Science review materials and examination papers in the second volume of the sixth grade of primary school

First unit

1. Under the action of force, a hard rod that can rotate around a fixed point like a screwdriver and pry up a heavy object is called a lever.

2. The position that supports the lever so that it can rotate around it is called fulcrum, the point where the lever is stressed is called dynamic action point, and the point that hinders the movement of the object is called resistance action point.

3. The distance from the fulcrum to the resistance point is less than the distance from the fulcrum to the force point, which is a labor-saving lever, and the distance from the fulcrum to the resistance point is greater than the distance from the fulcrum to the force point, which is a laborious lever; When the distance from the fulcrum to the resistance point is equal to the distance from the fulcrum to the force point, the lever is neither labor-saving nor laborious.

Balance is an instrument used to measure the mass of an object, which is made according to the principle of lever balance.

More than 3,000 years ago, China had used leverage to mash grain and pump water from wells.

6. Under the action of force, the lever is in equilibrium or swings slowly, which is called lever balance.

7. The steelyard is made by using the principle of lever balance.

8. The pulley fixed on the bracket is called crown block, and the pulley moving up and down with the weight is called moving pulley.

9. The function of crown block is to save energy but change the direction of force, and the function of moving pulley is to save energy but not change the direction of force; The function of pulley block is to save energy and change the direction of force.

10. The simple machine at the top of the flagpole belongs to the crown block.

1 1. Axle is the deformation of lever, with the force point on the wheel and the resistance point on the axle.

12. For a screwdriver, the handle of the screwdriver is a wheel and the rod of the screwdriver is a shaft; For the general axle, the big circle is called the wheel, and the small circle is called the shaft.

13. The bigger the wheel of the axle, the more labor-saving. When the wheel drives the axle, it is more labor-saving. The more important officials drive the wheels, the less effort they have.

14. The wheel with teeth on the edge is called a gear, which plays the role of transmitting power.

15. The big gear drives the small gear, which makes the rotation speed faster, but it is laborious. The pinion drives the big gear, which slows down the rotation speed, but saves labor.

16. The function of inclined plane is to save labor. The greater the slope of the inclined plane, the more labor is consumed, and the smaller the slope, the more labor is consumed.

17. The screw uses the inclined plane principle, which saves labor. Spiral is a deformed slope, which can save labor.

18. The common simple machines we have learned are levers, pulleys, axles, ramps, gears and so on.

19. Bicycles were invented at the beginning of 19 century. It is not only used as a means of transportation and fitness tools, but also an important tool in many sports. The earliest bicycle was a wooden bicycle invented in 18 13.

20. The components of a variable-speed bicycle include a big gear, a small gear, a chain and a pedal crank.

2 1. Power can be transmitted from one gear to another, and they rotate in opposite directions. The pinion rotates faster than the big gear.

1, talk about the law of leverage balance.

Law of lever balance: number of squares on the left side of lever ruler × number of hook codes = number of squares on the right side × number of hook codes.

Or: resistance× resistance arm = power× power arm.

2. How is the power of bicycle transmitted?

Power transmission process of bicycle: pedal → gear → chain → pinion → rear wheel.

3. When riding a bicycle, how is the power transmitted to the rear wheel?

The front wheel rotates, transmitting power to the chain, the chain drives the rear wheel to rotate, and the big gear drives the pinion to rotate.

4. How can the gears of the variable-speed bicycle run faster with the bicycle?

The big and small gears at the back run faster with the bike.

5. Where is the simple machine used on the bike? What is its function? Fill in the table below

The role of bicycle parts with simple mechanical types

The pedal shaft rotates quickly.

Steering and balance of handlebar and axle

Brake lever, pulley and axle brake, saving labor.

Chains and gear shafts change the speed at which wheels rotate.

The inclined plane of the car seat saves labor (decompression)

The bolts of the front axle and the rear axle are fixedly connected in a spiral way.

6. Where is the simple machine used in life, and point out what kind of simple machine it belongs to.

What kind of simple machines are used in life examples?

Scissor lever

Crane pulley

Steering wheel shaft

Four-wheel drive gear

Axe bevel

Second unit

1, the ocean area accounts for more than 70% of the total area of the earth.

2. Among the water resources on the earth, salt water accounts for 97.5% and fresh water accounts for 2.5%.

3. In fresh water, 99.7% is difficult to use, and only 0.3% of rivers, lakes and shallow groundwater can be used by human beings. Therefore, the water resources available for human beings on the earth are less than one tenth of that of fresh water.

4. The state has clearly stipulated that red brick will quit the historical stage in 2008.

5. Land resources include cultivated land, grassland, woodland, wetland, desert and construction land.

6. Cultivated land is the main place where we grow food, and the decrease of cultivated land makes the world food shortage more severe.

7. The total cultivated land area in China is 6.5438+0.2339 million hectares, which is 2.53 million hectares less in 2003 alone, equivalent to the area of more than 3.6 million football fields.

8. The per capita arable land in China is 0.095 hectares, which is less than half of the world's per capita. China has a large population and less arable land per capita, which is the basic national condition. We rely on only 7% of the world's arable land to feed 23% of the world's population, which shows how precious China's land resources are!

Yuan Longping, a Chinese scientist and "father of hybrid rice", successfully used wild rice to study hybrid rice, thus alleviating the contradiction of world food shortage.

10. At present, there are more than 2 million biological species on the earth, but human activities have seriously affected the survival of wild animals and plants. At present, 5% ~ 20% of vertebrate and tree species are threatened with extinction, and the rate of species extinction is increasing at a hundredfold rate. By 2003, there were only about 100 wild giant pandas in the world, which were on the verge of extinction. There are hundreds of endangered wild animals in China, such as golden monkey, Chinese sturgeon, Chinese alligator, baiji dolphin and red-crowned crane. From the perspective of ecological balance and biodiversity, the extinction of any species will bring unpredictable consequences to the survival and continuation of other species.

1 1. In order to protect wild animals, we must protect their living environment, so we should establish nature reserves.

12. There are some minerals with mining value on the earth.

13. Mineral resources are one of the indispensable natural resources for human life and production. Mineral resources are mainly divided into metallic minerals and nonmetallic minerals.

14, steel is made of iron ore by smelting. Iron ore is smelted in a furnace. Hot metal is discharged for steelmaking, and molten steel is discharged into steel.

15, China is rich in iron ore resources and widely distributed. Liaoning, Sichuan and Inner Mongolia all have large iron ore plants and iron and steel smelting plants.

16. Common iron ores are hematite, limonite and magnetite.

17. Non-metallic minerals include energy minerals, such as oil, coal and natural gas, and other non-metallic minerals, such as timely, graphite, asbestos and diamonds.

18, energy minerals take a long time to form, so energy minerals are non-renewable energy.

19, fishery resources are renewable resources, but overfishing will cause the depletion of fishery resources and the collapse of fishery production.

20. In the vast ocean, there are 1.7 million kinds of marine animals and 25,000 kinds of marine plants. Scientists estimate that about 9,000 kinds of fish are caught, and 70% of the fishing grounds in the world are overfished.

2 1. In the ocean, in addition to abundant marine fishery resources, there are also extremely rich treasures in the depths of the ocean. The bottom of the sea is a huge treasure house. Among the minerals in the seabed surface, there are metal minerals such as manganese, iron, copper, nickel and cobalt, which are very useful for industry. The reserves of these metal minerals on the seabed are much more than those on land. Among the minerals under the sea floor, in addition to oil and natural gas, coal mines with large reserves have also been discovered.

22. Red bricks are made by sintering clay excavated from cultivated land. At present, more than 84% of building wall materials in China still use traditional clay solid bricks, which consume 600 billion pieces of red bricks every year. It is estimated that every production of 6.5438+0.000 red bricks will consume about 654.38+0.65438+0.000 square meters of cultivated land.

23. Since16th century, about 150 species of birds, 100 species of mammals and nearly 100 species of amphibians and reptiles have become extinct.

24. In Wolong Nature Reserve, there are more than 3,000 species of plants, such as Sichuan redwood and Davidia involucrata.

25. Seawater contains a lot of salt. In addition to being edible, sea salt can also be processed into chemical raw materials.

26. Water resources in China: more in the south and less in the north; There are many in the east and few in the west; There are more summer and autumn, less winter and spring, and the annual change rate is large.

27. The most abundant runoff is in Asia, followed by South America; The poorest water resources are Africa and Asia; The country with the richest water resources is Brazil, and China ranks sixth.

Short answer

1. What do you think of the dripping phenomenon of faucets in public places? What would you do?

It is sad to see that water resources are wasted. We should turn off the tap and publicize the importance of saving water resources.

2. How do you feel when you see the destruction of cultivated land by digging holes and taking soil?

It pains me to see the situation of digging holes and taking soil to destroy cultivated land. I want to publicize the importance of land resources and call on people to cherish every inch of cultivated land.

3. Why are red bricks banned?

At present, more than 84% of building wall materials in China are still using traditional clay solid bricks. China consumes 600 billion red bricks every year. Destroyed a lot of cultivated land.

4. Why should we cherish water resources?

The ocean area accounts for more than 70% of the total area of the earth; Among the water resources on the earth, salt water accounts for 97.5% and fresh water accounts for 2.5%; Of the fresh water, 99.7% is difficult to use, and only 0.3% of rivers, lakes and shallow groundwater can be used by human beings. The water resources on the earth are less than one tenth of the fresh water available to human beings.

5. Tell me about Yuan Longping's contribution?

Yuan Longping successfully developed hybrid rice based on wild rice, which eased the contradiction of world food shortage.

6. Which projects are refined and processed from petroleum?

Gasoline, diesel oil, lubricating oil, asphalt, wax, plastic, chemical fiber, etc.

7. How is oil formed?

Paleontology multiplied in large numbers, was buried by sediments after death, and formed oil after a long geological process.

8. What are the main products of offshore fishing in China?

There are large yellow croaker, small yellow croaker, prawn, squid, hairtail, jellyfish, olive crab and so on.

9. Why do you want to stop fishing?

Protect fishery resources and increase the catch.

10. What are the endangered animals and plants in China?

Endangered animals in China include giant pandas, golden monkeys, Chinese alligators and baiji dolphins. Endangered plants include Metasequoia glyptostroboides, Ginkgo biloba, Davidia involucrata and aromatic fruit trees.

1 1. What measures have been taken to protect rare animals and plants in nature reserves?

In nature reserves, people have taken measures such as banning farmland reclamation, cutting down trees, hunting and mountain fires, providing a natural environment for all kinds of animals and plants to survive.

12. Give examples to illustrate what land resources are.

Cultivated land, grassland, woodland, wetland, desert and construction land are all land resources.

13. What are the nonmetallic minerals?

Non-metallic minerals include energy minerals such as oil, coal and natural gas, as well as minerals such as graphite, asbestos and diamonds.

14. The following is the situation of energy and minerals in the world. Write down the inspiration you get from the data in the table.

Proven reserves of energy and mineral resources: annual world production and future exploitable time (years)

Petroleum1845t 4.5t 4 1

Natural gas 1760 trillion cubic meters 3 trillion cubic meters 586

2 trillion tons of coal, 4 billion tons and 50 billion tons.

Enlightenment: There are not many energy and mineral reserves on the earth, and they are non-renewable energy. In a few decades or hundreds of years, the oil, natural gas and coal on the earth may be used up. So we should protect and save these resources, and at the same time we should develop other new energy sources.

15, the fresh water available to human beings on the earth is less than one in ten thousand. What do you think of this?

Idea: Fresh water available for human use on the earth is extremely scarce. To protect water resources and save water, we should start from me, from now on, and from the little things in life.

Third unit

1. The solar system consists of the sun, eight planets and their satellites, asteroids, comets, meteors and other celestial bodies.

2. As the central celestial body of the solar system, the mass of the sun accounts for more than 99% of the total mass of the solar system. Eight planets revolve around the sun, and satellites revolve around their own planets.

The sun is the only star in the solar system that can emit light and heat.

Jupiter is the most massive planet in the solar system, and its volume is 1320 times that of the earth. Its surface is composed of gas and its interior is liquid.

5. Comet ice and dust. When it runs near the sun, its tail will drag a long tail.

6. A large number of asteroids in the solar system, most of which are in orbit between Jupiter and Saturn.

7. When the aggregate of rocks and dust in space enters the earth's atmosphere, the heat generated by friction with the atmosphere makes it burn, thus forming a twinkling meteor in the sky.

8. The eight planets are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune from near to far. Among them, Mercury is closest to the sun, Neptune is farthest from the sun, Jupiter is the largest and Mercury is the smallest.

9. Mars is one of the main targets for human beings to explore the alien world in recent years. At the beginning of 2004, the American "Spirit" probe landed on Mars, once again focusing on the eyes of the world.

10, the Milky Way is a very large celestial system, including hundreds of billions of stars and many nebulae in the form of clouds. It looks like a whirlpool in the top view and a discus in the side view.

1 1, the speed of light propagation is about 300,000 kilometers per second, and the distance of light propagation in one year is called 1 light year. 1 light-year is 94605 billion kilometers.

12, the diameter of the solar system is 0.00 1, the diameter of the Milky Way is about 65438+ million light years, and the sun is about 23000 light years away from the center of the Milky Way.

13. Outside the Milky Way, astronomers have discovered billions of galaxies similar to the Milky Way, which are called extragalactic galaxies.

14. Astronomers refer to the Milky Way and all observed extragalactic galaxies as total galaxies. The whole galaxy is only a small part of the universe. Now radio telescopes can observe the space outside 65.438+0.5 billion light years, but the edge of the total galaxy has not been found yet.

15. For people in the northern hemisphere, Andromeda is an extragalactic galaxy visible only to the naked eye. Its diameter is1600 million light years, with 400 billion stars and a distance of 2.5 million light years.

16. In order to understand the starry sky, the ancients divided the whole sky into 88 regions according to the patterns and myths and legends formed by a group of bright stars in the sky, and each region was a constellation. Usually we can only see part of the all-sky constellation, and the starry sky we see in different seasons is different.

17, the stars in the sky are big and small, bright and dark. These stars seem to be as far apart, but in fact they are far apart.

18, the representative constellations in spring are Leo, Aries and Ursa Major; The representative constellations in summer are Cygnus, Aquila and Lyra. The representative constellations in autumn are Cepheus, Andromeda and Pegasus. The representative constellations in winter are Orion, Taurus and Canis major.

19, Polaris is located at the end of Ursa minor and is the brightest star in Ursa minor. The North Star can be found by using the Big Dipper, which extends the bucket side of the Big Dipper by about 5 times. At this time, the star you see is Polaris. If you can't see the Big Dipper, you can also find the North Star through Cassiopeia (arranged in a W shape).

In the 20th and early 20th centuries, Renault invented the radio telescope, and humans began to receive radio waves from the universe. 1926, American Goddard invented the liquid propellant rocket, which opened a new era for mankind to step into space. 1957, the Soviet union launched the first artificial earth satellite; 1969, Apollo 1 1 landed on the moon.

2 1 and1In the 6th century, Copernicus put forward the "Heliocentrism", which completely overthrew the "geocentric theory" and laid the foundation of modern astronomy. /kloc-in the 0/7th century, Galileo invented the astronomical telescope, and the lunar crater was presented to people.

22, 1970, China's first artificial earth satellite was successfully launched; 1975, China's first recoverable satellite returned to the ground safely; In 2003, Chinese astronaut Yang Liwei traveled in space and became the first "astronaut" in China. His spaceship is Shenzhou 5.

23. The Summer Triangle refers to Vega, Altair and Tianjin IV.

24. In A.D. 140, Ptolemy, an ancient Greek astronomer, put forward the theory of "geocentric theory", holding that the earth is the center of the universe.

25. Bruno developed Copernicus' theory and further pointed out that the sun is not the center of the universe, and the universe is infinite.

26. Space breeding is a scientific experiment conducted in space. It carries crop seeds on a recoverable ground satellite, and with the help of unpredictable environmental changes on the ground, such as ultra-vacuum in space, microgravity and cosmic rays, the seeds are mutated, and stable genetic traits are obtained through generations of ground breeding, thus cultivating new agricultural varieties.

27. Using recoverable satellites and manned spacecraft to carry out scientific experiments in space for the benefit of mankind can achieve unexpected results under certain circumstances.

28.20071October 24th, 10, China's first lunar exploration satellite "Chang 'e-1" was successfully launched.

29. All the objects in the spaceship are in a state of weightlessness.

30. We mainly look for the North Star according to the Big Dipper. It belongs to Ursa major and Polaris belongs to Ursa minor.

Second, short answer questions

1 for example, the relationship between space science and our lives.

The application of space science is mainly in communication, navigation, geodesy, meteorological observation, remote sensing and other fields. For example, cell phone calls, spacecraft flying into the sky, high-altitude geodesy, weather forecasting, and research on the moon and Mars are all inseparable from space science.

2, the method of observing the starry sky.

(1) Use a compass or other methods to determine the orientation, and the person faces north.

② Match the star map with the actual starry sky direction.

(3) Use a set of red cellophane flashlight light sources to identify the constellation against the star map.

3. What are the ways to find Polaris?

Method 1: Facing the northern sky, the brighter star that extends the side of the Big Dipper by about 5 times is Polaris.

Method 2: use Cassiopeia (arranged in a W shape) to find;

Method 3: ① People face due north (determined by compass); ② Face north with a small paper tube, and tilt the local latitude angle upward from the horizontal plane (Le 'an is about 27 north latitude). At this time, the bright star facing the paper tube is "Polaris".

4. How to observe the constellation?

The way to observe the constellation is to determine the direction first, and then find a bright star as a sign. Standing in a fixed position at a fixed time every day, looking for a reference.

5. Mir Space Station.

Mir space station is the third generation space station of Soviet Union/Russia and the first permanent space station in the world. Many scientists have carried out many scientific experiments here that cannot be completed elsewhere.

6. Talk about the relationship between the solar system, the Milky Way and the universe.

The universe includes the Milky Way and extragalactic galaxies. The solar system is a part of the Milky Way. The earth belongs to the solar system. The earth goes around the sun, and the sun goes around the center of the galaxy.

7. Why should we protect wildlife?

Simply put, it is to maintain biodiversity. It is also a colorful symbol of our planet. Due to the excessive expansion of human beings and the development of science and technology, the speed of species extinction is accelerating now. It is conceivable that there are very few species, and it will be a terrible sight for humans to seize the earth in the end. In fact, by that time, the extinction of mankind is not far off. Therefore, we should protect wild animals and plants, let them multiply and grow on the earth, make our world better and make our future more sunny. Harmony is naturally a complete biological chain, and the lack of any link will have terrible consequences.

8. Talk about the relationship between the Earth, the solar system and the Milky Way.

The solar system is a part of the Milky Way, and the earth belongs to the solar system. The earth revolves around the sun, and the sun revolves around the center of the galaxy.