To be a scientific problem in life, a scientific problem in life

Science is the bridge for mankind to move towards a new era, and it is with science that there will be today's household equipment. It is precisely because of science that reform and opening up will succeed and people will be able to live and work in peace and contentment. It is with science that laughter fills everywhere.

In the past, I always thought that studying science was useless. Only learn the language. There will be development in the future.

Until one day a small experiment changed my opinion. That was when I was in third grade, and it was Sunday. I felt very bored because I had finished my homework.

So I went to play with Sha Li, who was in the fourth grade, and it just so happened that he was also idle. So he proposed to play table tennis. As soon as I heard this, I immediately clapped my hands and shouted, 'Yes, yes!'"

So he gave me a ping-pong board. Then he took me to the ping-pong table in his backyard. He said to me

Ready, I'm serving. "With that, I just heard a 'bang', and the ball flew towards me like a rocket. I was in a hurry, but fortunately I was at a loss and hit it back.

However, after all, I have just learned table tennis. It wasn't long before the ball hit the ground and I was about to pick it up. Slippery underfoot.

The ping-pong ball was flattened on the spot. I slowly picked up the ping-pong ball and said apologetically to Shali, "I'm sorry for flattening your ball."

Shali looked at the ball for a while, then suddenly brought a basin of hot water and told me to put the flat ping pong ball in it. A miracle happened! The flattened ping pong ball slowly became round in the hot water.

I was supposed to be amazed. At this time, Shali said with a smile"This is called 'thermal expansion and cold contraction', and the ping pong ball expands when heated.

A flattened ping pong ball will be rounded. This phenomenon will be learned in your fourth grade. "When I heard this, I couldn't help but feel stupid when I thought about my previous views on science class, and that was when I was rational about learning science class.

Can you cook tofu and spinach together?

Categories: Education, Science, >> Learning Aid.

Problem description: 1. How can I measure the sweetness of watermelon without cutting it?

2. How to use the simplest way to identify whether the fresh vegetables you buy have used pesticides?

Analysis: 1: First of all, we know that the ripe watermelon will be sweet, pat the watermelon and listen to the sound, the sound is green enough for the ripe melon, if it is muffled, it is too ripe watermelon (rotten).

Second, look at the melon vines, the ones that are green enough are fresh melons. Third, look at the texture of the melon, if the texture is clear and uniform, it is a ripe melon.

2: Look at the vegetables for any traces of insect bites, we know that insects will not eat pesticide vegetables. Second, look at the color, too bright, unnatural are all pesticides, with occasional exceptions.

1. The quartz clock hanging on the wall wall often stops at the position of "9" on the dial when the battery is exhausted and stops moving. This is due to the fact that the second hand is most hindered by the gravitational moment at the "9" position;

2. Sometimes when the water pipe discharges water from the adjacent faucet, there is an occasional burst of noise. This is due to the resonance of the water pipes caused by the water flushing out of the faucet;

3. When taking pictures of the TV screen, the camera flash and indoor lighting should be turned off, so that the ** picture is clearer. Because the reflected light from the flash and lighting on the TV screen will interfere with the transmitted light of the TV picture;

4. The tensile force of the suspension point is smaller than that when the ceiling fan rotates normally than when it is not rotated, the greater the speed, the more the tensile force decreases. This is because the air has an upward reaction force on the ceiling fan blades when the ceiling fan rotates, and the larger the speed cavity Zen, the greater the reaction force;

5. Thin pieces of paper falling from a height, even if there is no wind, the route of the paper falling is tortuous and changeable. This is due to the different convex and concave parts of the paper, so the airflow velocity is different at various points on its surface during the falling process. The flow rate is large and the pressure is small, which causes the uneven air force everywhere on the paper, and changes with the change of the movement of the paper, so the paper is constantly tumbling and falling.

I discovered the scientific problems around me and found the relevant theoretical knowledge.

1. Why do some trees lose their leaves in winter, leaving only branches?

Because the leaves of deciduous tree species are not able to carry out normal photosynthesis due to the low temperature, the leaves should be shed in autumn to avoid consuming too many nutrients. The other is that the leaves can live for two to many years, mostly in spring and summer, after the new leaves germinate, the old leaves fall off in the last plant, as far as the whole tree is concerned, it is evergreen all year round, called evergreen plants, such as pines and cypresses.

Leaf shedding reduces water loss, and late autumn or dry season leaf shedding can be seen as an adaptation of plants to avoid excessive transpiration. The leaves of the pine tree are needle-like, also known as pine needles, which reduce the transpiration area, and the epidermis is thick and the cuticle is developed, and these structures can reduce transpiration and adapt to arid environments, so they are evergreen all year round.

2. Why does a rainbow appear when oil is poured into water?

Because the density of oil is smaller than that of water, it floats on the surface of the water, forming a film of oil, and the refraction of light by this film causes a colorful rainbow halo, similar to the photolysis experiments caused by refracting light with a prism.

3. Why are the days short and the nights long in winter? And the opposite is true in summer?

Because in summer, the sun mainly shines on the northern hemisphere, and the area of the sun in the northern hemisphere is large, and the days are long, and in winter, the sun mainly shines on the southern hemisphere, and the southern hemisphere shines on the area less, and the days are short.

4. Why does it snow in winter?

Because the temperature is quite low in winter, the temperature on the ground is also below freezing, so the temperature of Paga touching the clouds in the sky is even lower. The water vapor in the clouds can directly condense into small Xiaoice crystals and small snowflakes, and when these snowflakes increase to a considerable extent, the air flow will not be able to drag it, and it will fall from the clouds to the ground, which is snow.

5. Why can't I drink expired water?

Because the water is stored for a long time, it will produce nitrite by itself, although the content is relatively low, but it will cause great harm to the human body for a long time, which is why it is not recommended to drink overnight water. Because the mineral water is relatively clean and well sealed, it deteriorates slowly, but it does not deteriorate and will cause greater harm, so it is better not to drink expired mineral water.

1. Boiled eggs are overcooled in cold water, using the principle of thermal expansion and cold contraction, and the chicken hole shrinks so that there is a gap between the egg skin and the cold water, and the cold water can enter the gap, so that the egg is easy to peel.

2. Wrenches, pliers, and scissors all use the lever principle, which can save a lot of effort.

3. Fish have the ability to tremble and come and go freely in the water, so people imitate the shape of fish to build ships, and imitate fins with wooden oars. Legend has it that as early as the Yu period, the ancient working people of our country observed the fish swimming and turning with the swing of their tails in the water, and they set up wooden oars on the stern of the boat. Through repeated observation, imitation and practice, it was gradually changed to oars, rudders, and oars, which increased the power of the boat and mastered the means of making the ship turn.

In this way, people can make boats sail freely, even in rough rivers.