The outline of physics midterm review

The outline of physics midterm review

1) Acoustic phenomenon
Physics is the study of sound, light, heat, electricity, force and other physical phenomena
2. Sound is produced by the vibration of objects. The transmission of sound needs medium. Vacuum cannot transmit sound
3. Three characteristics of sound:
① Tone: it is determined by the frequency of vibration. The faster the frequency, the higher the tone
② Loudness: determined by the amplitude of the object vibration, the greater the amplitude, the greater the loudness
③ Timbre: determined by the material and structure of the object, the timbre of different objects is different
4. The basic process of people hearing sound:
① Vibration of tympanic membrane → auditory ossicles and other tissues → auditory nerve → brain
② Jaw, skull, auditory nerve, brain
5. The function of sound: transmitting information and energy
6. All the sounds that affect people's normal study and life are noise. In order to protect hearing, the sound should not exceed 90dB; in order to ensure work and study, the sound should not exceed 70dB; in order to ensure rest and sleep, the sound should not exceed 50dB
(2) Change of state of matter
1. Temperature: the degree of coldness and hotness of an object is called temperature. Unit: centigrade (℃): the temperature of ice water mixture -- 0 ℃; the temperature of boiling water -- 100 ℃
2. The principle of thermometer: it is made of the nature of liquid expansion and contraction. The commonly used liquids are Mercury, alcohol, kerosene, etc;
Third reading:
(1) wait until the thermometer is stable before reading;
The glass bubble cannot leave the liquid level when reading;
When reading, the eye should be level with the upper surface of the liquid column of the thermometer
4. Thermometer: range: 35 ℃ ~ 42 ℃; graduation value: 0.1 ℃; throw mercury down before use
5. Change of state the process of a substance from a solid state to a liquid state is called melting; melting is endothermic. The process of a substance from a liquid state to a solid state is called solidification; solidification is exothermic. The process of a substance from a liquid state to a gas state is called vaporization; vaporization is endothermic. The process of a substance from a gas state to a liquid state is called liquefaction; liquefaction is exothermic. The process of a substance from a solid state to a gas state is called sublimation; sublimation is endothermic The process of changing a state into a solid state is called condensation, which releases heat
6. The common crystals are ice, sea waves and various metals; the non crystals are wax, asphalt, rosin, glass, etc. it is required to distinguish the melting and solidification images of crystal and non crystal
7. The crystal should absorb heat in the process of melting, but the temperature remains the same; the crystal should release heat in the process of solidification, but the temperature remains the same; the melting point and freezing point of the same crystal are the same. The amorphous should absorb heat in the process of melting, and the temperature keeps rising; the amorphous should release heat in the process of solidification, and the temperature keeps falling
There are two ways of vaporization: boiling and evaporation
1 boiling:
a. Definition: at a certain temperature, at the same time in the liquid surface and internal violent vaporization
b. Boiling conditions: ① reach boiling point; ② continue heating
c. Characteristics of boiling: the liquid should absorb heat when boiling, but the temperature remains unchanged
2 evaporation:
a. Definition: at any temperature, only occurs in the liquid surface gasification phenomenon
b. Factors affecting the speed of evaporation: the speed of air flow on the liquid surface: the faster the air flow, the faster the evaporation; liquid temperature: the higher the temperature, the faster the evaporation; liquid surface area: the larger the surface area, the faster the evaporation
c. Evaporation has a cooling effect
8. There are two ways of liquefaction: reducing temperature and compressing volume
9. It can explain all kinds of phenomena of state change in daily life, such as the formation of fog, dew, frost, hail, snow, all kinds of "white gas", the ice flower beside the window, the smaller the sanitary ball, the blackening of the lamp tube, the thinner the filament, the ice into water, the molten iron into steel parts, etc
10. The boiling point of water is related to atmospheric pressure: the higher the atmospheric pressure, the higher the boiling point
(3) Light phenomenon
1. The propagation velocity of light in vacuum: C = 3 × 10 8 m / s
2. Sound propagation speed in air: v = 340 m / S
3. Elementary charge: e = 1.6 × 10 – 19 C
1. Light propagates along a straight line in the same homogeneous medium. (for example, laser guided tunneling, the formation of solar eclipse, lunar eclipse, shadow formation, the "three points and one line" used in aiming and small hole imaging are all obtained by using the principle of light straight line propagation.)
2. Light source:
Natural light source: such as jellyfish, sun, firefly, etc
Artificial light source: such as electric lamp, flashlight, candle, etc
Three primary colors of light: red, green and blue
4. Light will reflect on the surface of any object
5. The law of light reflection
① Incident light, normal and reflected light are in the same plane (three lines in the same plane)
② Incident light and reflected light are separated on both sides of the normal
③ Reflection angle I = incidence angle R
The refraction law of light is as follows
① When light enters other media from air, the refracted light deflects toward the normal
② When light enters the air from other media, the refracted light is far away from the normal
① The size of an image is equal to that of an object
② The distance between the image and the plane mirror is equal to the distance between the object and the plane mirror
③ The line between the image and the object is perpendicular to the plane mirror
④ The image formed by a plane mirror is a virtual image
6. In the phenomenon of light reflection and refraction, the light path is reversible
7. There are two kinds of reflection: specular reflection and diffuse reflection
8. Function of infrared ray and function of ultraviolet ray
① Infrared remote control
① Bactericidal action
② Infrared night vision system
② To make a fluorescent substance glow to judge whether it is true or false
③ Detection of the patient's health
③ Promote the synthesis of vitamin D, help the absorption of calcium
9. Spectral sunlight decomposes into red, orange, yellow, green, blue, indigo and purple
(4) Lens and its application
1. Convex lens: thick in the middle and thin at the edge
2. Concave lens: thin in the middle and thick at the edge
3. Convex lens converges light and concave lens diverges light
4. Be able to find out the main optical axis, focus and focal length
5. Object distance (U) → distance between object and convex lens. Image distance (V) → distance between image and convex lens. Convex lens imaging law: relationship between object distance and focal length, relationship between image distance and focal length, virtual and real of positive and negative images, large and small images, u > 2F

Eighth grade volume 1 physics Chapter 4 Section 1 review outline

1、 Temperature: temperature: temperature is a physical quantity used to indicate the degree of heat and cold of an object. Note: for a hot object, we say its temperature is high, while for a cold object, we say its temperature is low. If two objects have the same degree of heat and cold, their temperatures are the same. It is generally unreliable for us to judge the degree of heat and cold of an object by feeling

Experimental inquiry questions (Physics of Beijing Normal University Edition, Grade 8)
One year, when Hebei Province adjusted some county boundaries, Qingyuan County drew a piece of land for neighboring counties. At this time, the leaders of Qingyuan County need to know what the area is after the adjustment of county boundaries. According to the county map, there are twists and turns around the county boundaries, neither rectangular nor round, Its area obviously can't be calculated by general mathematical formula. Can you come up with a set of calculation scheme? (hint: try to divide the map into several squares)
I hope you can help me with the winter homework of physics in Beijing Normal University. Thank you
Please answer carefully

Draw a lot of horizontal and vertical lines with equal spacing on the map, and draw more appropriately. In this way, you can get many identical small squares. Set the side length of each small square as a, and count the number of small squares (at the boundary, if it is larger than half grid, it will be counted as one grid, but if it is smaller than half grid, it will not be counted, because the chances of larger than half grid and smaller than half grid are equal), Then the area is n * a * a

Cuboid water tank, the bottom is square, water tank height 5 decimeters, its side area is 50 square decimeters, this water tank can hold water how many kilograms?
One cubic decimeter of water weighs one kilogram

Side area = water tank height × bottom edge length
Bottom edge length = side area △ water tank height = 50 △ 5 = 10 decimeters
Bottom area = bottom edge length × bottom edge length = 10 × 10 = 100 square decimeters
Volume = bottom area × tank height = 100 × 5 = 500 cubic decimeter
Water capacity = 500 kg

As shown in the figure, AB and CD are the two chords of circle O, and AB / / CD, Mn bisects AB vertically. Proof: Mn bisects CD vertically

Certification:
Let Mn ⊥ AB, Mn intersect circle O at m, n
Then Mn must pass the center of the circle
And Mn is the diameter
∵AB//CD
∴MN⊥CD
Ψ Mn vertical bisection CD [diameter bisection perpendicular to chord]

It is known that the center of the ellipse is at the origin of the coordinate, a focal coordinate is (1,0) and the eccentricity of the ellipse is √ 2 / 2

Let the standard equation be X & # 178 / A & # 178; + Y & # 178 / B & # 178; = 1 (a > b > 0)
c=1
e=c/a=√2/2
∴a=√2
And ∵ A & # 178; = B & # 178; + C & # 178;
∴b=1
The standard equation of ellipse is X & # 178 / 2 + Y & # 178; = 1

As shown in the figure, fold one side ad of rectangle ABCD so that point d falls at point F of BC side. AB = 8cm, BC = 10cm are known?

From the properties of folding, we can get: ad = AF = BC = 10, in RT △ ABF we can get: BF = af2 − AB2 = 6, ｜ FC = bc-bf = 4, let CE = x, EF = de = 8-x, then in RT △ ECF, ef2 = EC2 + CF2, that is, X2 + 16 = (8-x) 2, the solution can get x = 3, so CE = 3cm

The two parts of the equation 4x ^ 2-7x-3 = 0 are X1 and x2. Solve the equation and find the value of x2 / (x1 + 1) + X1 / (x2 + 1)

Two of the equations 4x ^ 2-7x-3 = 0 are x1, X2, so X1 + x2 = 7 / 4, x1x2 = - 3 / 4, X2 / (x1 + 1) + X1 / (x2 + 1) = (x1 ^ 2 + x2 ^ 2 + X1 + x2) / (x1x2 + x1 + x2 + 1) X1 ^ 2 + x2 ^ 2 = (x1 + x2) ^ 2-2x1x2 = 73 / 16, so x2 / (x1 + 1) + X1 / (x2 + 1) = (73 / 16 + 7 / 4) / (- 3 / 4 + 7 / 4 + 1) = 101 / 32

As shown in the figure, EF is the median line of trapezoidal ABCD, ah bisects ∠ DAB intersects EF in M, and extends DM intersects AB in n

It is proved that: if ∵ EF is the median line of ladder ABCD, ∵ EF ∥ AB, ∵ EMA = ∵ Nam, ∵ ah bisects ∵ DAB, ∵ EAM = ∵ Nam, ∵ EAM = ∵ EMA = ∵ Nam, ∵ EA = em, ad = 2ae can be obtained, and EM ∥ ab, e is the midpoint of AD, ∵ m is the midpoint of DN, ∵ EM is the median line of △ Dan, ∵ an = 2em = 2ae, ad = an can be obtained

In the following vertical expressions, each letter represents a number from 0 to 9, and different letters represent different numbers
thank you!
（1）seven （2）eleven
+three + seven
+ two + two
————— —————
twelve twenty
（3）FORTY （4）ABCD
+ TEN * EE
+ TEN —————
————— DAFG
SIXTY DAFG
—————
FGGFG

1.
t h r e w o l v s n
1 9 7 2 0 4 3 5 8 6
1 9 7 2 0 6 3 5 8 4
eighty-two thousand five hundred and twenty-six
+ 19722
+ 104
-------
one hundred and two thousand three hundred and fifty-two
perhaps
eighty-two thousand five hundred and twenty-four
+ 19722
+ 106
-------
one hundred and two thousand three hundred and fifty-two
two
Four solutions
t y n e w o l v s
9 1 4 8 2 3 5 7 6
9 1 4 8 2 3 6 7 5
9 4 2 8 3 0 5 6 7
9 4 2 8 3 0 7 6 5