# Sensei

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13

1. ## what is time ??

If your ruler is metallic, when we will be measuring distance at -100 C, 0 C, +100 C, +1000 C its length will be different, as metal shrinks and extends depending on temperature of environment. This effect is used in typical Mercury thermometer.
2. ## Ideas for a side game to play on SFN.

Somebody ideate a number. Other players have to find out what is this number. Player post his number and original author can answer only "higher", "lower" or "equal" - game is done and we know winner. To not cheat original author has to make photo of his number with monitor in background open with SFN thread visible so we can verify date. If allowed number is between 0...1000 number should be found after just 9-10 answers, if you know proper algorithm how to play it

5. ## Is Coulumb's Law, Symmetrical????

And we can see traces leaved by them in Cloud Chamber. Long thin traces are from beta particles (electron or positron). Short thick traces are from alpha particles. The more kinetic energy has particle, the longer trace.
6. ## Is Coulumb's Law, Symmetrical????

No. Just electron. Aluminum atom has 49218 times more mass than electron. Copper atom has 117667 times more mass than electron. Gold atom has 359109 times more mass than electron. When electron flows through conductor it sometimes hits atom, losing a bit of its kinetic energy, and heating atom, which is receiving electron's kinetic energy. The less this happens (lower resistance), the better conductor. If we have atom which lacks electron (ion+), and atom which has more electrons (ion-), the one that has more can give electron to the one which lack it. In batteries that have 1400 mAh on negative electrode we have 5000 Coulombs = 5000*6.24*10^18 = 3.12*10^22 electrons, and on positive electrode there are positive ions in the same quantity, which lacks electrons. After closing circuit electrons flow from negative electrode to positive electrode. Positive ions are attracting electrons. Each electron will have kinetic energy that corresponds to voltage difference. f.e. if voltage is 1 V, single electron will have 1 eV kinetic energy (electron volt unit). if voltage is 3.5 V, electron will have 3.5 eV kinetic energy. E=h*c/wavelength so wavelength = h*c/E = 4.135667*10^-15 * 299792458 / 3.5 = 354 nm UV LED have voltage drop 3.2-3.5 V (a bit is probably lost). So they emit photons with energies 3.2-3.5 eV, which correspond to wavelengths 387 nm .. 354 nm. Photon in ultraviolet spectrum. Where did you get such conclusions? I said "If you have single electron, charge Q will be -1.602*10^-19 C. If you have single proton, charge Q will be +1.602*10^-19 C." One has positive, other negative.
7. ## Help my understand why my cell phone charger current quantification failed!

2.1 A * 3600s = 7560 C. 7560 C / 2.1 C/s = 3600 s = 1 hour to charge to full with 2.1 A current. Is it plausible estimated time (assuming you don't play game at the same time ) ? Amper hour unit Ah is simply 3600 Coulombs. 1 Coulomb is 6.24*10^18 electrons. That's no surprise. After all it's more electrons per second. 1 A is 6.24*10^18 electrons, 2.1 A is 1.31*10^19 electrons per second. Apparently these games are using more energy than charger is able to provide. I guess so, heavy 3d. Do you have app showing cpu/gpu percentage usage with history.. ? Perhaps some application running all the time in background that's eating energy? Also loading a lot data to memory might have such effect. Typical computer random access memory must be refreshed periodically by current to sustain content. I had one Nokia 10 years ago that ate power like crazy when it was full of data. After deleting everything it could work several times longer. Current ebook technology is using screens that use power only while changing display. Games changes display even 30 FPS. Not sure whether such screens are used by some mobile phone. Might be highly model dependent.
8. ## Is Coulumb's Law, Symmetrical????

Q in Coulombs [C] is charge. It's kinda like quantity of particles. 1 C = 6.24*10^18 electrons. If you have single electron, charge Q will be -1.602*10^-19 C. If you have single proton, charge Q will be +1.602*10^-19 C. Electrons and electrons repel. Protons and protons repel. Electrons and protons attract. So, if you have Q1=-1 C and Q2=-1 C, after multiplication negative by negative, we will receive positive value. F=k*-1 C * -1 C / r^2 = k*1*1/r^2 If Q1=+1 C and Q2=+1 C F=k*1*1/r^2 effect will be the same. You can see how it works using electroscope. http://en.wikipedia.org/wiki/Electroscope "leafs" are free to move. The higher quantity of electrons will gather on them, the further leafs will be from each other.
9. ## Help my understand why my cell phone charger current quantification failed!

Imagine you have discharged cell phone battery to null. How long it takes you to charge it to 100% full again? If your cell phone battery has 1000 mAh, and loading current would be 2.1 A, it would charge to full in just 500 seconds = 8 min 20 sec (let's assume no loses). With 0.2 A, it would be 80 mins+. Mine cell phone battery has 3.7 V and 3.7 Wh on its back. Which is 1000 mAh. How could you do it? Typical voltage meter has as largest resistance as possible, usually a few mega ohms AFAIK. And ampere meter has the smallest resistance as possible. http://www.allaboutcircuits.com/vol_1/chpt_8/5.html

11. ## Wiring a DC motor

I plugged DC motor (from old cassette Walkman or so) to 5.5 V 4 AA batteries that I had at hand. Without anything Ampere meter is showing 2.4 A. With DC motor Ampere meter is showing 0.210 A, voltage drop on DC motor is 1.5 V (4 V remaining). With DC motor and 210 ohm resistor, 0 A, and motor doesn't want to run. With DC motor and 4.3 ohm resistor, 0.19 A, voltage drop 1.5 V. Motor runs but slightly slower than without resistor.
12. ## logarithm

log10 ( 10 ) = 1, because 10^1=10 log10 ( 100 ) = 2, because 10^2=100 log10 ( 1000 ) = 3, because 10^3=1000 etc. log2 ( 2 ) = 1, because 2^1=2 log2 ( 16 ) = 4, because 2^4=16 log2 ( 256 ) = 8, because 2^8=256 etc. Common bases: ln(x) = loge(x), base is e log(x) = log10(x), base is 10 In your example, if base is 5, then log5(125)=3
13. ## Renewable Energy Source Quantum Leap- Solar Panel in Space

Problem will be when the all people of the world will use more energy than Sun produces per day (and reaches our planet surface). And no more fossil or nuclear fuels will be available. But if all fossil fuels will be burned, air will have a lot of CO2 , which can be taken back by algae, or other vegetables. I have suspicion that you have no idea what is electromagnetic radiation.. This sounds like saying "Nicholas Kang invented sun, stars and light"..
14. ## Renewable Energy Source Quantum Leap- Solar Panel in Space

What "current energy crisis"? Renewable energy sources are introduced to reduce CO2 production to atmosphere, not because there is not enough energy. Actually everybody wastes a lot of energy. On transmission to client. On transformation from high voltage to low voltage (and vice versa). See how hot are electronic devices. They should/could have ambient temperature. In true crisis, everybody will be paying attention to every kW of energy used, buying devices that use as less as possible energy. In true crisis, everybody will have their own solar panels. Couple floor building have a lot of space to cover it by solar panels from all sides, and produce much more energy than the all people who live inside are using. But it would be bankruptcy of power station business. Have you idea how to transfer energy from orbit to Earth surface to actually use it?
15. ## physics of a motorbike collision - why it is so hazardous?

When bike or car accelerates to certain speed, all its particles have uniform velocity. Once bike or car hits something and decelerates, driver or passengers maintain velocity that they had before accident, as they are not permanently attached to bike/car. As a result they fly in air (in motorbike case), or smashes on front seats or window (in car case). I have made simple animation for you to illustrate it. At the beginning all parts of stick have equal velocity. After hit, top part of stick is decelerated, but middle and bottom still have previous velocity. In extreme situation stick could even be partitioned. In simpler case, it's starting spinning. Actually it's very easy. Attach particle to different parts of object. Particle has position x,y,z velocity x,y,z acceleration ax,ay,az And during animation particle is moved to new location frame by frame (or for more precision sub-frames like f.e. 1/1000 of second). Collision routine is checking whether something exist or not in new location. Movement is accepted when there is nothing in new location. If no movement can be performed (collision), there is needed to calculate new velocity/acceleration. The more particles is calculated, the slower simulation, but the more realistic is effect. Every modern 3d game is using this technique. Rapid deceleration of body while head still maintain velocity (or vice versa) will cause break of neck. Two weeks ago I read in newspaper about women who literally lost head during such accident (ripped of from the rest of body).
16. ## The Ultimatum: Mining the Sun? Yes, I am not Kidding

Surface of Earth is all day bombarded by protons from the Sun. So actually Sun is by itself sending its components all the time, without us having to fly for it. http://en.wikipedia.org/wiki/Solar_proton_event

20. ## Radioactive decay and information (split from what is real in physics)

In application I have functions: double get_isotope_mass( int protons, int neutrons ); // read isotope database and return mass in units double get_isotope_energy( int protons, int neutrons ); // call above, multiply by 931.494 MeV etc. return energy in [eV] double get_nucleus_energy( int protons, int neutrons ); // call above, and subtract electrons energy (protons * 0.5109989). return energy in [eV] All other code is only using get_nucleus_energy(). I wrote application, to not have to worry about calcs. Simply enter protons,neutrons quantity and app is displaying what are possible decay modes and Decay Energy. For instance decay of Plutonium-239 is prohibited in all modes but alpha decay, alpha decay energy 5.24454 MeV does match article http://en.wikipedia.org/wiki/Plutonium-239
21. ## Radioactive decay and information (split from what is real in physics)

Not only. Proton emission also, double proton emission. It's easy to make mistake that will remain unnoticed if we will be doing such shortcuts. (in above example one electron and one proton will be free)
22. ## Radio Waves As Fast As Light (Teleportation Theory)

I don't know about what book you're talking about. Certainly I didn't read it. I think so it's too late. If discussion will be progressing mods will split it to other thread. I see no problem. So, what is explanation of refractive index in your country.. ?
23. ## how to attain best weakforce and bigbang data

Refractive Indexes are measured for specific wavelength/frequency of laser (or light in old times). Especially in gases it's even worser- there has to be taken into account also temperature and pressure. On wikipedia RI article there is also mentioned that RI changes with density of glass. For instance we have data RI=1.33 for f.e. 532 nm, RI=1.34 for f.e. 650 nm, RI=1.32 for f.e. 405 nm, then RI is obviously not constant. Different value of RI for different light wavelength/frequency. You said "Refraction is only a problem if the index isn't constant," And I am asking which material fulfills your RI constancy for lights with as largest range of frequencies as possible (preferably not just visible spectrum).. ?
24. ## how to attain best weakforce and bigbang data

Which material has uniform refraction index in f.e. frequencies from 1 Hz to Compton Frequency?
25. ## Radioactive decay and information (split from what is real in physics)

Do you know how to calculate Decay Energy of unstable radioactive isotope? First, find parent isotope mass. They're in f.e. wikipedia articles such as http://en.wikipedia.org/wiki/Isotopes_of_hydrogen (last portion of link is name of element). For instance Carbon-14 has 14.0032419894 u Then, you need to multiply it by 1u = 931.494 MeV to receive total energy of nucleus + electrons. Then you need to get rid of mass-energy of electrons. Multiplying 0.510999 MeV by quantity of protons/electrons. Subtract total energy of electrons from energy of isotope. Repeat it for daughter isotope. In Carbon-14 case it's Nitrogen-14. Subtract N-14 nucleus energy from C-14 nucleus energy. Subtract electron energy (it's emitted during decay together with antineutrino) Result will be Decay Energy of isotope (kinetic energy of particles + energy of neutrino in our case). Decay Energy must be positive value. If you will calculate Decay Energy from stable isotope such as Deuterium, Helium-3, Helium-4 for all possible decay modes you will see that D.E. would be negative value. Thus these particles are stable. For Carbon-14 it's 0.156 MeV. As you can see this value does match article: http://en.wikipedia.org/wiki/Carbon-14 Other examples: Fusion of proton-proton, decay of carbon-11 and decay of Mangan-54: I wrote computer application which has built-in database of isotopes and calculates possible decay modes and released energy.
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