Tiangong Classroom's little knowledge is as follows:
1. Space turn experiment In the "Tiangong Classroom", astronaut Ye Guangfu performed "space turn". The first time he tried to turn around normally, he failed - every time he twisted his upper body, his lower body would involuntarily twist in the other direction. Why?
The reason why we can move forward and turn easily on the earth is because the ground has friction. And astronauts who "float" in the air in a weightless state do not have the help of friction, so it naturally becomes very difficult to turn their bodies. Because the astronaut's angular momentum is conserved, when the upper body turns to the left, the lower body will turn to the right.
In the second attempt, the astronaut achieved body rotation by rotating his arms. This can also be explained by conservation of angular momentum. ?
2. The disappeared buoyancy experiment space station. Astronaut Wang Yaping put a table tennis ball into the water and found that the table tennis ball could not float.
This is because the essence of buoyancy is the pressure difference between the upper and lower surfaces of an object. The prerequisite for generating buoyancy is the existence of gravity. Buoyancy will fail in a weightless environment, so the table tennis ball in space can sink into the water, which is impossible on earth.
3. Water film tension experiment Water on the earth will flow from high to low due to gravity. But in a weightless environment, the astronauts transferred the water to a special iron ring. Because of the surface tension of the water, a crystal clear water film was formed that would not break.