Scientific knowledge around us

1. Why does sorbet smoke?

Sorbet smokes because there is a lot of invisible water vapor in outside air. When it encounters a very cold sherbet, it turns into mist and surrounds sherbet when it is cold. It seems that sorbet "gassing" "The same.

2. Why do sunflowers always face sun?

Sunflower stems contain wonderful auxin. This auxin is very sensitive to light. When it meets light, it moves to backlight side, and at same time stimulates cells on backlight side to multiply rapidly, so backlight side grows faster than light side, which causes sunflower to produce phototropic bending.

3. Why do cicadas shed their skin?

The shell (exoskeleton) of cicada is hard and cannot expand as cicada grows. When cicada grows to a certain stage, cicada's exoskeleton restricts cicada's growth, and cicada removes original exoskeleton, this is cicada's swamp.

4. How do bees make honey?

The bees first spit sweet juice from plucked flowers into empty hive. At night, they suck sweet juice into their honey stomach to cook it, then spit it out and swallow it again. 100 to 240 times finally into sweet honey.

5. When a quartz clock hanging on wall runs out and stops moving, its second hand often stops at "9" position on dial. This is due to fact that second hand slows down gravitational moment most at position "9".

6. Sometimes when draining water from water supply from a nearby tap, bursts of noise periodically occur. This is due to resonance of water pipes when water is flushed from faucet.

7. When shooting in front of a TV screen, camera's flash and interior lighting should be turned off for clearer pictures. Because reflected light from flash and light on TV screen will interfere with transmitted light of TV screen.

8. Frozen meat thaws faster in water than in air at same temperature. A hot iron nail cools faster in water than in air of same temperature. A mug of boiling water cools faster when immersed in water than in air of same temperature. All these phenomena indicate that heat transfer properties of water are better than those of air.

9.When there is cold water in pot, water droplets adhering to outer surface of bottom of pot can burn dry for a long time on fire, and they will not boil until they dry. Or maintain thermal conductivity, temperature is about same until water in pan boils, water drops boil, and water drops evaporate on flame and gradually burn to dryness,

10. The mirror is out of shape, farther a person is from mirror, more out of shape. Since image in a mirror is formed by reflection from silver plated surface behind mirror, uneven silver plated surface or uneven glass thickness causes aliasing. For a non-standard mirror, farther a person is from mirror, greater deviation from normal position of reflected light on silver-plated surface, due to principle of light amplification, and greater deviation from normal position. -The shape of mirror will be.

11. There are several small holes on side of gas nozzle of a natural gas furnace that communicate with outside world, but natural gas will not be emitted through small holes on side, but only from nozzle. This is because gas flow rate in nozzle is large, according to principle of fluid mechanics, flow rate is high, pressure is low, and surface pressure of air flow is lower than atmospheric pressure outside. hole, so natural gas will not be thrown out through small hole on side of nozzle.

12. After inflating balloon, hold mouthpiece with your hand, then release it sharply, air flow in balloon is ejected, and balloon moves due to recoil. It can be seen that route of ball's movement is tortuous and changeable. There are two reasons for this: first, thickness and tension of inflated balloon is not uniform everywhere, so that when balloon is deflated, it is compressed unevenly and wobbles everywhere, so that direction of movement is constantly changing; secondly, shape of balloon is constantly changing during compression process. Therefore, speed of air on surface of balloon is constantly changing during movement. According to principle of fluid mechanics, flow rate is high and pressure is low, so air pressure on surface of balloon is also constantly changing, so balloon is swinging .

13. Why is there a whistling sound when wind blows

When a strong wind strikes a wire or a thin object such as a branch, it makes a "whistling" sound. air gap A vortex that makes air vibrate and make a sound The wind blows on a branch in same way as a whip At an acute angle or behind a gap, a vortex will also form when wind blows and create a "whistling" sound, and depending on strength of wind, pitch of sound will also different.

14. Why do you see lightning first and then hear thunder? (light waves travel faster than sound in air)