- **الفيزياء العامة**
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- - **101 حقيقة في الفيزياء**
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101 حقيقة في الفيزياءاقرأ هذه الحقائق البسيطة في الفيزياء ، استخلص منها المصطلحات ، تأكد أنك تفهمها جيد ، دائما سيتم سؤالك عنها في الفيزياء ! Mechanics 1- Weight (force of gravity) decreases as you move away from the earth by distance squared. 2- Mass and inertia are the same thing. 3- Constant velocity and zero velocity means the net force is zero and acceleration is zero. 4- Weight (in newtons) is mass x acceleration (w = mg). Mass is not weight! 5- Velocity, displacement [s], momentum, force and acceleration are vectors. 6- Speed, distance [d], time, and energy (joules) are scalar quantities. 7- The slope of the velocity-time graph is acceleration. 8- At zero (0) degrees two vectors have a resultant equal to their sum. At 180 degrees two vectors have a resultant equal to their difference. From the difference to the sum is the total range of possible resultants. 9- Centripetal force and centripetal acceleration vectors are toward the center of the circle- while the velocity vector is tangent to the circle. 10- An unbalanced force (object not in equilibrium) must produce acceleration. 11- The slope of the distance-tine graph is velocity. 12- The equilibrant force is equal in magnitude but opposite in direction to the resultant vector. 13- Momentum is conserved in all collision systems. 14- Magnitude is a term use to state how large a vector quantity is. [عزيزى الزائر لايمكنك مشاهده الروابط الا بعد التسجيلللتسجيل اضغط هنا] |

Energy 15-Mechanical energy is the sum of the potential and kinetic energy. 16- Units: a = [m/sec2], F = [kg•m/sec2] (newton), work = pe= ke = [kg•m2/sec2] (joule) 17- An ev is an energy unit equal to 1.6 x 10-19 joules 18- Gravitational potential energy increases as height increases. 19- Kinetic energy changes only if velocity changes. 20- Mechanical energy (pe + ke) does not change for a free falling mass or a swinging pendulum. (when ignoring air friction) 21- The units for power are [joules/sec] or the rate of change of energy. |

Electricity 22- A coulomb is charge, an amp is current [coulomb/sec] and a volt is potential difference [joule/coulomb]. 23- Short fat cold wires make the best conductors. 24- Electrons and protons have equal amounts of charge (1.6 x 10-19 coulombs each). 25- Adding a resistor in parallel decreases the total resistance of a circuit. 26-Adding a resistor in series increases the total resistance of a circuit. 27- All resistors in series have equal current (I). 28- All resistors in parallel have equal voltage (V). 29- If two charged spheres touch each other add the charges and divide by two to find the final charge on each sphere. 30- Insulators contain no free electrons. 31- Ionized gases conduct electric current using positive ions, negative ions and electrons. 32- Electric fields all point in the direction of the force on a positive test charge. 33- Electric fields between two parallel plates are uniform in strength except at the edges. 34- Millikan determined the charge on a single electron using his famous oil-drop experiment. 35- All charge changes result from the movement of electrons not protons (an object becomes positive by losing electrons) |

Magnetism 36- The direction of a magnetic field is defined by the direction a compass needle points. 37- Magnetic fields point from the north to the south outside the magnet and south to north inside the magnet. 38- Magnetic flux is measured in webers. 39- Left hands are for negative charges and right hands are for positive charges. 40- The first hand rule deals with the B-field around a current bearing wire, the third hand rule looks at the force on charges moving in a B-field, and the second hand rule is redundant. 41- Solenoids are stronger with more current or more wire turns or adding a soft iron core. |

Wave Phenomena 42- Sound waves are longitudinal and mechanical. 43- Light slows down, bends toward the normal and has a shorter wavelength when it enters a higher (n) value medium. 44- All angles in wave theory problems are measured to the normal. 45- Blue light has more energy. A shorter wavelength and a higher frequency than red light (remember- ROYGBIV). 46- The electromagnetic spectrum (radio, infrared, visible. Ultraviolet x-ray and gamma) are listed lowest energy to highest. 47- A prism produces a rainbow from white light by dispersion (red bends the least because it slows the least). 48- Light wave are transverse (they can be polarized). 49- The speed of all types of electromagnetic waves is 3.0 x 108 m/sec in a vacuum. 50- The amplitude of a sound wave determines its energy. 51- Constructive interference occurs when two waves are zero (0) degrees out of phase or a whole number of wavelengths (360 degrees.) out of phase. 52- At the critical angle a wave will be refracted to 90 degrees. 53- According to the Doppler effect a wave source moving toward you will generate waves with a shorter wavelength and higher frequency. 54- Double slit diffraction works because of diffraction and interference. 55- Single slit diffraction produces a much wider central maximum than double slit. 56- Diffuse reflection occurs from dull surfaces while regular reflection occurs from mirror type surfaces. 57- As the frequency of a wave increases its energy increases and its wavelength decreases. 58- Transverse wave particles vibrate back and forth perpendicular to the wave direction. 59- Wave behavior is proven by diffraction, interference and the polarization of light. 60- Shorter waves with higher frequencies have shorter periods. 61- Radiowaves are electromagnetic and travel at the speed of light (c). 62- Monochromatic light has one frequency. 63- Coherent light waves are all in phase. |

Geometric Optics 64- Real images are always inverted. 65- Virtual images are always upright. 66- Diverging lens (concave) produce only small virtual images. 67- Light rays bend away from the normal as they gain speed and a longer wavelength by entering a slower (n) medium {frequency remains constant}. 68- The focal length of a converging lens (convex) is shorter with a higher (n) value lens or if blue light replaces red. |

Modern Physics 69- The particle behavior of light is proven by the photoelectric effect. 70- A photon is a particle of light {wave packet}. 71- Large objects have very short wavelengths when moving and thus can not be observed behaving as a wave. (DeBroglie Waves) 72-All electromagnetic waves originate from accelerating charged particles. 73- The frequency of a light wave determines its energy (E = hf). 74- The lowest energy state of a atom is called the ground state. 75- Increasing light frequency increases the kinetic energy of the emitted photo-electrons. 76- As the threshold frequency increase for a photo-cell (photo emissive material) the work function also increases. 77- Increasing light intensity increases the number of emitted photo-electrons but not their KE. |

Internal Energy 78- Internal energy is the sum of temperature (ke) and phase (pe) conditions. 79- Steam and liquid water molecules at 100 degrees have equal kinetic energies. 80- Degrees Kelvin (absolute temp.) Is equal to zero (0) degrees Celsius. 81- Temperature measures the average kinetic energy of the molecules. 82- Phase changes are due to potential energy changes. 83- Internal energy always flows from an object at higher temperature to one of lower temperature. |

Nuclear Physics 84- Alpha particles are the same as helium nuclei and have the symbol . 85- The atomic number is equal to the number of protons (2 for alpha) 86- Deuterium () is an isotope of hydrogen () 87- The number of nucleons is equal to protons + neutrons (4 for alpha) 88- Only charged particles can be accelerated in a particle accelerator such as a cyclotron or Van Der Graaf generator. 89- Natural radiation is alpha (), beta () and gamma (high energy x-rays) 90- A loss of a beta particle results in an increase in atomic number. 91- All nuclei weigh less than their parts. This mass defect is converted into binding energy. (E=mc2) 92- Isotopes have different neutron numbers and atomic masses but the same number of protons (atomic numbers). 93- Geiger counters, photographic plates, cloud and bubble chambers are all used to detect or observe radiation. 94- Rutherford discovered the positive nucleus using his famous gold-foil experiment. 95- Fusion requires that hydrogen be combined to make helium. 96- Fission requires that a neutron causes uranium to be split into middle size atoms and produce extra neutrons. 97- Radioactive half-lives can not be changed by heat or pressure. 98-One AMU of mass is equal to 931 meV of energy (E = mc2). 99- Nuclear forces are strong and short ranged. |

General The most important formulas in the physics regents are: Physics is fun. (Honest!) |

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