Source: CCTV News Client
This afternoon (September 21st), the fourth lesson of "Tiangong Classroom" officially started. Shenzhou 16 astronauts Jing Haipeng, Zhu Yangzhu and Gui Haichao taught space science popularization to young people across the country.
In a microgravity environment, what happens when the centroid collision of steel balls of different masses occurs? In high school physics, we learn the law of conservation of momentum. On the ground, teachers often need to use auxiliary tools such as Newtonian pendulums in order to demonstrate the law of conservation of momentum, and on the space station, the law of conservation of momentum can be demonstrated in a simpler and more direct way. Let's take a look at ↓↓↓
Astronaut Zhu Yangzhu: Behind our hatch hides a secret teaching aid, this is a one-meter square standard grid cloth, students these small squares are 10 centimeters× 10 centimeters in size, now I take out a solid steel ball in my hand, the mass is 500 grams, the diameter is 49.5 mm, now I put it in the center of the front of the mesh cloth.
Astronaut Gui Haichao: Students, I have an identical steel ball in my hand, and then I am ready to throw the ball in my hand to collide with the stationary ball, let's verify the law of conservation of momentum in the space station.
How do small steel balls of the same mass move when they collide?
Astronaut Gui Haichao: Students see, after the collision of two balls, momentum exchange occurs, and students can calculate whether the system composed of two balls before and after the collision meets the conservation of momentum according to the picture we demonstrated just now. Just now, we demonstrated the collision of a ball of the same mass, I also have a small steel ball with a mass of 100 grams, and then I am going to use the small ball to touch the big ball, let's see how the phenomenon will be different.
How do small steel balls of different masses move when they collide?
Astronaut Gui Haichao: Students, after the small ball touched the big ball, it turned around and returned to Mr. Zhu's side, and the big ball continued to move in the direction of the initial movement of the small ball.
Astronaut Gui Haichao: Let's do a big bump situation, after the collision, the small ball and the big ball continue to move in the direction of the initial movement of the big ball.
Astronaut Zhu Yangzhu: I will demonstrate it to the students again.
Astronaut Gui Haichao: In the same situation, students can find through calculation that the collisions we demonstrated just now meet the conservation of momentum, whether they are close to the positive collision or the oblique collision. But please note that the physicists who proposed the law of conservation of momentum back then did not have the ideal experimental conditions we have today, and they relied on meticulous logic and simple experimental equipment to promote the continuous development of physics, so that we can demonstrate such a classical physical law for you in the space station today.
Astronaut Zhu Yangzhu: Yes, here, we want to pay tribute to those masters of physics.