1, light weight: According to the principle of lever balance, if the power arm is a fraction of the resistance arm, then the power is several times the resistance. If the weight of the arm is very large, it is entirely possible to "dial one or two kilograms."
2. A broken mirror cannot be reunited: when the distance between molecules is large (more than several hundred angstroms), the attraction between molecules is very small, almost zero, so it is difficult to reunite a broken mirror.
What you can't catch is the flower in the water that you can't catch in the mirror: the flat mirror forms a virtual image.
4, people are United, Taishan moves: if the component directions are the same, the resultant force is equal to the sum of the components.
5, hemp rope to lift tofu-can't lift it: when the pressure is constant, if the stress area is small, the pressure will be great.
6. "True gold is not afraid of fire, and truth is not afraid of argument." Judging from the melting point of gold, although it is not the highest, it is 1068℃, while the temperature of general flame is about 800℃. Because the temperature of the flame is lower than the melting point of gold, gold cannot be melted.
7. The moon is dizzy and windy, and the foundation is wet and rainy: when the wind comes, the temperature at high altitude drops rapidly and the water vapor condenses into small drops. These small water droplets are equivalent to many prisms, and the moonlight is scattered through these "prisms" to form a colorful halo, so it is said that "the halo is windy." The basic nourishment is the ground against the tide. Before the rainstorm, the air humidity is high, the ground temperature is low, and the water vapor near the ground condenses into small water droplets. In addition, the salt contained in the ground is easy to absorb wet water vapor, so the ground is against the tide, which indicates shanghai dawn.
8, a long whistle, the sound of the mountain is like a valley: people whistle in the mountains, and the sound can form a loud echo after repeated reflection, which lasts for a long time. As if the mountains were shouting and the valleys were echoing.
9. But you can't see people when you listen to the sound: when the size of the obstacle is smaller than the wavelength, obvious diffraction will occur during the wave propagation. Generally, the height of the fence is several meters, and the wavelength of sound wave is larger than the height of the fence, so you can enclose the high wall for people outside the wall to hear; The wavelength of light wave is shorter (about 10-6 meters), which is much smaller than the size of a high wall, so the light emitted by people cannot be diffracted outside the wall, and people outside the wall can't see people inside the wall.
10, boiling water doesn't ring, water doesn't ring: Before the water boils, bubbles in the water rise and vibrate up and down due to convection, and most bubbles burst under the pressure of water, and their cracking and vibrating sounds ring with the container, so the sound is very loud. After water boils, it is isothermal up and down, and the bubble volume increases. Under the action of buoyancy, it will burst as soon as it reaches the water surface, so the noise is relatively small.
1 1, Pig Bajie looks in the mirror-inside and outside are not people: according to the imaging law of plane mirror, the images formed by plane mirror are equal in size and the objects are symmetrical, so what Pig Bajie sees is "exactly the same" as himself, or the image of a pig, and naturally "inside and outside are not people".
12, fire and water incompatibility: when a substance burns, it must reach the ignition point. Because of the large specific heat of water, water can absorb a lot of heat when it comes into contact with fire, which reduces the temperature of the ignited object; At the same time, the vaporized water vapor surrounds the burning object, making it impossible for the object to contact with air. Without air, combustion cannot be carried out.