This reason is a bit broad. Shutdown is a possibility. It may be that the variable pitch system makes the angle of the blade reach 90 degrees, which refers to the minimum windward surface of the blade, so that the blade cannot fully face the wind, thus causing the wind speed It still cannot rotate after reaching the rated wind speed; it is also possible that the yaw system causes the blades to not face the wind; and the wind speed in winter is the same as the wind speed in summer, but the blades can rotate in winter, but they may not rotate in summer, because In winter, the temperature is low and the air density is high. In summer, the temperature is high and the air density is low. This is what we Northeasterners often say: the wind in winter is strong, but the wind in summer is not strong.
1. Activity goals:
1. On the basis of learning to make windmills with square paper, boldly try to make windmills with a variety of regular graphic papers.
2. Be able to perceive the relationship between the structure of the windmill and its rotation, and understand the principle of windmill rotation.
2. Activity preparation:
1. Several finished paper pinwheels of various shapes.
2. Several colored papers with various regular graphic shapes.
3. Auxiliary materials: straws, plasticine, scissors, glue, pins.
4. Arrange the venue: Windmill Exhibition.
3. Activity process:
1. Provide various finished windmills, and the teacher plays with them to arouse children's interest in making.
2. Observe the windmill, analyze the production materials and methods, and guide the children to make it.
Children, let’s take a look at what is on the windmill and what we call them (windmill blades, windmill poles, windmill axles) and talk about it together (children’s answer).
1. Taking the windmill made of square paper as an example, teachers and children discuss and analyze the methods of making windmills.
2 children try to make.
3. Try to use other shapes of paper to make windmills, and explore what shape of paper is more suitable for making windmills.
Assign a task: Let the children be the little doctors of the windmill. Please use your brain: Why does the windmill spin? And some children’s windmills can’t rotate? What shape of paper windmill will rotate and why? Then quietly tell the teacher the secret you discovered. Are you ready, children? Bring all kinds of windmills we made and let’s go!
3. Play with windmills outdoors, and teachers will provide guidance.
4. Teachers and children share their findings together.
Aren’t the children having fun? (Children’s answers) The teacher asked a few children who were not having fun to talk about the problems they encountered.
Xiao You: "Teacher, my windmill won't turn even if I run around..." Guoguo: "Teacher, my windmill always collapses..." Pengpeng : "Teacher, my windmill will spin only if I move it, but it won't spin if I don't move it..."." Teacher: "Then have you tried running or spinning in circles to help it turn? Peng: "Yes, it just doesn't spin."
Teacher summary: If the windmill wants to spin, first it must be made of paper with symmetrical shapes, so that the two sides of the windmill can be balanced, so that the wind When it blows, the force of the wind on both sides is the same, and it will start to rotate. Then if your windmill is symmetrical and you haven't started to rotate yet, it is possible that when making the windmill, the children cut the part where the wind blades were cut. It's too far, so you should make more space around the center point. Also, when fixing the windmill, the child's pins are too far in place. You should move the pins further out to make the wind blades appear bulging and looser.