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First, multiple-choice questions (***5 small questions, 3 points for each small question, full score 15 points)
The reciprocal of 1 Equal to ()
A.-2 b.2 c.d Display analysis II. The following operation is correct ().
A.a2+a3=a5 B.a2？ a3 = a5 c .(ab2)3 = ab6 d . a 10÷a2 = a5
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A.B. C. D。
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A. equilateral triangle B. parallelogram C. isosceles trapezoid D. square
Display analysis 5. The daily maximum temperature of a city for five consecutive days in May is 23, 20, 20, 2 1 26 (unit:℃), and the median and mode of this set of data are () respectively.
A.22℃，26℃ B.22℃，20℃ C.2 1℃，26℃ D.2 1℃，20℃
Display parsing
Fill in the blanks (***8 small questions, 3 points for each small question, out of 24 points)
The arithmetic square root of 6.4 is. ★★★★★★★★ Display Analysis 7. Decomposition factor: MX-My = ☆☆☆☆☆ Display analysis 8. In the function, the value range of the independent variable x is. ★★★★★★★ Display Analysis 9. An opaque cloth bag contains two white balls and three yellow balls, all of which are the same except the colors. If they are different from each other, then the probability of touching the yellow ball is. The display analysis is 10. According to the Bulletin of Main Data of the Sixth National Census of Meizhou 20 10 issued by the Municipal Bureau of Statistics, the resident population registered in the 201kloc-0/100 census in the city is about 4.2 million. This number is expressed as human beings in scientific notation. The display analysis is 1 1. As shown in the figure, in Rt△ABC, ∠ b = 90. ED is the middle vertical line of AC, alternating AC and E BC at point D. It is known that ∠ BAE = 30, then the degree of ∠C is. If the length of AB is 8cm, the area of the shaded part in the figure is cm2 ... The display analysis is 13. The diagonal number of convex N polygons is expressed as an(n≥4), for example, a4=2, then:1A5 =; ②a6-a5 =； ③ An+ 1-an =。 (n ≥ 4, expressed by algebraic expression of n) Display analysis
Iii. Answer questions (*** 10 small questions, out of 8 1 point)
14. Calculation:. Display and analysis 15. Simplification: (a+b)2-(a-b)2+a( 1-4b) display and analysis 16. After counting the results of a mock exam in Class 9 (1) of Hedong Middle School,
(1) There are students in this class;
(2) The frequency from 89.5 to 99.5 in this group is, and the frequency is.
(3) It is estimated that the average score of this class's math simulation exam is 17. As shown in the figure, in the plane rectangular coordinate system, point A (-4,4) and point B (-4,0) rotate △ABO 135 clockwise around the origin O, and get △ A 1b65448.
( 1)∠AOB =；
(2) The path length of vertex A from the starting point to A 1 is:
(3) The coordinate of point B 1 is. Display analysis 18. As shown in the figure, point P is on the CD side of parallelogram ABCD, connected with BP, and the extension line with AD intersects with point Q. 。
(1) Verification: △ dqp ∽△ CBP;
(2) When △ dqp △ CBP and AB=8, find the length of DP. The display analysis is 19. As shown in the figure, the image of inverse proportional function and the image of linear function y2=-x+b intersect at point A and point B, where A (1, 2).
(1) Find the values of m and b;
(2) Find the coordinates of point B and write down the range of X when Y2 > Y 1. Display analysis 20. In order to encourage urban residents to save water, a city has set the following water fee standards: when the monthly water consumption of each household does not exceed 20 degrees (1 degree = 1 m3), the water fee is one yuan/degree; When it exceeds 20 degrees, the part that does not exceed is still A yuan/degree, and the part that exceeds B yuan/degree. It is known that a user used 15 degree water for four times, and paid the water fee of 22.5 yuan. In May, the water was used at 30 degrees, and the water fee was paid in 50 yuan.
(1) Find the values of a and b;
(2) If it is estimated that the user's water consumption in June is not lower than that in 60 yuan, but not higher than that in 90 yuan, find the value range of the user's water consumption in June. The display analysis is 2 1. As shown in the figure, in the isosceles trapezoid ABCD, ABCD, AD = BC. After folding △ACD along diagonal AC, point D coincides with the midpoint m of AB side.
(1) Is point C on a circle with a diameter of AB? Please explain the reasons;
(2) When AB=4, find the area of this trapezoid. Display analysis 22. As shown in the figure, it is known that the parabola y=x2-4x+3 intersects the X axis at two points A and B, and its vertex is C. 。
(1) For any real number m, what is the point M(m, -2) on the parabola? Please explain the reasons;
(2) Verification: △ABC is an isosceles right triangle;
(3) Given that point D is on the X axis, is there a point P on the parabola, so that the quadrilateral with vertices B, C, D and P is a parallelogram? If it exists, find the coordinates of point P; If it does not exist, please explain why. . VIP display analysis 23. As shown in figure 1, it is known that the length of line segment AB is 2a, point P is the moving point on AB (P does not coincide with A and B), and AP and PB are taken as positive △APC and positive △ PBD respectively as the same side of side line segment AB.
(1) When the sum of the areas of △APC and △PBD is the smallest, AP =；; (Write results directly)
(2) Connect AD and BC, intersect at point Q, and let ∠AQC=α, then will the size of α change with the moving surface of point P? Please explain the reasons;
(3) As shown in Figure 2, if point P is fixed, rotate △PBD clockwise around point P (the rotation angle is less than 180). Does the size of α change at this time? Just write your guess directly, without proof.
20 10 Physics Examination Paper for Senior High School Entrance Examination in Meizhou City, Guangdong Province
Collect test papers, analyze test papers, display answers and download test papers.
I. Multiple choice questions (*** 12 small questions, 3 points for each small question, out of 36 points)
1. Some energy in nature is difficult to be regenerated once it is consumed, so we should save energy. The following energy, belongs to the non-renewable energy is ().
A. wind energy B. water energy C. solar energy D. oil exhibition analysis II. LED lamp is a new type of high-efficiency and energy-saving light source, and its core component is light-emitting diode. Diodes are made of which of the following materials ().
A. Ceramic materials B. Metal materials C. Semiconductor materials D. Superconducting materials
Display analysis 3. Regarding molecules, which of the following statements () do you think is incorrect?
A. everything is made up of molecules.
B. Molecules never stop moving irregularly.
C. there is interaction between molecules.
D. Some molecules have only attraction, while others have only repulsion.
Display analysis 4. Since March this year, the influenza virus H 1N 1 originating from Mexico has spread rapidly to the whole world. In order to ensure the health of teachers and students, xuwen middle school school canteen insists on high-temperature cooking and disinfection of tableware used by teachers and students. From putting tableware in cold water until it is heated to boiling water, the following related physical quantities about tableware are definitely unchanged ().
A. temperature b volume c mass d density
Display analysis 5. When using household appliances, the following statement is true ()
A. The washing machine uses three hole socket mainly for lightning protection.
B. the refrigerator is placed close to the wall, which is beneficial to heat dissipation.
C. the TV still consumes power when it is in standby mode.
D. The plug of the rice cooker can't be connected to the circuit after being dipped in water, because it is easy to cause the circuit to break.
Display analysis 6. The statement about sound and electromagnetic waves is correct ()
A. Both sound waves and electromagnetic waves can transmit information and both can spread in a vacuum.
B. installing double-glazed windows in houses can reduce the impact of noise on indoors.
C. "Stethoscope" can increase the vibration amplitude and loudness of human heart.
D "voiceprint lock" can only be opened when the owner speaks code, and the main basis for distinguishing sound is tone.
Display analysis 7. Xiao Ming took a photo of the electric energy meter at home, as shown in the picture. After carefully observing the photos, he came to the following conclusion. What you think is right is ().
A. what is the rated power of the watt-hour meter?
What is the calibration current of B watt-hour meter?
C. When taking photos, Xiao Ming's household electricity was 93 16KW? h？
D When taking photos, the electricity used by Xiaoming's family was 93 1.6J?
Display analysis 8. In the following process, the gravitational potential energy of an object is converted into kinetic energy ().
A. the process of paratroopers falling at a constant speed in the air
B. the process of hot air balloon ascending
C. the process of the car driving at a constant speed on a horizontal road.
D. the process of free fall of shot put
Display analysis 9. With the rapid development of the national economy, the living standards of residents have improved significantly, and cars have gradually entered thousands of households. About the physical knowledge of automobile application, the following statement is incorrect ()
A. The rearview mirror can broaden the field of vision and help avoid traffic accidents.
Seat belts are made wider to reduce pressure and ensure safety.
C. When the car brakes suddenly, it will slide for a certain distance due to inertia.
D. the pattern on the car tire is to reduce the friction with the ground.
Display analysis 10. Xiaoyu is pulling a stone with a rope to make a uniform circular motion on the horizontal table. Assuming that all the forces it receives disappear, the stone will ().
A. Do uniform linear motion B. Continue to do uniform circular motion.
C. Fall to the ground D. Stop moving immediately.
Display analysis 1 1. In the circuit shown in the figure, the power supply voltage is constant, and when the K key is closed ().
A. Voltage means smaller, current means smaller, and the lamp is dimmed.
B. The voltage indicator becomes larger, the current indicator becomes larger, and the light becomes brighter.
C. The voltage representation is constant, the current representation is constant, and the brightness of the lamp is constant.
D. The voltage is constant, the current is smaller, and the lamp is dimmed.
VIP display analysis 12. Put an object with a mass of 100g into a measuring cylinder containing 100mL alcohol (known as ρ alcohol =0.8× 103kg/m3). After the object is stationary, the alcohol level rises to the 200mL scale line, so the situation of the object in the measuring cylinder is ().
A. the object sinks into the bottom of the measuring cylinder. Objects float on the surface of alcohol.
C. the object is suspended in alcohol. D. The conditions are not sufficient to determine
VIP display analysis
Fill in the blanks (***6 small questions, 3 points for each small question, full score 18 points)
13. unit and unit conversion: the mass of a blue whale in the ocean is about120t = kg; The mass of a ninth grade boy is about 6×104; The density of marble used in our classroom floor is about 2.7× 103. The display analysis is 14. Xiaoming made an electromagnet by winding a wire around a nail and connecting it to the circuit as shown in the figure. Close the switch S, and the left end of the small magnetic needle should be the pole when it is stationary. When the slider P of the sliding rheostat moves to the left, the magnetism of the electromagnet will be displayed. Analysis 15. As shown in Figure A, it is a surveillance camera installed at many intersections in modern cities, which can take photos of the scene when driving illegally or causing traffic accidents. The lens of a camera is equivalent to a lens, and its working principle is similar to (camera, projector or magnifying glass can be selected). Pictures B and C were taken continuously after a car and a bicycle collided while passing through the intersection.
Display analysis 16. The picture shows an experimental device for measuring the mechanical efficiency of the pulley block, with a total hook weight of 6n.
(1) During the experiment, the spring dynamometer should be pulled vertically upward. According to the figure, the tension is n, if the hook code rises to 8cm, the spring dynamometer will move up by cm, and the mechanical efficiency of the pulley block is 0.
(2) If only the number of hook yards is increased, the pulley block will have mechanical efficiency. (optional: increase, decrease or unchanged) VIP display analysis 17. Wuliangye, a famous liquor in China, is known as "three cups refreshing, one drop touching the lips", and has won two gold medals in the World Expo. There is exquisite Wuliangye on the box. If this bottle is filled with water, its total mass will be more than kilograms when it is filled with wine. The display resolution is 18. As shown in the figure, it is a simple schematic diagram of the principle of electric water heater. The water heater can be heated or kept warm by the switch S, and when the switch S is closed, the water heater is in a state. After the water in the water storage bucket of the water heater is filled to the highest water level, the mass of the water in the bucket is 10kg, so the water is heated from 28℃ to 98℃. ℃), the calorific value of coke is 3.0× 107 J/kg]. VIP display analysis
Third, answer questions (***9 small questions, out of 46 points)
19. As shown in the figure, the metal ball is immersed in the bottom of the container filled with water and is acted by three forces. Try to draw a schematic diagram of its force in the picture. Display analysis 20. The train has two toilets at the back of the carriage. Only when the doors of both toilets are closed (the latch of each door is equivalent to a switch) will the indicator light in the notice board in the carriage light up and the notice board will display "The toilet is occupied". Remind passengers that two toilets are occupied. Please connect the symbols of each component in the drawing into a circuit diagram that meets the above design requirements. Display analysis 2 1. In the experiment to explore the law of temperature change during solid melting, students in an experimental group drew an image as shown in the figure according to the measured data.
(1) It can be seen from the image that the melting point of the substance is℃, and at the end of the second minute, the substance is in (fill in "solid", "liquid" or "solid-liquid * * state").
(2) The melting process of this substance is characterized by continuous heat absorption, and the temperature and internal energy increase.
(3) Comparing the AB section and the CD section in the figure, it can be seen that if the temperature increases to the same extent, this section absorbs more heat. Display analysis 22. As shown in the figure, the experiment of "exploring the imaging law of plane mirror" is carried out. Put a ruler under the vertical transparent glass plate, and the ruler is vertical to the glass plate; Two identical candles A and B stand on the straightedge on both sides of the glass plate, with candle A as the imaging object.
(1) In order to facilitate observation, the experiment should be carried out in (choose "bright" or "dark") environment; In addition, the transparent glass plate is used instead of the flat mirror, although the image is not as clear as the flat mirror, the candle image A can be observed at the same time, which skillfully solves the problem of determining the position and size of the image. If there are thick glass plates and thin glass plates, glass plates should be selected in the experiment.
(2) Light the candle A, carefully move the candle B until it coincides with the image of the candle A, and then find the size of the image and the object; Further observing the position of candles A and B on the ruler, we can find the distance between the image and the glass plate.
(3) Take off the candle B and put a visor in its original position. The image of a candle (filled with "energy" or "can't") is displayed on the light screen, indicating that the object is in the plane mirror (filled with "real" or "imaginary").
(4) Which of the following actions do you think should be taken to confirm whether the above imaging features are reliable ()?
A, keep the position of two candles A and B unchanged, and change the position of the glass plate for observation for many times;
B, keeping the position of the glass plate unchanged, changing the position of the candle A for many times, and performing the same operation as the above (2). . VIP display analysis 23. Zhou Xiao designed and connected the physical connection diagram as shown in the figure when doing the experiment to explore the relationship between current and resistance.
(1) Please draw the corresponding circuit diagram according to the physical connection in the question.
(2) In the experiment, Zhou Xiaoxian connected the 5 Ω resistor R to the circuit, and the circuit connection was completely correct. After he adjusted the resistance of the sliding rheostat to the maximum, he closed the switch S, directly read the instructions of the ammeter, and recorded the data in the table. Then he replaced the 5 Ω resistor with10 Ω resistor and 20 Ω resistor respectively, and repeated the above operation. His mistake in the experimental operation is that he didn't keep the resistance r constant.
(3) Zhou Xiao re-conducted the experiment after discovering the error, and the data obtained are shown in the following table. According to the experimental data in the table, the conclusion is: 20 10/0 chemistry test paper for the senior high school entrance examination in Meizhou City, Guangdong Province.
Collect test papers, analyze test papers, display answers and download test papers.
First, multiple-choice questions (this question contains 15 questions, each with 2 points and * * 30 points. There is only one option in each question.
1. The "stone paper" used by the National People's Congress and NPC deputies this year is made of calcium carbonate as the main material and through special processing. Calcium carbonate belongs to ().
A. oxide B. acid C. base D. salt display analysis II. The following changes in daily life, which is different from the other three categories is ()
A. Melting of snow and ice B. Grape brewing C. Grain mildew D. Fireworks explosion
Display analysis 3. Our food, clothing, housing and transportation are inseparable from various substances. Among the following materials, the organic synthetic material is ()
A. cotton plastic cement steel
The "poison" in the idiom "drinking poison to quench thirst" refers to the wine with arsenic added. Arsenic is an oxide (As) of arsenic, which is very toxic. The valence of arsenic in arsenic is +3, so the chemical formula of arsenic is ().
A.As2O B AsO C As2O 3D as O2
Display analysis 5. "Gold, silver, copper, iron and tin" are commonly known as hardware. Among these five metals, one metal can react with the salt solutions of the other four metals. This metal is ().
A. gold, copper, iron and tin
Display analysis 6. When a car is hit by a certain force, the substances in the airbag will decompose rapidly, and the gas with the most content in the air will be generated, so that the airbag will pop up and expand rapidly, and the safety of people on the car will be protected. The gas is ().
A.N2 carbon dioxide helium
7. A classmate has symptoms of diarrhea, and the doctor advised him not to eat food rich in oil and protein for the time being, so the breakfast he should choose is ().
A. eggs and milk B. steamed bread and porridge
C. Fried dough sticks and soybean milk D. Fried chicken pieces and yogurt
Display analysis 8. After mixing and grinding the following substances with hydrated lime powder, it is () that can smell pungent smell.
A.k2co 3 B . CO(NH2)2c . NH4Cl D . Ca3(PO4)2
Display analysis 9. The following method to deal with the accident is correct ()
A. When household appliances catch fire, put them out with water immediately.
B. When there is a fire in the room, immediately open the doors and windows for ventilation.
C. When the frying pan is on fire, water it immediately to put out the fire.
D. when putting out forest fires, set up isolation belts.
Display analysis 10. The following practices will not cause food harm to human health ()
Baking soda is baking powder used to bake cakes.
B. Fumigate tremella, vermicelli and other foods with sulfur.
C, using formaldehyde solution as preservative for edible aquatic products.
D, pickling food with industrial salt containing sodium nitrite.
Display analysis 1 1. The following substances have been exposed to air for a period of time, and their mass has increased due to chemical changes ().
A. concentrated hydrochloric acid B. concentrated sulfuric acid C. sodium chloride D. quicklime
Display analysis 12. A deflated ping-pong ball will swell up when it is put into hot water because of the gas in the ball ()
A. the spacing between molecules increases. The volume of molecules increases.
C. The number of molecules increases D. The mass of molecules increases.
Display resolution 13. The following experimental operation is correct ()
A.
Put out the alcohol lamp B.
Liquid reading
C.
Sodium hydroxide solid weighing.
Determine the pH value of the solution
Display analysis 14. The following understanding of "chemistry and life" is wrong ()
A. use gasoline to remove oil stains from clothes.
B. Excessive intake of trace elements is not good for your health.
C. Use more water in daily life to save water resources.
D, garbage classification and recycling, open burning.
Display resolution 15. The identification method of the following substances is correct ()
A. distinguish oxygen from nitrogen by observing color.
B, filtering to identify distilled water and sucrose water.
C. calcium chloride solution is used to distinguish sodium carbonate solution from calcium hydroxide solution.
D, identifying hydrogen and carbon monoxide with clarified limewater.
Display parsing
Fill in the blanks (this question includes 6 small questions with ***35 points)
16. Life is full of science, and you can study anywhere. Common substances are: ①SO2, ②C2H5OH, ③NaOH, ④NaCl, ⑤C, ⑤ ⑥CH3COOH ... Please fill in the serial number of the appropriate substance in the blank:
(1) commonly known as caustic soda is.
(2) What is used to prepare physiological saline in medical treatment?
(3) One of the air pollutants is.
(4) It can be used as the electrode of dry battery.
(5) The acid contained in vinegar is.
(6) Display analysis 17 can be used as the fuel of alcohol lamp. Aluminum is the most abundant metal element in the earth's crust and is widely used in production and life. The schematic diagram of aluminum atom structure is as follows.
Please answer:
In the (1) diagram, the value of x is, and the number of protons in the nucleus of aluminum atom is.
(2) Aluminum has good corrosion resistance, because (expressed by chemical equation), the display analysis is 18. "Greenhouse effect" is one of the environmental problems studied at Copenhagen Climate Change Conference, and CO2 is the highest greenhouse gas in the atmosphere at present.
(1) Write down two uses of carbon dioxide.
(2) Among the following measures, (fill in the serial number) is conducive to reducing the concentration of CO2 in the atmosphere.
① Encourage public transportation and advocate a low-carbon life.
② Vigorously develop thermal power generation.
③ Adopt energy-saving technology to reduce the consumption of fossil fuels.
(4) Development and utilization of new energy sources such as solar energy and wind energy.
(3) In order to reduce CO2 emission, another method is to convert CO2 into organic matter and realize carbon cycle. For example, CO2 reacts with H2 under the conditions of catalyst and heating to generate methane and water. The chemical equation of this reaction is. Display and analysis 19. The label of a natural mineral water has the following words: "The main component of water quality (mg/L): K+0.62-3.25 Na+18.7-29.8c2+17.8-26.2cl-14.2-30.8 sulfate 4/.
The chemical symbol of (1) sulfate ion is: the meaning of the number "2" in "Ca2+" is.
(2) Mineral water is obvious (fill in "acidic", "alkaline" or "neutral").
(3) Distinguishing between soft water and hard water in daily life can reduce the hardness of water. The solubility curves of two solid substances X and Y are shown on the right. Answer the following questions:
(1) From the solubility curves of X and Y, the solubility is greatly influenced by temperature.
(2) At 40℃, the solubility of Y is g; At 60℃, add 45g of X into 50g of water and fully dissolve it. The aqueous solution of X at this temperature is (saturated or unsaturated).
(3) The method of extracting Y from the saturated solution of Y is (fill in "cooling crystallization" or "evaporating solvent"). The analysis shows that 2 1. A ~ H is a common substance in junior high school chemistry. It is known that A is a black solid element, G is a purple solid element, B is a reddish-brown powder, and F is a black powder. Their transformation relationship is shown in the following figure.
Please answer:
The chemical formula of (1)B is, and the chemical formula of f is.
(2) Of the three substances A, C and E, the reducing one is (fill in chemical formula).
(3) The chemical equation of reaction ① is: Write a chemical equation that can realize reaction ③.
(4) The basic types of chemical reactions involved in reactions ① ~ ④ are,, display and analysis.
Three, short answer (this question contains two small questions, ***2 1 minute)
22. The picture below shows the experimental devices commonly used in laboratories. Please answer the relevant questions:
(1) Device C consists of catheter and (insert instrument name).
(2) The chemical equation of preparing O2 with H2O2 and MnO2 in the laboratory is, and the selected generator is (fill in the serial number, the same below); If KClO3 and KCl O3 are used
When MnO2 is used to produce O2, the selected generator is.
(3) The chemical equation for preparing CO2 in the laboratory is: If HCl and H2O are mixed in the prepared CO2, NaOH solid is used to remove impurities during purification. Do you think this method (fill in "feasible" or "infeasible") is because.
(4) The acquisition device for preparing H2 in the laboratory is or. Display and analysis. A chemical interest group explored whether the reaction between NaOH solution and dilute hydrochloric acid was accurate and complete. Please participate in their exploration activities and answer relevant questions.
Experimental inquiry:
(1) Scheme 1: A student first adds about 2mL NaOH solution to the test tube as shown on the right, and then drops a few drops of phenolphthalein solution, and the solution turns red. Then, slowly add dilute hydrochloric acid and shake it while dripping until the solution just changes color, which proves that NaOH solution and dilute hydrochloric acid just react completely.
Please point out the mistakes in the operation on the right.
② Write the chemical equation of the reaction between NaOH solution and dilute hydrochloric acid.
(2) Scheme 2:
Experimental steps, conclusions of experimental phenomena
Take 2mL NaOH solution in a test tube, drop a certain amount of dilute hydrochloric acid, shake and add magnesium bars. If the dilute hydrochloric acid is excessive,
If there is no obvious phenomenon, NaOH solution and dilute hydrochloric acid react completely.
Experimental reflection:
(3) In the first scheme, if a small number of bubbles are observed in the process of dropping dilute hydrochloric acid, the reason for bubbles may be (write one at random).
(4) Some students suggested that the second scheme could not prove that NaOH solution reacted with dilute hydrochloric acid completely, because.
Extend the application:
(5) Please illustrate the application of neutralization reaction in production and life.
Fourth, the calculation problem (this problem contains 2 small questions, *** 14 points)
24. Fertilizer plays an important role in increasing crop yield, and ammonium nitrate is a fertilizer with high nitrogen content.
The mass ratio of nitrogen, hydrogen and oxygen in (1)NH4NO3.
(2) 2) The mass fraction of nitrogen in NH4NO3 is.
(3) In order to ensure that crops can get 70g of nitrogen, at least GnH4NO3 should be applied.
physical quantity
Experiment times resistance r
(ω) current I
(1)
1 5 0.48
2 10 0.24
3 20 0. 12
(4) Zhou Xiao found a small light bulb, so he replaced the resistance of 20 Ω with this small light bulb, and he continued the experiment. As shown in the figure, the resistance of the small bulb is ω. Display analysis 24. Incandescent light bulbs can be seen everywhere in life. If we look closely, we will find that everyone has learned a lot about physics. Please complete the following questions:
(1) When an incandescent bulb emits light normally, the current will be converted into internal energy and light energy when it works through the filament.
(2) After long-term use, the brightness of incandescent bulbs is darker than when they were newly bought, because the filament is heated (fill in the name of state change), the resistance becomes larger, and the actual power of the bulbs (fill in "bigger", "smaller" or "unchanged").
(3) The light emitted by incandescent bulbs follows the law of light in all directions. Display analysis 25. Briefly describe the relationship between fluid pressure and flow velocity. If it is an aircraft wing model as shown in the figure, please briefly explain the reason why the aircraft gets upward lift. Display analysis 26. As shown in the figure, the mass of object A is m= 12kg. Under the action of the pulling force F, the object A moves in a straight line at a uniform speed on the horizontal plane at a speed of 0. 1m/s, and the pointer of the spring dynamometer is 12N, ignoring the friction between the pulley and the rope and the gravity on the pulley, the spring dynamometer and the rope, and the rope is long enough.
(1) The magnitude of the friction force f between the object A and the horizontal plane;
(2) the magnitude of the pulling force f;
(3) The work done by the pulling force F to 10s during the movement of object A.. . VIP display analysis 27 As shown in the figure, it is a device for lifting heavy objects by DC engine. It is known that the weight of the heavy object is m=50kg, the power supply voltage U= 1 10V is constant, and the motor coil resistance R = 4Ω, regardless of friction everywhere. When the motor is lifted upward at a certain speed, the motor will be lifted upward at a constant speed.
Q:
(1) power output power;
(2) heating power of motor coil resistance r;
(3) Try to find the rising speed of heavy objects from the perspective of energy transformation and conservation. . VIP display analysis
25. In industry, sodium hydroxide, chlorine gas and H2 are prepared by electrolytic sodium chloride solution. The chemical equation of the reaction is: 2NaCl+2H2O2NaOH+H2↑+Cl2↑. H2 =+Cl2 =。 Now a certain mass fraction of 2 14.6g NaCl solution is electrolyzed. When NaCl is completely reacted, 0.4gH2 is generated.
(1) When the NaCl reaction is complete, the mass of Cl2 produced is g, and the mass of NaCl participating in the reaction is g. 。
(2) What is the mass fraction of solute in NaOH solution after the complete reaction of NaCl? (Assuming that all generated Cl2 and H2 escape)