Saying that centrifugal force and centripetal force are a pair of opposite forces, why is there only a centrifuge and no centripetal machine? Is it not good to squeeze the material into the middle to increase the density?
The idea is good, but it is wrong.
First of all, what are the centripetal forces? The first thing that thinks about squeezing matter into the middle is the black hole. The black hole is also a kind of gravitation. What kind of centripetal force besides the gravitation caused by mass? If you use the gravitation to do the centripetal machine, it is not very reliable, and the quality required is too great.
Because in a non-inertial system that moves in a circular motion, the inertial force is always outward and there is no corresponding inward force. To maintain the object relatively stationary in the non-inertial system, other forces are needed to counteract this inertial force, such as the pulling force of the rope, the support of the outer wall, and the gravitation of a mass object. In fact, in all non-inertial systems, an inertial force can be fabricated according to the equivalent principle, the direction of which is opposite to the direction of acceleration of the non-inertial system (relative to the acceleration of the inertial system), and the magnitude is the acceleration multiplied by the mass of the object. This is done to facilitate the handling of the force balance in the non-inertial system, rather than who is actually applying such a force.
In addition, it should be noted that, in general, a pair of opposing forces refers to the force exerted between two objects, such as a slider on the floor, where there are opposite forces, respectively, the pressure of the slider on the floor and The support of the floor to the slider is not the same for both the floor and the slider. Then back to the topic, it can be said that the object has centrifugal force influence in the non-inertial system of the circular motion, but it cannot be said that the non-inertial system will be subjected to the centripetal force of the object, which should be noted.
