), and it consumes quiet a lot energy. 20% of our entire body energy is consumed only by this "active transport"

It is also called active process because despite diffusion and osmosis (which need no energy), this needs energy to happen!

How can a light year = distance light travels in a year, if time stops at light speed according to relativity? Surely light could travel 2 lightyears in an instant if it wants...

It's hard to follow! Could you explain better your question please?

I know this might look silly to some people in here (as there are lots of more important subjects to discuss) what I'm gonna ask, but I really need to figure out how these things work! We've been dealing with some complicated (for me:doh: ) equations lately (like H2O2+KMnO4+H2SO4--> ...), and I just can't figure out how to equalize them using oxidation numbers (as our professor said it is easy to equalize by using oxidation number when the equations are tricky).

Could anyone please use any examples of equalizing equations using oxidation numbers and explain them?!

I really got to learn them!!!

Ooooh, come guys, this thing is really important to me! Any hint would be just fine!

Pleasee!

for example this equation.

5H2O2 + 2KMnO4 + 3H2SO4--> K2SO4 + 2MnSO4 +O2 + 8H2O

I know that both sides now are equal, but I just want to know to know how can we do this by using oxidation numbers!

I'm very interested to know. Any clue??

Light bends a little when it goes around a sharp corner.

And as the others said, the shadow with the true shape of the leaf will be if the leaf is on the ground, and the shadow will continue fuzz if the leaf is above the ground. This is because as light bends near sharp edges and that bend will go on and will be more apparent if the distance of the leaf (in this case) from the ground is higher, making so the shadow of the leaf less like the true form of the leaf.

I think that there are quiet e few factors that influence on a persons' personality and we all got to admit that no matter if people belong or not the same social class the difference between them is big. Different IQs, different marks, different interests, different hobbies are some things that make people differ from each other.

I also agree that genetic informations is the regulator of everything in our organism, so our mental capacities too. After all, I guess they're God's design.

But these mental capacities have to be developed in a proper way, otherwise these capacities will gradually become impotent (talent fades away), so the level of education matter too, because after all this is the stage when intellectual skills show up.

But another very important factor is also interest. Some people are interested more in exact sciences and some other in fine arts, while some other in social sciences. And people who are interested in art, it's hard for them to cope scientific theories and physical laws and other things related to science. Even if you get Eduard Witter to lecture them physics they will still not understand a damn think about physics and the other thing around too.

I do agree with you blue_cristal that genetic code, upbringing and educational level are the three key factors that influence ones intellectual capacities. But putting a percentage between these two would be quiet hard, because different percentages of these three give different kind of people with different mental capacities.

3/metallic bonds are looser than ionic bonds.

Thanks a lot insane_alien.

I was discussing with a friend of mine about metallic and ionic bonds and he started to get a little freaky about it. Sodium is malleable because of metallic bonds (thnx!), but this malleability causes only dislocation of structural nets, giving them the shape we want, but still these metallic bonds don't get "cut off", they still remain, right?

My friend is quiet sure that they break.

We've been having few lessons and experiments at school that have to do with alkali metals. Those HUGE explosions (especially K and Cs) in reacting with water make you think about them. But there are a few things I can't figure out, and I'd appreciate any help possible in my following questions?

1. Why are alkali metals so reactive?

2. Why can't you touch Na with uncovered hand?

3.Why metallic sodium (Na) is soft and malleable, while NaCl is strong and frail?

I's REALLY appreciate some answers.

Sorry swansont, I mixed it up with the place where the first atomic test took place. I'm very very sure that it was said "10 time higher than normal", and it was Brian Greene who said that on a collection of videos of his Elegant Universe in youtube.

"If I ignore the laws of physics what happens if..." The question can have any answer you want

except anything that has to do with our physical reality!

Except in the case of light, where everything pretty much turns out okay.

Yeah, but it's OK only because those "conditions" are normal because it's light itself.

Xenon will form reasonably stable compounds though, as they get a little More reactive as we go down the group (the outer electrons are further away from the nucleus).

And this increase in reactivity is due to less nucleus influence on the outer electrons, right?

Because going down the groups the number of electrons keeps increasing and also new shells are added, so the distance of the outer electrons from nucleus is also increased! So the nucleus influence on these electrons keeps decreasing down the group, and they become more reactive and less stable, right?

Helium is an inter gas, so it needs extreme conditions to make it react. That is because its electronic configuration is completed (1s^2) and it normally doesn't react. Also the necessary energy to "take" an electron away from helium is huge, energy which reactions cannot provide, so it's normally stable element.

Like iNow said, there must be a REALLY REALLY BIG IF, but let's take into consideration that something has reached the speed of light, and ask what would it see? Well, as time dilation now becomes infinite, then first of all there would be no time at all . Then the mass is completely converted into energy or mass is now infinite. So what would it see? I really can't provide an answer (surely nobody can) to this, but as I was writting something came to my mind. What would you see if your getting into a black hole? there also is no time! And as when you reach the speed of light (which is impossible practically) everything gets tricky, then I guess the view would be QUIET DIFFERENT from our physical world!

"What happens if you follow a photon at the speed of light?" this a question that Einstein itself asked. And I agree that objects with rest mass cannot reach the speed of light, but according to Einstein's theory of Special Relativity they can reach 99% of it, and then the time dilation.

Anyway, I think that an answer has nowdays been provided to you and also to Einstein question. And that answer is "If you follow a photon at the speed of light, the photon moves away from you at the speed of light"

E=0??? That sounds kinda unphysical you know! After all, matter is energy and energy is matter, you can prove this by the same equation you used above (E=mc^2).Every single body that reaches the speed of light, it's matter is completely turned into energy, and it also has no time (only for outside observers as the time deviation goes infinite). So saying that E=0 is the same as just saying "no mass, no existence", and we know that photons exist.

It sounds kinda weird!!!

Hi Martin,

It might sound like stupid but I got this way of looking Big Bang from a different point of view! And there are some things that make me think tightly!

So at first there was nothing, just an infinitely dense point. Then there was this energy (dark energy) which made this point expand and accelerate! Normally, this energy should have been given uniformly to that point, so all its sides expand equally, and as it expanded (and expands) in frictionless conditions then it should go one forever.

But I always get stuck to the same think! If this energy (dark) is given uniformly so this dot expands equally to all its sides, then why aren't its sides completely the same? The couldn't possible be anything to make these sides change and so differ because there was nothing before!

And one more thing. Dark matter is just like a gum that acts between everything in the universe (stops them from getting all away). And if there comes a state when dark energy shall decrease, will then dark matter bring all the universe back to that infinitely dense point??

Strange huh?!

Thnc for ur help.