swansont

I think i am going to just needed a temperature to energy (easiest way possible)... But i am not so sure about the equation that you gave me' date=' E =kT

 

I looked around on the internet and the closest i came to that equation was: E=(2/3)*k*T, maybe this includes the factor of 1/2 for each degree of freedom.

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Check again - that should be (3/2)kT

Can any body tell me the definition of technology?

dic·tion·ar·y n.

pl. dic·tion·ar·ies

A reference book containing an alphabetical list of words, with information given for each word, usually including meaning, pronunciation, and etymology.

If its any help' date=' the equation linking the two is as follows:

 

E = kT

 

E being energy in joules

k being boltzman's constant

T being temperature (rememebr to convert into Kelvin)[/quote']

 

There's a factor of 1/2 for each degree of freedom.

I dont, it can be said that physics is a subset of chemistry, but offcourse that depends on whether you a physict or chemist

I refer you to the words of Ernest Rutherford, winner of the 1908 Nobel Prize in chemistry: "All science is either physics or stamp collecting."

Subset of chemistry. Bah!

I think it shows deep insight and self awareness on the part of our US cousins. Either try to teach American schoolkids to spell properly (e.g. colour' date=' behaviour, haemglobin, foetus), or make the words easier to spell (color, behavior, hemaglobin, fetus).

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No, it was the "extra vowel" tax, without representation, that we were rebelling against.

any body?

Prompting people when they're offline doesn't do any good.

The object would accelerate vertically if the vertical component of the force is greater than the weight. But that information isn't in the diagram.

Black absorbes all light' date=' white reflects all light.

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There are no perfect absorbers or reflectors.

No' date=' black [i']is[/i] a colour. Colours are just labels.

 

What it isn't is a colour of light.

There are two distinctions to be made. Color as a frequency of light, or color as perceived by our eyes.

Neither white nor black is a frequency to be found in the spectrum. But neither is brown, or a number of other colors found in a crayon box or at the local home improvement/paint store. Those colors are how combinations of frequencies are perceived by our eyes.

well the whole idea of ' date=' if you travel faster than c theres moving backward in time.

So time must travel at "c" ?

So ya mean virtual particles dont nessecarily travel at the speed of light? (or above?)[/quote']

 

Time isn't an object, so saying it travels at c (or faster or slower) is nonsensical.

 

Not all virtual particles are massless. They are still constrained be the Heisenberg uncertainty principle, and the implication of that is that the massive virtual particles don't travel at c.

You mean all virtual particles. Why must they travel at the speed of light? or above?

 

Why does time travel at the speed of light? It may seem like a stupid question but i really dont know.

I don't think "all virtual particles" is right - lots of virtual particles are not ones with zero rest mass.

Particles with zero rest mass travel at c because that's the solution to the equations. Particles with rest mass travelling at either v<c or v>c are also solutions to the equations, but they are different solutions from each other. So tachyons, if they exist, can never travel slower than c.

What do you mean by 'time travelling at the speed of light'?

Ok' date=' Swansont, in ur previous message, the most confusing word is [b']"component", [/b] I dont get what u r talking about component in this case.......Can u explain it?

 

How can something doing not in the direction of force still can move a distance that is not in the direction?

in my case, the trolly is moving horizontally, but the force's direction is diagonal.....

A force that is at some angle is the same as the sum of two forces, one horizontal and the other vertical, and whose magnitude is given by the Pythagorean theorem if you were to draw the right triangle with the three vectors. The horizontal and vertical parts are the components. How big any given component is depends on the angle - you can use trig to figure that out.

In your example there are other forces present that are not named. Gravity, for instance, exerts a force downward. The upward component of the force the rope exerts acts against gravity, and makes no contribution to the forward motion. That component would be given by the sine of the angle (400N * sin30). The component of the forward force is given by the cosine (400N * cos30) (using the angle in your drawing)

(400*sin30)²+(400*cos30)²=400²

so you can see the component forces add (as vectors) to be the total force of 400N

Sorry Swansont' date=' I still dont get it, you say that a force that is perpendicular does no work, but [b']why you cannot do cos 90 then?[/b]

On the other hand, I know this is impossible because it is not in the direction of the force, but by that, if in my case(see in the picture of the 1st page in the thread), why we should do "cos"? we can just force times distance, because the distance is in the direction of the force................

The cosine tells you the component of the force doing the work. The perpendicular component doesn't contribute.

The last recorded flip was about 780' date='000 years ago

...

and by using carbon dating, geologists have determined...[/quote']

 

Given the time scale and that they aren't dating stuff that was once alive, Carbon dating would not be used. It's only useful out to 50k years or so, and only on organic material that takes in carbon from the atmosphere (i.e. CO₂).

Again' date=' [b']What i really confused is still about how does it (cosine) do to the direction of the forces and distance.........in the solution of work?[/b]

 

 

Any help?

The dot product, that gives you the cosine, tells you what the projection of the vectors are onto each other. i.e. how much of the force is in the same direction as the displacement. A force that is perpendicular to the displacement can't add or remove energy, thus it does no work. A force that is in the exact same direction as the displacement does the maximum work possible. The cosine, in essence, tells you how efficiently you are doing the work with that force.

Also keep in mind that the division between chemistry and physics was originally defined a long time ago. With more recent discoveries, there is overlap where there didn't used to be. Chemistry used to be about what happened when you mixed a bunch of chemicals together. Now e.g. with QM, the theory describes molecular bonds, so both physicists and chemists are going to study it. Just like you have biochemistry and biophysics, there's physical chemistry and nuclear chemistry and chemical physics.

You need to break the forces down into their x and y components. Only the net force in the x direction (horizontal) does any work for displacement in that direction. Any components in the y direction make no contribution.

Thx Dark' date=' the information is relavant and helpful.........

 

Anyway, I have also problems with the direction of forces.................

 

[b']Can anyone tell me the basic concepts of the direction of force?[/b] for eg, how can an object move diagonally? or move in an indefined route, since it makes even harder to measure the distance and to say the direction of the force.........

 

 

Aprciate for furthur helps!

The net force is always in the direction of the acceleration, but this doesn't mean that it has to be in the direction of the displacement (which is given by the velocity vector)

"Diagonal" motion is just an artifact of a coordinate system, which is arbitrary.

I want a G5

I've got one at work My G4 cube was neat looking, but needed to be replaced, and is now happily toiling as our fax server.

calculate the potential energy the bullet would have at an infinite distance' date=' and then caculate the velocity required to give the bullet an equal kinetic energy.

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Not quite. The PE at infinity is zero, using PE=-GMm/r. It's the mechanical energy that is zero at infinity, where ME=KE+PE

 

So you want to find the PE at the surface, and add an equal magnitude of KE.

Mac G4 dual 867 MHz, 1 GB RAM.

but what is the condition of e so that it loses mga of energy each bounce

e is the fraction of the original energy (measured above the first step, or mgH) that is retained. You should be able to set up a simple equation with that information.

If you want the bounce height relative to the stairs to be equal, then the ball has to lose the energy it gained in one step on each bounce. So if the height of a step is a, it loses mga of energy in each bounce.

on certain occasions this general phenomenon is surpassed in the form of a "sun dog" a rainbow around the Sun in a complete circle' date=' like a halo

a very beautifull but rare occurance in the UK, I`ve seen one only once on Shell Island in Wales, but many of them when I lived in Canada.

water falls will often have the same effect too in bright sunlight at certain angles.

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Also known as a 22 degree halo. It's caused by ice crystals in the upper atmosphere. I've seen a couple - yeah, they're pretty neat.

fyi, the longest wavelength of light is ~700nm (which is red).

There's not an absolute cutoff, though, so the choice is somewhat arbitrary for saying what the visible range is. The eye efficiency looks sorta gaussian, but a lot of the time a linear scale is shown, rather than a log scale, which makes it look like the efficiency goes to zero at 400nm and 700nm. I've used lasers at 780 nm and could see diffuse reflections at low power (a few mW). I've also seen 852 nm light (a few hundred mW source) which made me realize that I wasn't wearing my laser goggles.