Saturday, February 27, 2010

101 Physics facts

    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.


  15. Energy

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


  23. Electricity

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


  38. Magnetism

  39. The direction of a magnetic field is defined by the direction a compass needle points.
  40. Magnetic fields point from the north to the south outside the magnet and south to north inside the magnet.
  41. Magnetic flux is measured in webers.
  42. Left hands are for negative charges and right hands are for positive charges.
  43. 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.
  44. Solenoids are stronger with more current or more wire turns or adding a soft iron core.


  45. Wave Phenomena

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


  68. Geometric Optics

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


  74. Modern Physics

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


  84. Internal Energy

  85. Internal energy is the sum of temperature (ke) and phase (pe) conditions.
  86. Steam and liquid water molecules at 100 degrees have equal kinetic energies.
  87. Degrees Kelvin (absolute temp.) Is equal to zero (0) degrees Celsius.
  88. Temperature measures the average kinetic energy of the molecules.
  89. Phase changes are due to potential energy changes.
  90. Internal energy always flows from an object at higher temperature to one of lower temperature.


  91. Nuclear Physics

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


  108. General

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

Fun Facts !!!

The Roman poet Lucretius (ca. 94–ca. 55 B.C.) wrote a poem in 56 B.C. describing the views of Greek philosophers who, like him, thought the universe to be composed of atoms. This poem is the only record of the beliefs of these early atomists, whose works were lost due to their unpopular views. Lucretius' poem was lost as well, but in 1417, however, a copy was discovered. Its views helped to persuade chemists to consider the atomic theory of matter, a theory that won out eventually.

In 1903, Albert Michelson, one of the 19th century's top physicists, commented "The more important fundamental laws and facts of physical science have all been discovered, and these are so firmly established that the possibility of their ever being supplemented in consequence of new discoveries is exceedingly remote". Two years later, Einstein published his revolutionary Theory of Special Relativity.

The Ancient Greek philosopher Thales noticed that amber decorations on spinning wheels attracted threads, feathers, and other objects through what we now know to be static electricity. The Greek word for amber is elektron, from which William Gilbert, physician to Queen Elizabeth I, coined the word "electricity".

In 1905 Albert Einstein wrote his famous Special Theory of Relativity. It was published in a scientific journal that same year, but took many years to gain general acceptance. In fact, it was not verified by actual experiment until 25 years later. Two years after that paper was published, Einstein wanted a job as assistant professor of mathematics. This job required the applicant to submit a thesis paper, so Einstein submitted his Special Theory of Relativity. The university rejected it.

The quark, a building block of the proton, got its name from James Joyce's Finnegans Wake, from the line "Three quarks for Muster Mark! Sure he hasn't got much of a bark". [

According to the laws of gravity, the moon technically does not orbit the Earth. The two bodies actually both orbit around their common centre of gravity, which is located 1,000 miles beneath the surface of the Earth and is on a straight line between the centres of the Earth and moon. The centre of the Earth makes a small circle around that centre of gravity every 27 1/3 days. [

According to the rules of logic, the question "What would happen if an irresistible force met an immovable object?" is meaningless. In a universe where one of the above conditions exists, by definition the other cannot exist.

A "light year" is a measure of distance, not time. It is defined as the distance light travels in one year. Light moves at a velocity of about 300,000 kilometres each second, so in one year, it travels about 9,500,000,000,000 kilometres. [

To the nearest ten-thousandth of a mile, light travels at 186,282.3959 miles per second. At that rate, it takes slightly more than eight minutes to get to Earth from the sun. However, it takes light hundreds of years to travel from the sun's centre to its surface. The light must take a very indirect path to the surface due to the large number of collisions with particles within the sun.

In 1940, the Tacoma Narrows Bridge (popularly known as "Galloping Gertie"), which spanned the Puget Sound south of Seattle, opened. At the time it was the third longest bridge in the world and narrower than any comparably-sized bridges. Although the bridge was criticized for being too slender, Leon Moisseiff, the consulting engineer to the project and an expert on suspension bridges, assured people that the bridge would be safe. However, only three months after it opened, the bridge collapsed in a 42 mph wind after going into harmonic oscillation.

An atomic clock kept at the National Bureau of Standards in Boulder, Colorado, U.S.A., 1650 metres above sea level, gains about five microseconds each year relative to an identical clock kept at the Royal Greenwich Observatory, 25 metres above sea level. The reason is that gravity gets stronger as one gets closer to the Earth's core, and, according to Einstein's Theory of Relativity, time is slower in stronger gravitational fields.

A perpetual motion machine would violate the laws of thermodynamics. No-one has ever built one, and no-one ever will.

According to the Second Law of Thermodynamics, the amount of entropy in the universe always increases, which means that eventually, the universe must run down and life in the universe will cease.

Information about what has fallen into a black hole is stored on the event horizon of a black hole. Recent calculations by the folks who study quantum gravity theory and superstrings have confirmed what Stephen Hawking and his collaborators proposed a decade or more ago. Evidently, the information contained in matter that falls into a black hole is by some curious means encoded in the pattern of frozen quantum fields at the horizon. This raises some interesting possibilities that we could resurrect clocks, humans, spacecraft, and whole planets into something like their pristine form if we could magically reverse the in-fall and collapse process. Many believe that this mathematical result means that we have reached a watershed moment in history in understanding the connection between quantum mechanics and gravitation theory. Quantum mechanics deals with statements about the information that we can extract about a quantum mechanical process involving observation. Now this same information language can be applied to configurations of the gravitational field and space-time itself. [

Light has weight. The weight of sunlight on the earth's surface has been determined to be two pounds per square mile.

The sky is blue because of refraction. The sun's light is of all colours of the rainbow, mixed together to make white light. The reds and yellows pass through air easily, but some of the blue portion of sunlight is scattered in every direction by air molecules. This scattering causes the sky to be blue.

An article in the April 26, 1993 article of Physical Review Letters, titled "First Measurement of the Left-Right Cross-Section Asymmetry in the Boson Production by e+ e- Collisions", had 407 authors.

Can you hear in space? In theory, if there is nothing to receive the sound, there is no sound. Because there are no "air waves" in space to conduct the sound, it would not carry. So, the object would make a noise, but it would not carry to any receiver, and no one would hear it. [

There is sound in space. What is sound? It is a pressure wave. So long as you have some kind of gaseous medium, you will have the possibility of forming pressure waves in it by "shocking" it in some way. In space, the interplanetary medium is a very dilute gas at a density of about 10 atoms per cubic centimeter, and the speed of sound in this medium is about 300 kilometers per second. Typical disturbances due to solar storms and "magneto-sonic turbulence" at the Earth's magnetopause have scales of hundreds of kilometers, so the acoustic wavelengths are enormous. Human ears would never hear them, but we can technologically detect these pressure changes and play them back for our ears to hear by electronically compressing them. [

Since the 1950s, physicists have discovered over 200 different kinds of particles.

The difference between the appearance of a real object and its reflection in a mirror is that the clockwise and counterclockwise directions are switched.

Newton's Third Law of Motion states that for every action there is an equal and opposite reaction.

When an airplane travels at a speed faster than sound, density waves of sound emitted by the plane accumulate in a cone behind the plane. When this shock wave passes, a listener hears a sonic boom.

It is not known exactly what gravity is. We can define what it is as a field of influence, and with general relativity we can define a language which states that it is a property of our real world that is mathematically equivalent to not just the geometry of space-time, but equivalent to space-time itself. Some think that it is made up of particles called gravitons, which flit about at the speed of light just as photons do. In any true fundamental sense, we do not know what gravity is, we only know how it operates in various corners of our universe. Without gravity, there would be no space and time.

Around one percent of the static on a television set tuned between stations is a relic of the Big Bang.

Ordinary matter consists almost entirely (99.9999999999999%) of empty space.

Bell's Theorem states that certain measurements made on one particle can instantaneously affect the measurements made on a second particle that, in theory, could have been removed to the opposite side of the galaxy, with no physical connection between the two.

The size of Earth is roughly the geometric mean of the size of the universe and the size of an atom, and the mass of a human is roughly the geometric mean of the mass of Earth and the mass of the proton.

Interesting Facts of Physics

E=mc2


1.The effect of Relativity made Astronaut Sergei Avdeyev a fraction of a second younger upon his return to Earth after 747 days in space. Submitted by: Moi - Canada

Dead Sea

2.The Dead Sea is so dense with salt, you can easily float on it without drowning.

Lake Baikal

3.Lake Baikal in Russia contains more water than all the North American Great Lakes combined.

black ironwood tree

4.The world's densest wood, the Black Ironwood (Olea laurifolia), does not float on water and therefore sinks.

5.The mass of our entire atmosphere is estimated to be some 5.5 quadrillion tons (55 followed by 14 zeros).

6.Chewing gum was invented by a dentist, named William Semple - as a way to exercise your jaws.

7.The diameter of a proton is approximately 0.000000000001 mm (1/25,000,000,000,000 inch).

diamond

8.You can convert graphite into diamond by applying a temperature of 3000 Celsius and pressure of 100,000 atm.

9.The amount of water beneath our ground soil is 50 times as much as all the water in the rivers and lakes combined.

10.The first ten feet of the ocean hold as much heat as the Earth's entire atmosphere.

lightning bolt

11.The lightning bolt is 3 times hotter than the sun. Submitted by: Jieian

12.On average, our bodies constantly resist an atmospheric pressure of about 1 kilogram per square inch.

mariana trench

13.The deepest location on Earth is Mariana Trench, about 11km deep in the North Pacific ocean.

Redwood tree

14.The bark of the redwood tree is fireproof.

Everest in ocean at Mariana Trench

15.If Mount Everest were placed at the bottom of the deepest part of the ocean, its peak would still be a mile underwater. Submitted by: Nikhil, India

16.If given the same mass, our body would actually be hotter than the sun. Submitted by: Eddy - United States

wormhole

17.Many physicists believe wormholes (a "shortcut" through space and time) exist all around us but they are smaller than atoms. Submitted by: Jay - United States

mojave desert

18.A solar panel 100 miles by 100 miles (161x161km) in the Mojave Desert (USA) could replace all the coal now burned to generate electricity in the entire U.S.

19.The Atlantic Ocean grows at about the same rate as your fingernails.

20..If you yelled for 8 years, 7 months and 6 days, you would have produced just enough sound energy to heat up one cup of coffee.

21.The average ice berg weighs 20,000,000 tons.

lightning

22.Lightning strikes about 6,000 times per minute on our planet.

23.A gallon of water weighs 8.34 pounds (3.8kg).

24.If an item moves very, very fast, it becomes smaller and heavier.

25.Minus 40 degrees Celsius is exactly the same temperature as minus 40 degrees Fahrenheit.

26.Hot water freezes quicker than cold water.

Pumice floating

27.The only rock that floats in water is pumice.

28.Mexico City is sinking at a rate of 18 inches (46cm) per year as a result of draining water.

29.1 inch (25mm) of rain water is equivalent to 15 inches (381mm) of dry, powdery snow.

largest meteorite crater

30.The oldest and largest clearly visible meteorite crater site in the world is The Vredefort Dome in Free State, South Africa. It is 380km across.

31.The greatest tide change on earth occurs in the Bay of Fundy. The difference between low tide and high tide can be as great as 16.6 meters (54 ft.)

32.The temperature in fahrenheit can be determined by counting the number of cricket chirps in 14 seconds and adding 40.

33.The average ocean floor is about 3,600 meters deep (12000ft).

34.Sunlight can penetrate clean ocean water to a depth of 73 meters (240ft.)

35.The North Atlantic gets 2.5 centimetres (1in) wider every year.

36.Hawaii is moving toward Japan 10 centimetres (4 inches) every year.

37.Due to gravitational effects, you weigh slightly less when the moon is directly overhead.

Lake Baikal

38.Lake Baikal is the deepest lake in the world.

39.When hydrogen burns in the air, water is formed.

diamond
40.Diamonds are the hardest known substance.