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Bearing in mind article 70, physical score to come up

Many students in the study of physics tend to drop points at some point in the process, therefore, we summarize some of the common error-prone points summed up, I hope the students can remember a careful analysis, so as to improve physical efficiency.

1. straight line speed must be constant. As long as the body, the speed must be a fixed value.

2, density is not necessarily the same. Density is the physical attributes, and unrelated to mass-volume, and temperature, especially gas density follow temperature changes more clearly.

3, the average speed is only the total distance divided by the total time. Seeking a period of average speed on the road, not an average speed, can only be spent on the total distance divided by the distance of all time, including intermediate stops time.

4, scale readings, tour code depends on the left side, mobile tour code is equal to plus or minus weight in the balance right.

 5 and force analysis of the steps: determining the object of study; looking for gravity; touching; judgment and contact objects between the pressure, force, friction, tension, and other forces.

6, physical activity status change must be force, force not change state. Force to change the motion State of reason. Stress also contains the balance, movement status is unchanged.

7, inertia and speed. Inertia with regard to quality. Velocity only shows the more kinetic energy and be able to do more, not greater inertia.

8, the balance and interaction of differences: the force acts on a body, forces acting on the two objects.

9. is the property of inertia is not. Cannot be said to be only due to.

10. objects, balance object at equilibrium (rest or of uniform motion). Both of these can be derived. Objects in non-equilibrium: force and motion in the same direction, accelerating movement of objects, on the contrary, the deceleration.

11.1Kg≠9.8N。 Two different physical quantities can only use formulas to transform.

12. weight beam, balance on the moon can use, weightlessness in space the balance and spring dynamometer can also measure tensile force cannot be used in addition to forces other than gravity.

13. the pressure increase friction does not necessarily increase. Sliding friction is related to pressure, but pressure has nothing to do with static friction, just and balanced force.

14. two objects does not necessarily occur in the role. To see squeeze, relative motion, and so on.

15. the friction and contact surface roughness related to pressure and the size of the contact area.

16. leverage leveling: Zuo Gaozuo tune; balance leveling: pointers about tone. Nut, adjust the direction of balance on both sides.

17. pulley half of a certain province. Only in a vertical or horizontal direction, to half power.

18. the method of drawing arm: a pivot (a stationary point on the lever), draw a line of action of force (extended or reverse the extension force), three distances (Fulcrum, the vertical line of action of force), four subscripts.

19. power minimum lever should be Max. Arm of the biggest practices: is found on the lever, making this the farthest distance from the fulcrum.

20. pressure bearing area of contact area, M2. Note the contact area are one or more than one, also to pay attention to unit conversion: 1cm2=10-4m2

21. the liquid pressure has nothing to do with the weight and shape of liquid column, only concerned with the depth of liquid. Depth refers to the liquid level of liquid within a point of distance, not height.

solid pressure calculated with the F=G pressure, calculated with the P=F/S pressure, the liquid pressure to use p = ρ GH calculation pressure, calculated with the F=PS pressure (note the units, cylinders, two methods can be used)

22. the Torricelli experiment mercury column height differences and factors such as the thickness of the pipe inclined not only concerned with the prevailing atmospheric pressure.

23. buoyancy and depth not only related to the object submerged in a fluid volume. Immerse v row of =V, there is no immersion v row

find buoyancy would be the first to look at the State of the object: floating or suspended if they are simply calculated according to the float f = g, if weight beam measurement can be calculated according to the floating =G-F f, if density and volume are calculated according to the float f = ρ GV.

24. powerful does not necessarily work. Strong distance and distance work.

25. the mechanical efficiency of simple machines are not set in stone. Mechanical efficiency of the pulley with besides gravity with pulley of lifting objects by gravity, the heavier object, pull more, higher mechanical efficiency, but blocks the gravity constant.

26. uniform horizontal movement of objects, kinetic energy and potential energy is not necessarily the same. Also taking into account the mass of the object is changed, such as sprinklers, cast plane of relief supplies.

27. when the conservation of mechanical energy, kinetic energy is maximum and minimum potential energy. From easy analysis of deformation height and size to determine potential energy, then judge the change in kinetic energy.

28. the attraction and repulsion between molecules are there, and increases and decreases. Just in a different process, changing speed of attraction and repulsion are not the same, leading to the final size of the attraction and repulsion are not the same, and ultimately the performance of attraction or repulsion.

29. gravity and atmospheric pressure differences between molecules: molecular forces are due to Intermolecular attraction of mutual attraction, but if the air is discharged or changes the description of the atmospheric pressure is the atmospheric pressure. Example: two pieces of glass together, not separate after water is atmospheric pressure, lift the glass surface spring dynamometer readings become smaller because of attraction between molecules.

30. objects within increases, temperature does not necessarily increased (Crystal melting, liquefied boiling); objects within increased, does not necessarily is hot passed (also can is work); objects endothermic, within must increased; objects endothermic temperature does not necessarily increased (Crystal melting, liquid boiling); objects temperature increased, within does not necessarily increased (also and objects of quality, factors about); objects temperature increased, does not necessarily is hot passed (also can is work).

31. the internal energy and temperature, mechanical energy and objects relating to mechanical motion, they are two different forms of energy. Objects must be within, but not necessarily mechanical energy.

32. the heat exists only in the heat transfer process, leaving the heat transfer that heat is of no significance. Heat corresponding verbs are: absorption or release.

33. specific heat is a property of the material, is set in stone. Specific heat capacity: absorb the same heat, small temperature variation (artificial lake climate comfort); increased temperature, absorbing more heat (water as coolant).

34. a work cycle consists of four-stroke internal combustion engine, the crankshaft turns two weeks, work time, two energy conversion.

35, nuclear energy belongs to the primary energy, fossil energy.

36, solar is the solar energy into electrical energy. Not convert chemical energy into electrical energy.

37. the current use is mainly controlled nuclear fusion (nuclear reactors). Inside the Sun constantly undergoing nuclear fusion.

38. the high and low tones of the voice, and the frequency, and a voice related to body length, thickness, elastic.

size of the loudness of the voice, and related to the amplitude, and the size of the force and proximity to sound relevant.

is used for distinguishing different vocal timbre, and vocal material and structure. (Life's circumstances with high and low to describe the loudness of sound)

39. echo-ranging attention should be divided by 2

40. the note plus the arrow of light, to pay attention to the difference between solid and dotted lines: real image, the light was solid; extension of the normal, illusion, Ray was dashed.

41. the reflections and split shot is always at the same time,

42. the diffuse and specular reflections are in compliance with the law of reflection of light.

43. the plane mirror formation of image: illusion, to draw a dashed line, second largest, people out of the mirror, remain the same size, but angle smaller, feels like a small, real constant.

44. camera distance: the distance between object and camera, image distance: the film to mirror clearance distance or length of the Camera Obscura. The distance of the projector: film to lens distance, distance: the distance between screen and projector.

45. the principle of the camera: u>2F, upside down, narrowing the real image, projector works: 2f>u>f, into a inverted, magnified real image.

46. the transparent colors by shade and decides, and objects of the same color of light through, different coloured light is absorbed.

47. liquefaction: fog, dew, rain, white gas. Sublimation: snow, Frost, rime. Solidification: hail, icicles in the roof.

48. vaporized in two ways: evaporation (any temperature) and boiling (temperature). Liquefaction of two methods: reduce the temperature and compression volumes.

49. the boiling bubbles go up higher, before boiling bubbles up smaller.

50. the Crystal melting point common are: sea ice, quartz, Crystal and metal amorphous no melting point, common: wax, Rosin, pitch, glass.

51. the six changes of State:

52. the conditions of melting and boiling of liquid crystal: reaches a certain temperature (melting and boiling points) II continue to heat.

53. the conductive metal by free electrons, free electrons moving direction and the current in the opposite direction.

54. in series and parallel electric only, does not include a switch, and meter. Only one series circuit current paths, without the diversion point, parallel circuit current paths, the diversion point.

55. the judge whose voltage voltmeter test method available: first remove the power supply and voltage meter, voltmeter as power analysis, from one end to the other, see circle measuring anyone's voltage.

56. even circuit Shi, beginning to disconnect; sliding tablets put in resistance maximum of location; ammeter General with small drive; voltage table of range to see power voltage and by measuring with electrical of rated voltage; sliding rheostat to a Shang about, and to see topics given of conditions first Optional even left Xia or right Xia; voltage table must to put in last again and in by measuring with electrical of ends.

57. it must have a voltage of electric current in the circuit, but the voltage is not necessarily a current (circuit closed).

58. the properties of the resistance of a conductor is generally unchanged (particularly resistance), but temperature, higher temperature resistance the greater the filament resistance most obvious.

59. a series circuit is a flow divider, is proportional to the voltage and resistance, that is, greater resistance, voltage is.

a parallel circuit is shunt, current and inversely proportional to the resistance, that is, greater resistance, less current.

60. the measuring wire resistance and the circuit diagram of the power, experimental equipment, too, but the principle is not the same. (R=U/I and P=UI, respectively), requiring multiple measurement average measuring resistance, reducing errors, but power measuring power is changing, so average does not make sense.

61. the power meter is the difference between the two readings, the last one is a decimal number.

62. the computing power can be calculated by the h and KW, then use 1KWh=3.6x106J conversion.

63. the rated power and rated voltage is not constant, but the actual voltage and power is changing. But when resistance is constant. Resistance can be calculated according to R=U2/P.

64. the switch must be in the circuit and the lights of the family series, the switch must be in the line of fire, light spirals on the zero line fuse in the line of fire after another can, Jack is left 0 right on the fire ground.

65. the s Pole on a magnet Guide (geographical South level, magnetic north, ordinary is the geographical poles) n pole refers to the North.

66. Oster discovered the magnetic effects of electric current (ohmic conductor surrounded by a magnetic field) to make motor, Faraday discovered Electromagnetic induction, generators have been made. Shen discovered the magnetic declination. Thompson discovered the electron. Lu Safu-nuclei structure model is established, Bell invented the telephone.

67. the disk, a hard disk, the application of the magnetic material, disc magnetic material is not applied.

68. the speed of an electromagnetic wave is equal to the speed of light is inversely proportional to the wavelength and frequency.

69. the principle of motor: force turn coil in a magnetic field, the electric energy into mechanical energy. Outside the circuit has power.

 70. generator principle: electromagnetic induction, the mechanical energy into electrical energy, external circuit have no power.

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