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Seventh grade science competition Volume 2

_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Class (in English)

1. Only one of the following questions is correct. Fill in the letters before the correct answer in the answer sheet (***54 points, 65438+ 0.5 points for each question).

1, scientist Yuan Longping won the highest science and technology award in China in m, and his main research project was ().

A, human genome sequencing B, hybrid rice C, hybrid corn D, cloned sheep

2. The process of angiosperm pollen falling on the stigma is called ()

A, fertilization b, fusion c, germination d and pollination.

3, please analyze, on the moon, which of the following activities is impossible ()

A, laser remote ranging; B, acoustic remote ranging.

C, measure the mass d of the object with a balance, and measure the gravity of the object with a spring scale.

4, insert a red-hot iron bar into cold water, you will see "white gas", this phenomenon shows that water ()

A, chemical reaction with iron b, sublimation.

C, liquefaction d, vaporization and liquefaction.

5. If you cut the corn kernels longitudinally from the center with a blade and drop a drop of iodine solution on the side, the one dyed blue is ().

A, embryo B, radicle C, endosperm D, pericarp and seed coat

6. As shown on the right, a classmate pulls the wooden block placed on the horizontal desktop with force F to slide at a uniform speed. When the front end of the block moves halfway away from the desktop, the change of the pulling force f is ().

A, unchanged B, reduced C, increased D, unable to judge.

7. After the spacecraft enters the predetermined orbit, turn off the engine and run in space. In this spacecraft, the mass of an object is measured with a balance, and the result is ().

A.it is as big as the mass measured on the earth. It is larger than that measured on the earth.

C.it is smaller than that measured on the earth. The mass of an object cannot be measured.

8. The quality of eggs, the thickness of test paper and the speed of sound propagation in the air are about

A.60g 0.8mm 340m/s B.60g 0.8m 340m/s

c . 60g 80 μm 340m/s d . 6g 0.8mm 340km/h。

9. There is a small mirror under the lens barrel of the biological microscope to increase the intensity of light entering the lens barrel. If you can choose the mirror surface of a small mirror, then the best effect is () when using it in biology class.

A. concave mirror B. Convex mirror C. Flat mirror D. Milky white plane

10.in the 1960s, with the rise and development of marine geology, paleomagnetism and geophysics, people created a new global tectonic theory-"plate tectonic theory" on the basis of "continental drift theory". According to the theory of plate tectonics, the formation of the Atlantic Ocean is due to ()

A, the depression of the earth's crust b, the compression of plates c, the collision of plates d, and the extension of plates.

1 1, the following part that we eat does not belong to the vegetative organs of plants is ()

A, sweet potato B, sugarcane C, cucumber D, Chinese cabbage

12, the following animals approach 15 cattle ()

A, a cow B, an ant C, a cat D and an elephant.

Every August, it is the midsummer in China and the Argentine winter in the southern hemisphere.

The reason for this climate difference is ()

A, land and sea distribution b, atmospheric circulation c, landform d, latitude position

14, there is a riddle describing peanuts: "Majia, red curtain, there is a white fat man living in it". Do you know that "hemp room", "red curtain" and "white fat man" in the riddle mean: ()

A, pericarp, seed coat, seed B, pericarp, seed coat and endosperm

C, exocarp, endosperm, seed D, exocarp, endocarp and seed

15, have you seen banana seeds? When you cut a banana, the black spots inside are banana seeds, but these seeds have degenerated. Therefore, people often use the buds grown on banana underground stems to cultivate seedlings, which belongs to ()

A, sexual reproduction b, asexual reproduction c, fission reproduction d, spore reproduction

When 16 and 35℃, people are more prone to heatstroke ().

A, windless and dry desert B, building top C, windy and humid wheat field D, workshop full of steam

17, the number of cells contained in an unfertilized egg is ()

One, one b, two c's, four d's, a lot.

18. When observing the slide with the low power lens of the microscope, a black spot was found in the field of vision. When the slider is moved,

The little black dot does not move; When the eyepiece is turned, the small black dot is still in the same place. The most likely explanation for this phenomenon is ()

A, the aperture is too small b, the eyepiece is not clean c, the reflector is not clean d, and the objective lens is not clean.

19. When the hydrogen balloon hanging an object with a rope rose to the height h, the rope tied to the object suddenly broke.

Then when an object falls to the ground from the highest point, the falling height is ()

A, equal to H B, greater than H C and less than H D, uncertain.

20. The following environmental factors have the greatest and most direct influence on the development of magpie fertilized eggs ().

A, sunshine b, air c, humidity d, temperature

2 1, we can distinguish the sounds of piano and violin because they make sounds: ()

A. different tones; B. different timbres; C. different loudness; D. the frequency is different.

The fuel used in gas lighters can be liquefied with a little pressure. Decompression (opening the valve) is easy to vaporize and burn when it is lit. Do you think the fuel that meets this condition is ()?

A B C D

Chemical name alcohol mercury butane water

Boiling point (℃) 78 357-0.5 65 438+000

Melting point (℃)-117-39-138.40

23, sliding on a horizontal table, the horizontal direction is only affected by two forces with the same three elements, then the block ().

A, kinetic energy must be constant; B, kinetic energy must be increased; C, mechanical energy will inevitably decrease; D, kinetic energy may increase.

24, assuming that there is no atmosphere on the surface of the earth, then people observed the sunrise time compared with the actual atmosphere ().

A will delay B, advance C, keep D, advance in some areas and delay in others.

25, belongs to the solar terms in the following festivals is ()

A, Double Ninth Festival B, Tomb-Sweeping Day C, Dragon Boat Festival D, Mid-Autumn Festival

26, from China's "Tomb-Sweeping Day" to "International Labor Day", the position and moving direction of the sun's direct point on the surface is ().

A, located in the northern hemisphere, moving northward; B, located in the southern hemisphere, moving south.

C, located in the northern hemisphere, and moved south d, located in the southern hemisphere, and moved north.

27. In order to reduce the risk of motorcycle rollover when crossing obstacles, the following statement is correct: ()

A, the front wheel should land first. B, the rear wheel should land first.

C. the front and rear wheels should land at the same time. D. which wheel lands first has nothing to do with the risk of rollover.

28, several students in the playground pole climbing competition, make them up is ().

A, gravity b, friction c, elasticity d, rod tension

29. The focal length of the convex lens may be between10cm and15cm. When the object is away from the convex lens12cm, its image must be ().

A, enlarge B, reduce C, erect D, and invert

30. Pull the same wooden block weighing 5 cows horizontally with a spring scale to make it move in a straight line at a uniform speed on the rough desktop and the desktop with several ballpoint pens. The readings of the spring scale are 4 N and 1 N respectively. The following statement is incorrect: ()

A. This set of experiments can be used to compare sliding friction and rolling friction.

B, when using this group of experiments to study friction, we need to use the knowledge of the balance of two forces.

C, through this set of experiments, it can be concluded that the smoother the contact surface, the smaller the sliding friction.

D. From this set of experiments, it can be concluded that the sliding friction and rolling friction are 4 N and 1 N respectively.

3 1. On the ground, the geosynchronous satellite used for communication is stationary. It takes a week to run: ()

A.24 hours, 23 hours and 56 minutes C. 24 hours and 4 minutes D. 24 hours and 56 minutes

32, the plane flying in a straight line at a constant speed horizontally dropped three balls of the same size, A, B and C, respectively, so the correct picture reflecting the positional relationship of A, B and C in the air is ().

33. As shown in the picture on the right, the beam AB hits the surface of the glass ball and passes through the glass ball after refraction, among which the possible correct light path diagram is ().

a、a B、b C、c D、D

34. A spaceship circled the earth outside the atmosphere after turning off its engine. The possible phenomena in the spaceship are: ()

A. the mass of the object disappears. B. the falling speed of the object becomes faster. C. the candle burns normally.

D. water droplets float in the air in a spherical shape.

Please read the next paragraph and complete questions 35-37.

Da Nan Shan is located in Shekou Peninsula, with an altitude of 336. 15 meters and an area of 3.5 square kilometers. She guarded the Pearl River Estuary, looked at the sea alone, climbed high and looked far, and had a panoramic view of Hong Kong and Shenzhen. The government has now planned it as a forest park. The map on the left below is a topographic map of the Da Nanshan area drawn according to the contour distribution. Please answer according to the map:

35. The ridgeline shown in the figure is _ _ _ _ _ _ _ (fill in the option number).

36. The main reason for the formation of the terrain shown in the figure is _ _ _ _ _ _ _ _ _ _ _ (fill in the option number).

A, internal force action b, flowing water action c, sandstorm action d, wave action

II. Fill in the blanks (*** 16, per space 1 minute)

37. A person stands at the window and looks in the mirror. If he wants to see his image more clearly, he should face the window (choose "his face" or "mirror"). The speed of light in a vacuum is kilometers per second.

38. As shown in the figure, when students heat two substances A and B with the same alcohol lamp, they draw a temperature-time image according to the measurement results. As can be seen from the picture, the substance is crystal.

39. Red blood cells in the human body exchange materials with the external environment.

40. In the imperial palace of the Tang Dynasty, in summer, people in the palace pushed tall waterwheels and sprinkled water on the roof of the palace, and then the water flowed down the roof. It was done at that time.

4 1, a classmate is 1.7 meters tall and stands in front of a flat mirror with a length of 1 meter. When he left the mirror at a speed of 0.5 meters per second, his image in the mirror left him at a speed of _ _ _ _. How does the size of his image in the mirror change? ___________。

42. Nanotechnology is a high-tech science and engineering technology. Nanometer is a very small unit of length, 1 nanometer = 10-9 meters. If the diameter of an atom is 10- 10 meter, arrange _ _ atoms one by one, and the length is one nanometer.

Shops often use box scales to measure the quality of goods (see photo). When weighing, if a piece of mud sticks under the weighing pan, the weighing result is _ _ _ _ (fill in "big" and "small"); If the weight is worn, the weighing result is _ _ _ _ (fill in "big" and "small"); If the position of the zero adjusting nut is slightly to the right than the correct position, the weighing result is greater than the actual mass (fill in "big" and "small").

When Li Ming came home from school, it was windy and rainy. He was running from west to east at the speed of 18 km/h, when he found a strange phenomenon: raindrops fell vertically, so there was wind at this time, and the wind speed was meters per second.

45. The lens of myopia glasses is a lens, which interacts with the part of the eyeball equivalent to the lens and changes the focal length of the eyeball "lens".

46.65438+1At about 2 1 on March 27th, 1999, the U.S. F- 1 17A stealth fighter-bomber prepared to carry out air strikes near Belgrade, Yugoslavia. At this time, the tracking radar of the Yugoslav air defense force Sam-16 air defense missile deployed in this area keeps a close eye on one of the aircraft numbered 806, F- 1 17A, and the launched missile flies at the speed of 830m/s, while F-17A can only fly at the speed of 800. Then it takes only _ _ _ seconds at most from launch to shooting down the plane. This greatly enhanced the fighting spirit of the Yugoslav army and civilians and broke the myth that "stealth planes are invincible"

Third, read the picture analysis questions (*** 15 points)

47. Xiaohong's tap water meter reading was 344 m3 on the 5th of last month. The position of each pointer on the tap water meter on the 5th of this month is shown in the figure. So, she has been drinking water at home for a month.

48. At 7: 45pm local time on May 2, 2003 (the early morning of the 22nd Beijing time), a strong earthquake measuring 6.7 on the Richter scale occurred near Algiers, the capital of Algeria (3 east longitude and 37 north latitude). As of the evening of May 26th, the earthquake has caused 2 162 deaths and 8,965 injuries.

(1) From a global perspective, earthquakes mainly occur in the Pacific Rim and its vicinity. As can be seen from Figure A, Algeria is located in one of the two major earthquake-prone areas in the world.

(2) For the "Beijing time" mentioned in the article, the following description is incorrect (fill in the option number).

A, Beijing time is Beijing local time; B, Beijing time is the time zone of the East Eighth District.

C, Beijing time is the time used in Shenzhen d, Beijing time is east longitude 120? storage period

(3) According to the question and the meaning of Figure A, when the earthquake occurred, Beijing time should be the early morning of 22nd (fill in the specific time).

(4) Earthquake is a natural phenomenon that will bring great disaster to human beings. When an earthquake occurs, the following behaviors are inappropriate (fill in the option number)

A. If you are on the first floor, leave the room quickly and run to an empty place.

B, if the floor is high, quickly hide in the corner of the small room.

C. If it is too late to leave the room, hide under the table.

D, when the earthquake occurs, quickly ran to the window, open the window, call for help.

49. Refrigerators are widely used household appliances. The refrigeration equipment in the refrigerator mainly has three parts: evaporator, air compressor and condenser. The condenser evaporates in the evaporator, and the evaporator absorbs the heat of the freezing chamber to reduce the temperature of the freezing chamber. The air compressor pumps the generated steam away and presses it into the condenser to liquefy it and release the heat brought by the refrigerator. After the condensate is liquefied, it returns to the evaporator, which works circularly, thus keeping the freezing room at a rather low temperature.

(1) According to the working principle of the refrigerator, do you think the main physical properties of the "condenser" in the refrigerator are _ _ _ _ _ _ _ _ _ _ _.

(2) According to the measurement, for every 5℃ increase in the ambient temperature of the refrigerator, the internal power consumption of the refrigerator will increase by 25%. In view of the above reasons, what kind of environment do you think the refrigerator should be placed in when designing home decoration? __________________。

(3) Xiaoming wants to use the refrigerator to lower the room temperature: he opens the refrigerator door first, and then turns on the power. Can he achieve the purpose of lowering the room temperature by doing so? Why?

50. The more frequently paper money is used, the more bacteria there are on the paper. A middle school science and technology activity group randomly collected 30 samples of 8 kinds of banknotes in banks, shops, farmers' markets and hospital toll booths, washed all kinds of banknotes with sterile physiological saline, and cultured the eluate with bacteria, and obtained the following data. Please answer:

(1) It can be inferred from the data that _ _ _

(2) In the process of deducing the above conclusion by using the data in the table, in order to make the conclusion more reliable, it is necessary to compare _ _ _ _ data of banknotes with different denominations (please fill in "total bacteria", "bacteria per sheet" and "bacteria per square centimeter").

Total number of bacteria in naming

(30 tablets) The number of bacteria per tablet.

Number of bacteria per square centimeter (pieces/piece) (pieces /cm2)

2 jiao 126 150 4206 34

5 coke 147400 49 13 34

1 yuan 3631501210568

2 yuan 3631001210367

5 yuan 98800 3293 16

10 yuan 145500 4833 27

50 yuan 25700 857 4

100 yuan 12250 408 2

Four, analysis and calculation (*** 15 points)

5 1. During the festival, hydrogen balloons float into the sky, getting smaller and smaller, and gradually disappear. Imagine what the balloon will eventually look like. Make a prediction based on your physical knowledge and explain the reasons.

Taxi is a convenient means of transportation in city life. According to the taxi invoice map on the right, please find:

(l) What is the average taxi speed during this period (reserved after decimal point 1 bit)?

(2) Assuming that the taxi moves in a straight line at a uniform speed during this period, and the traction of the taxi is known to be 2× 103 N, will the taxi be affected by other forces? If yes, please make a stress analysis diagram (stress diagram).

If you want to learn physics well, you should practice more. Please list two kinds of physical experimental instruments made of large plastic coke bottles, and briefly describe the making process and the physical phenomena demonstrated.

54. March 22nd is World Water Day. Water is the most precious resource for human beings. Please use words or pictures to express natural or applied knowledge related to water (give two examples).

55. The kettle for boiling water at home often has a small hole in the lid. If there is no hole, cover the lid tightly and what will happen if the water boils? Why?

56. Thermometers used by weather stations to measure temperature are installed in shutters. What color is the shutter box? Why? What's the harm if you put it in a closed box? Why? What's the harm if you put it in the open air? Why?