Is he Lianjia mining machinery a pyramid scheme

1. Static friction = static with respect to the contact surface. But notice that if the condition is smooth, there is no friction
the way is to see the movement trend of the object relative to the contact surface, where the object is going relative to the contact surface, and the direction of static friction is its opposite direction. If it's a wooden block on a rough slope, the static friction force must go up the slope, because without the static friction force, the wooden block will run down the slope. If you push a box and the box doesn't move, the static friction is the opposite direction of pushing the box. But notice that the motion is relative to the contact surface. Suppose you push the block to the right on a train running at a constant speed to the right, and the block does not move. The block is still subjected to static friction to the left
or do force analysis, analyze the force on the object - gravity, support, thrust or pull, and then judge where it will run but not run, then the friction is the opposite direction of the direction it wants to run.