# danny8522003

Senior Members

320

2. ## firefox technique

Why doesnt FF just include all the useful add ons?
3. ## Four states of matter

Screw it, here's list of them all http://en.wikipedia.org/wiki/List_of_phases_of_matter
4. ## Four states of matter

There's also a fifth state called Bose-Einstein condensate. http://en.wikipedia.org/wiki/Bose-Einstein_condensate
5. ## Some Questions About Light

As posted in the "mass" thread. Basically, anything with mass cannot b accelerated to the speed of light in a vacuum. Things like quarks can be accelerated to about 99.9% the speed of light but cannot reach it. Only particles with 0 rest mass can reach c.
6. ## gravitational acceleration

I agree with both of those values. Although, yourdadonapogo said use your value for v to find t. This is bad practice because your value for v might be incorrect, so try and use a equation to find another variable that doesnt contain one that you've had to calculate. Then there is less chance of you getting both the answers wrong .
7. ## gravitational acceleration

Ok, feel free to repost if you get stuck
8. ## gravitational acceleration

You can use Newtons Equations of motion for this as g has been given as a constant. List all the things you know: s (distance travelled) = 75,000m a (acceleration) = 9.79ms^-2 u (initial velocity) = 0 t (time) = ? v (final velocity) = ? Here are the equations: Equation 1 v = u + at Equation 2 s = ½(v + u)t Equation 3 s = ut + ½at² Equation 4 v² = u² + 2as Find one so that you input all the known values, but have one unknown and rearrange to find it. First find v, then find t. Hope that helps.
9. ## Life in the Undergrowth...

Very interesting
10. ## Ocular Networks

I get an error in my browser that says the data from the site is corrupted for some reason and i cant view the page. Using Opera 8.5
11. ## Elegant Universe Question

Yea, i dont understand how BOTH clocks can be slow. I think i vaguely understand it, using an anology used in the book. Don't think i was looking at it in a relativistic enough maner, thanks for the help! -------------------------------------- Although it seems as though both clocks would say 10pm and we'd both argue we were slower than each other, but i think i understand it now.
12. ## mass

Nah i know electrons do it too. Id hazard a guess that every 'elimentary' particle does.
13. ## Elegant Universe Question

I'm reading The Elegant Universe at the moment and it states that as people with clocks travel past each other at a significant constant velocity, they BOTH see each others clocks slow down. This makes complete sense in that everything is relative etc, but i dont see how BOTH can be correct. Hopefully one of the experts can clear this up for me . Cheers, Dan
14. ## mass

Think of Einsteins equation e=mc^2, this shows that energy is interchangable with matter. Therefore more energy, more mass. Rest mass gives the mass of an object if it had no energy, i.e. it is at rest. In this way the rest mass of a photon is zero. Using Einsteins we can see that photons have something called relativistic mass. Use hf=mc^2 to find this. Relativistic mass is an outdated term so we simply say that photons have no mass, they are just a 'clump' of energy. Again, using e=mc^2 we can see that as an object gains energy it's relativistic mass increases (hence why objects with mass cannot reach c because of the gain in kinetic energy it possesses as it gets faster). E = mc^2/sqrt(1 - v^2/c^2) shows that when v=c the equation has a 0 as the denominator, any fraction with a 0 at the bottom and a number >0 at the top equals infinity. This is why infinite energy is required to speed objects with rest mass up to c and is therefore impossible. If m = 0 we get a 0 at the top.
15. ## Could a black hole be inverted light?

No my figure is in grams for the mass of the sun and a typical black hole is 10 times that. You need two black holes which make 20. Since 1 gram of matter makes Hiroshima (according to 5614), you just divide by 1. So 7.95568 × 10^35 kilotonnes. Yeh?
16. ## Could a black hole be inverted light?

Yea so find the mass of the sun in grams, then multiply that by 20. That's how many Hiroshimas it would be equivtlent to. mass of the sun = 1.98892 × 10^33 grams x by 20 That's 3.97784 × 10^34 times the power of that nuke, ouch!
17. ## 70Hz kicks ass

I use NCH Tone Generator when i was trying to set up my sub, it might work well for trying to find those resonance frequencies.
18. ## Volume of Gases in a mixture

I dont see why not, just plug the numbers into [MATH]V=\frac{nRT}{P}[/MATH]

20. ## Massless particles

A very helpful explanation... http://math.ucr.edu/home/baez/physics/Relativity/SpeedOfLight/FTL.html#16
21. ## Escape Velocity of a Body

Ahh i see, makes sense now. Thank you.
22. ## Speed of gravity vs speed of light?

They are the four types of forces each with their own carrier particle that travels at c. I read that the carrier particle for EM force is the photon, not sure i understand why. Maybe someone can help?
23. ## Escape Velocity of a Body

But both the masses have gravitational fields that depend upon their mass. A pencil and a planet would attract each other a lot less than say a star and a planet, so why doesnt the escape velocity represent this?
24. ## Escape Velocity of a Body

Hey guys, I was doing gravitation today in physics and we were looking at escape velocities. The velocity is given by: [MATH]v = \sqrt\frac{2Gm}{x}[/MATH] Now this equation only has the value of one of the masses in, so the velocity is only dependant upon one mass. My question is why is this independant of the mass of the object trying to escape? If you were trying to jump off the Earth, you would attract the Earth and the Earth would attract you. Although if you had the mass of the moon your attractive force would be higher, so why does this not mean the velocity would need to be greater for the bodies to seperate compared to you having your mass or the mass of the moon? Everything is relative after all.
25. ## Speed of gravity vs speed of light?

If gravity happened instantaneously would this not have to travel faster than light? Seeing as no info can travel ftl this must be impossible.
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