Recent content by Zizy

  1. Z

    Motion cannot be created or destroyed

    Light has momentum equal to E/c. Problem with classic definition of momentum is that conservation of it is clearly not working when an object moves at a high speed. Usual definition for relativistic speed (= close enough to c) is p = m*gamma*v, where gamma is relativistic factor...
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    Biology and Physics? Biophysics, biomimetics ?

    Perhaps organic solar cells could be an interesting topic. Maybe explain solar spectrum and how our eye got adapted. Describe how does measuring process of some animals look like... there are quite many topics out there, all could be interesting or very boring.
  3. Z

    What is the resolution to the lighthouse paradox?

    Well, let's assume you send out just one pulse of photons (light up just for a moment, then turn off again)... then let's assume you sent 10^20 photons out. Flash, when you are observing it close to the origin, appears bright. Further you go out, darker it gets. After a certain amount of...
  4. Z

    If mass is constant, will an astronaut weigh the same on Moon ?

    Mass would be equal. Problem is how to measure it - you usually measure mass through forces and the force does change. If you compare the force of an unknown body and something with known mass, scales could show correct mass, be it on the moon or jupiter. One simple spring won't work tho.
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    MATLAB Creating a Water Rocket Simulator with Matlab

    Use bottles of carbonated drinks, (such as pepsi, coca cola, fanta etc)... these can withstand more pressure (than the bottle of non-carbonated drink). Max pressure is roughly 10 bars, before it gets blown apart. It also depends on the state of the bottle... if you use duct tape, you can get...
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    Could Graphene Become the Next Silicon?

    As this debate is going on, I think I need to add this... "Future Nanoelectronics May Face Obstacles" Umea University (Sweden) (09/08/08) http://www.info.umu.se/NYHETER/PressmeddelandeEng.aspx?id=3219 If findings are correct, graphene will not become the next silicon, regardless of its...
  7. Z

    Quantum Mechanics: Particle-Wave Duality

    About vectors - this is only different formalism of the same thing... It is impossible to perfectly predict trajectory of an electron, if you meant that with construction how electron moves. As for orbitals - these are just energy states... an electron can exist in states in between, but these...
  8. Z

    Engineering Most useful (spoken) language to learn for a Nuclear Engineer?

    I recommend French, German or Russian language. It depends which country suits you best. I think that Germany is the best to live in... EDIT: For communication only, I would pick Russian.
  9. Z

    How would you define head-on collision?

    Also, velocity vectors should point in the opposite directions and need to be nonzero.
  10. Z

    Couple of Physics Question dealing with momentum, force, etc

    Net force is zero if there is no friction. Well, ball feels the same force (assuming both events are on equal height, like I think it was meant)
  11. Z

    Why do ice cubes stick together?

    It is possible that they just keep close because of surface tension. You would require some force to drag them apart because of water between them, so cubes stick together in their local energy minimum.
  12. Z

    Programming: Self-Writing Code & Understanding Plain English

    Well its not very hard (but its not easy!) to make a program that reproduces itself or that adds predefined code to it (from other text files for instance) and things like that. However, it is not yet known how to make a program that intelligently modifies itself or adds its code in some...
  13. Z

    Do Excited Molecules Emit the Same Frequency They Absorb?

    Yes, No, Depends. 1 and 2) Electrons in atoms (or molecules, or bonds in molecules etc...) have discrete energy levels. If an electron jumps from one state to another it emits a photon with the same energy that is between those states. Absorbtion is mostly the same but in the opposite...
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    Finding an interception point?

    Seems right. You could simplify equation a bit if you require more speed when running your game.
  15. Z

    Finding an interception point?

    Length of a = v2*t, b=v1*t, this reduces problem to just one variable, t... if there exists some sensible solution of t (real, positive), this problem has a solution. Calculation of a and p is easy when you have t. (condition for having a solution for t is that v2^2 >= v1^2*(sin(fi))^2. However...
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