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KHS Physics Spring Final Review Spring 2012 1. KE is energy of motion. PE is energy of position 2. KE = ½ m v2 and PE = mgh 3. Thermal Energy- is the sum of the kinetic and potential energy of all the molecules in an object. 4. Heat transfer problems Q = m c T Where m = mass (kg) c = specific heat of the material T = Tf - Ti (change of temperature in C Change of Phase problems Q = mHf Q =mHv Where m = mass (Kg) Hf = heat of fusion Where m = mass (Kg) Hv = heat of vaporization 5. The total potential and kinetic energy of all microscopic particles in an object make up it's thermal energy. 6. Joules 7. a. Solid phase a b. Liquid phase c c. gas Phase e d. Melting b e. Boiling d 8. Hot to cold 9. Three methods of heat transfer: a. Conduction- The transfer of thermal energy through matter by the direct contact of particles. Examples: Touching a stove and being burned -Ice cooling down your hand -Boiling water by thrusting a red-hot piece of iron into 1 b. Convection- the transfer of energy in a fluid by the movement of the heated particles. Examples: Hot air rising, cooling, and falling (convection currents) -An old-fashioned radiator (creates a convection cell in a room by emitting warm air at the top and drawing in cool air at the bottom). c. Radiation- The transfer of energy by electromagnetic waves. Examples: Heat from the sun warming your face -Heat from a lightbulb -Heat from a fire 10. a. Thermal conductor- A material that conducts heat well and quickly Examples: metals b. Thermal Insulator- A material that does not conduct heat well Examples: wood, brick plastics 11. Specific heat - the amount of energy that must be added to raise the temperature of one kilogram of the material one degree Celcius Q = m c T Where m = mass (kg) c = specific heat of the material T = Tf - Ti (change of temperature in C Units of c is J/kgC° 12. Temperature -measure of an object’s kinetic energy; temperature measures how hot or how cold an object is with respect to a standard units C°, K and F° 13. Laws of Thermodynamics First Law OF THERMODYNAMICS – HEAT ADDED TO A SYSTEM = INCREASE IN INTERNAL ENERGY + EXTERNAL WORK DONE BY THE SYSTEM: Q = U + W 2 SECOND LAW OF THERMODYNAMICS- NATURAL PROCESSES GO IN A DIRECTION THAT MAINTAINS OR INCREASES THE TOTAL ENTROPY OF THE UNIVERSE. 14. Density Density is a physical property of matter that is defined as the ratio of an object's mass to its volume. We can calculate density using the formula: Density= Mass/Volume Wave Properties and Behaivor Matching 15. Period g 16. Reflection h 17. Refraction i 18. Wave k 19. Amplitude a 20. diffraction c 21. Interference f 22. frequency d 23. hertz e 24. wavelength l 25. wave motion m 26. crest b 27. trough j 28. Reflection – the bouncing back of a wave. Uses: Radar, echo, mirrors 29. Refraction Refraction of waves involves a change in the direction of waves as they pass from one medium to another. Refraction, or bending of the path of the waves, is accompanied by a change in speed and wavelength of the waves. Uses: eye glasses, cameras and fiber optics 30. Identify parts of a wave 3 Parts of a wave Crest Trough Wavelength Compression Rarefaction 31. Longitudinal Wave Transverse Wave Transverse wave- Particles move perpendicular to the direction of the motion of the wave. Longitudinal wave- Particles move parallel to the direction of the wave. 4 32. Electromagnet Spectrum All electromagnetic waves travel at the speed of light in a vacuum. A. A standing wave – also known as a stationary wave – is a wave that remains in a constant position. 5 33. Wave type Electromagnetic Mechanical speed Speed of light Medium Can travel in vacuum Need medium Much slower depends on medium Example Light Water wave 34. Frequency of a wave is inversely proportional to the wavelength. 35. Wave speed is independent of amplitude. 36. Given: T = 4 s and λ = 3 m a. f = 1/T, thus f = ¼= .25 hz b. v= fλ thus, v= 3x .25 = .75 m/s 37. f = 500 hz, λ = .1 m v = f x λ v= 500 x .1 = 50 m/s v = d/t t = d/v t = 2000m/ 50 m/s = 40 s 38. Sound- Sound is energy that is produced by the compression and rarefaction of matter. It travels as a longitudinal wave. 39. define a. Pitch- the frequency of the wave. b. Loudness-The amplitude of sound c. Resonance- to vibrate at the same frequency, which increases the amplitude of the wave. d. Doppler Effect- change in frequency due to relative motion of source and detector. 6 40. You hear the high pitch of the siren of the approaching ambulance, and notice that its pitch drops suddenly as the ambulance passes you. That is called the Doppler effect. 41. Volume is directly proportional to the amplitude of the wave. 42. See above 43. Light is a transverse wave that travels at 3 x 108 m/s in a vacuum. 44. The differences between light and sound are as follows: Light can be considered to be made of waves as well as particles. Sound is only a wave. It does not show particle nature. Light waves are electromagnetic waves while sound waves are mechanical waves. Light waves are transverse while sound waves are longitudinal. Light waves can travel in vacuum. Sound waves require a material medium to travel, and hence, cannot travel in vacuum. The speed of light in a medium is constant. The velocity of sound waves can change. In sound waves, the particles of the medium actually oscillate. In a light wave, the electric and magnetic vectors oscillate. Light waves can be polarized, but sound waves cannot. Light waves travel much faster than sound waves. The speed of light is a physical constant. Its value is exactly 299,792,458 metres per second in vacuuum. The speed of sound is 343 metres per second in dry air at 20°C. 7 And finally, a simple one - you can see light while you can hear sound. From http://wiki.answers.com/Q/What_is_the_difference_between_light_waves_and_sound _waves 45. 34. Electromagnet Spectrum 8 46. v= λ x f Light with a lower frequency will have a longer wavelength. Frequency and wavelength are inversely proportional to each other (i.e. as one increases, the other decreases and vice-a-versa). The product of frequency and wavelength is the speed of light. 47. Snell’s law: light traveling from medium to medium ni sinӨi = nr sinӨr 1 sin49 = 1.76 sin θ θ= sin-1 (sin49/1.76) = 25.39° 48. Total internal reflection- Occurs when light passes from a more optically dense medium to a less optically dense medium at an angle so great that there is no refracted ray. 49. Electric charge is a physical property of matter which causes it to experience a force when near other electrically charged matter. Electric charge comes in two types, called positive and negative. Unit of charge- 1 Coulomb 1 Coulomb = charge of 6.25 x 1018 electrons 9 50. Charges are not created but separated. (i.e. electrons can be removed from or added to atoms) An increase or decrease in the number of electrons in an object gives it an electrical charge. When an object gains electrons, it becomes negatively charged. When it loses electrons, it becomes positively charged. 51. Two positively charged substances, or objects, experience a mutual repulsive force, as do two negatively charged objects. Positively charged objects and negatively charged objects experience an attractive force. 52. Coulomb’s Law- The magnitude of the force that a tiny sphere with charge q exerts on a second sphere with charge q’, separated by a distance d. F = k q q’/ d2 where k = 9 x 109 Nm2/C2 q,q’- charges in Coulombs d – distance in meters F – Newtons 53. Variables that affect electrical force Charge- directly proportional Distance- inverse square law 54 Electric field – Property of space around a charged object that causes forces on other charged objects. An electric field is a vector with both magnitude and direction. The direction of the electric field is the direction of the force on the positive test charge. Electric field lines- lines representing the direction of the electric field. Note: the spacing between the lines indicates the strength of the electric field. The field is strong where the field lines are closed together 10 55. A series circuit is a circuit in which resistors are arranged in a chain, so the current has only one path to take. The current is the same through each resistor. The total resistance of the circuit is found by simply adding up the resistance values of the individual resistors: equivalent resistance of resistors in series : R = R1 + R2 + R3 + ... 56. A parallel circuit is a circuit in which the resistors are arranged with their heads connected together, and their tails connected together. The current in a parallel circuit breaks up, with some flowing along each parallel branch and re-combining when the branches meet again. The voltage across each resistor in parallel is the same. The total resistance of a set of resistors in parallel is found by adding up the reciprocals of the resistance values, and then taking the reciprocal of the total: equivalent resistance of resistors in parallel: 1 / R = 1 / R1 + 1 / R2 + 1 / R3 +... 11 57. The total resistance of the circuit is found by simply adding up the resistance values of the individual resistors: equivalent resistance of resistors in series : R = R1 + R2 + R3 + ... The total resistance of a set of resistors in parallel is found by adding up the reciprocals of the resistance values, and then taking the reciprocal of the total: equivalent resistance of resistors in parallel: 1 / R = 1 / R1 + 1 / R2 + 1 / R3 +... 58. Need values of resistors. Would use I = V/R 59. Use P = VI P = 12x5 = 60 watts 60. V = IR V = 5x 2.4 = 12V 61. P = VI If power is held constant, then Voltage and current are inversely proportional. 62. All magnets are caused by the movement of electrons. No moving electrons = no magnet. In a permanent magnet, several adjacent electrons have the same spin - they form a magnetic domain. 63. A permanent magnet retains its magnetic properties for a long time. Temporary magnets are those that simply act like permanent magnets when they are within a strong magnetic field. 12 64. Magnetic fields 1. Magnetic field- Space around a magnet throughout which magnetic force exists. 2. Iron filings around a magnet can represent magnetic field lines. 3. The greater the number of field lines, the stronger the magnetic field 4. The direction of the magnetic field lines is defined as the direction to which North pole of a compass points when it is placed in the magnetic field. 5. The field lines come out of the magnet at its North pole and enters the magnet at its South pole. 6. The magnetic lines are most concentrated at the poles where the magnetic field is the greatest. 65. The magnetic lines are most concentrated at the poles where the magnetic field is the greatest. 66. An electromagnet is a type of magnet whose magnetic field is produced by the flow of electric current. The magnetic field disappears when the current ceases. 67. Increase the number of turns or increase the current. 13 68. The photoelectric effect refers to the emission, or ejection, of electrons from the surface of, generally, a metal in response to incident light. Analysis of data from the photoelectric experiment showed that the energy of the ejected electrons was proportional to the frequency of the illuminating light. This showed that whatever was knocking the electrons out had an energy proportional to light frequency. The remarkable fact that the ejection energy was independent of the total energy of illumination showed that the interaction must be like that of a particle which gave all of its energy to the electron! 69. The wave particle duality principle of quantum physics holds that matter and light exhibit the behaviors of both waves and particles, depending upon the circumstances of the experiment. 70. Phenomenon Can be explained in terms of waves. Can be explained in terms of particles. Reflection Refraction Interference Diffraction Polarization Photoelectric effect 71. E = Hf As frequency of light increases, the energy of light increases. 14 72. E= mc2 Einstein 73. The equation E = mc2 indicates that energy always exhibits mass in whatever form the energy takes.[3] Mass–energy equivalence also means that mass conservation becomes a restatement, or requirement, of the law of energy conservation, which is the first law of thermodynamics 74. As a part of the medical subspecialty of Nuclear Medicine, various diagnostic procedures make use of a small amount of a radioactive isotope, usually injected into the patients bloodstream for the purpose of imaging some part of the body. The useful radiation from such isotopes is usually gamma rays, which can be detected outside the body. These gamma rays can be used to image an internal organs or structures. 75. Nuclear plant uses control rods to absorb excess neutrons that are released in a fission reaction. 76. Nuclear stability means that nucleus is stable meaning that it does not spontaneously emit any kind of radioactivity. 15