Scientific phenomena around us

1 1. Even if there is no wind, the path of paper dropping is tortuous. This is because each part of the paper has different convexity and concavity and shape, so in the process of falling, the air speed on its surface is different. According to the principle of fluid mechanics, there is uneven air force everywhere on the paper, which changes with the movement of the paper, so the paper keeps rolling and falling zigzag. 12, can we read the scarlet letter written on a piece of white paper through a piece of red glass? Many people have their own opinions on this issue. Some people think so, others think not. Moreover, people who think they can see clearly are based on the scarlet letter on white paper because red is darker than white. If you cover this paper with a piece of red glass, it is equivalent to adding a layer of red to the white paper and the scarlet letter, so that although the paper will turn red, the scarlet letter will also be added with a layer of red, which means that red is deeper or darker than paper, so the words can still be read clearly. I think the reason why I can't see it is simple: because the red color of glass is the same as the red color of paper, the white paper that passes through the glass will turn into the red color of glass, and the red words will turn into the red color of glass when they pass through the glass (in fact, it has not changed, because the color of glass and words is the same). In this way, the white paper and the scarlet letter turn into the red color of the glass after passing through the glass, and naturally it is impossible to recognize the words. After experiments and research, it is found that it is actually impossible to see clearly. In other words, the scarlet letter will be aggravated by the overlapping of red glasses. It's like you have a red gouache painting on paper, and then you draw the same red in the same place later, only adding a three-dimensional sense to this color (which belongs to the art category and has nothing to do with physics), but the color has not changed. 13. See if the egg is broken. When we pinch an egg, the lever force of the hand is evenly distributed in all parts of the egg, which is not enough to crush it, because the shape is the most stable shape. People use this principle to build arch bridges. Although it looks thin, the traffic ran over it and it still stands still. Zhao Zhouqiao, for example, has stood there for thousands of years, crossed the other side, bent down and stared at the rolling river flowing far away. People also use this principle to build arches and design cars, planes and helmets.

Eggs can't be crushed? But have you ever tried to squeeze two eggs with one hand? You can crush them easily. Why? In fact, when we pinch two eggs with one hand, the force of the handle of the hand is concentrated on the contact point of the two eggs. Because the contact point is the stress point and the area is very small, the egg is broken at once. Don't say two eggs, even if you pinch two walnuts in one hand, you can crush them. This is the same principle. 12, using things around you to carry out physical experiments, which is an innovation in itself. Please design several physical experiments (force, heat, sound, light and electricity) with common cans (full or empty cans) as the main experimental equipment and some other equipment.

The main equipment added, the physical problems explained or studied by the main experimental process or method (whether written expression or drawing explanation).

Punch holes 1 nails and water nails at different heights of empty tanks, and compare the relationship among the spraying distance, internal pressure and depth of liquid after water filling.

Can two empty cans of cotton thread and nail be connected with cotton thread to make a "earth phone" solid to transmit sound?

Put the cans on the inclined plane of the board and slide down and roll down from the same position respectively. Compare the movement speed under two conditions, and compare the sliding friction and rolling friction under the same conditions.

4 Wire, clamp, switch, light bulb and power supply Connect the power supply, switch, light bulb and empty tank into a series circuit with the clamp, and close the switch to see if the light bulb glows. Is the material of cans a conductor or an insulator?

5 Black paper, white paper, water and thermometer are packed with white paper and black paper respectively, and exposed to the sun for the same time to see if the temperature of white objects and black objects is the same under the same conditions.

6 thick sponge block Let the cans filled with cans be placed horizontally and vertically on the thick sponge block, and observe the depression of the sponge and the relationship between the pressure and the stress area.

13, as shown in the figure, is an electric kettle commonly used in family life. Please ask two questions about the structure or use of physics knowledge and give a brief answer.

For example, question: What containers are the spout and body made of?

A: They formed a communicator.

Question 1: What does the pattern on the handle do?

Answer 1: By increasing the roughness of the contact surface, beneficial friction is increased.

Question 2: Why do you want to make the handle wider?

Answer 2: Reduce the opponent's pressure by increasing the stress area.

Question 3: Why do you use a three-pin plug for the power connection cable?

Answer 3: The electric kettle shell is grounded to prevent electric leakage and electric shock.

Question 4: How is energy converted when water is heated?

Answer 4: Electric energy is converted into internal energy.

Question 5: How is the "white gas" coming out of the hukou formed?

Answer 5: It is formed by the liquefaction of water vapor sprayed from the spout. Question 1:

14, Xiao Ming made an expository article about "crossing the bridge rice noodles" in Yunnan in Chinese class, which is now extracted as follows:

"Crossing the bridge rice noodles" is a famous traditional snack in Yunnan. Its cooking method is to put the freshly cooked chicken soup into a large bowl, then scoop a spoonful of hot oil into the bowl, and soon form a thick oil film on the surface of the soup. At this time, the raw meat slices prepared in advance are put into the bowl in turn. Surprisingly, the soup that doesn't even steam on the surface actually cooked the raw meat slices.

Please use your physical knowledge to make a reasonable and correct explanation of the physical phenomena described in the above article.

Answer: (1) "A thick oil film is quickly formed on the surface of the soup", because the density of oil is less than that of the soup, and the oil floats on the surface of the soup to form an oil film.

⑵ "Soup whose surface doesn't even steam" is because the oil film separates the contact surface between the soup and the air, which effectively prevents the soup from evaporating, so it doesn't steam. ⑵ "The soup that doesn't even steam actually burns the raw meat slices". The temperature of the soup is actually very high, which causes heat transfer, and the meat slices absorb heat, which increases the internal energy.

15. Pliers with rubber handle for electrician. A lot of physical knowledge we have learned has been applied to its design and use. Please point out two places where this tool applies physical knowledge in design, structure or use, and write down the physical knowledge on which it is based.

The physical knowledge on which the application of physical knowledge is based.

1 The cutting area is small, which can increase the pressure.

There are concave and convex patterns on the surface of plastic handle, which can increase friction.

3 plastic handle plastic handle is insulating plastic, which can be insulated.

The whole clamp is a labor-saving lever, which can save labor.

The jaw is rough and has many grooves, which can increase the pressure and the buoyancy of the friction boat.

Bicycle letter pole

Brake friction

When the elevator rises, the pressure on the floor is even greater-overweight.

The elevator is lighter when it descends-weightlessness

Cars drift when turning-centrifugal force.

Tape playback-electromagnetic induction

When the police car is away from you, the flute becomes slow-Doppler effect.

Long jump-action and reaction

Induction cooker-eddy current