Excuse me, who was the first person who was refused entry in Moroccan casinos because of his outstanding gambling skills?

this frictionless movement of the inner wall of a circular track will never deviate from the track under the horizontal line of the center of the circle (even if the speed is reduced to zero, it will return to the original road). But after moving above the horizontal line of the center of the circle, there is no such return. At any point, g is decomposed in radial direction G1 and tangential direction G2. Below the O point, the required centripetal force is upward, and the rail pressure n (upward at this time) can be changed at will, and N-G1 serves as the centripetal force. Above the O point, the required centripetal force is downward. When the required G1 is insufficient to provide centripetal force (at this time, the speed of the object is high enough), the downward N will assist to provide additional centripetal force, and N+G1 will be used as centripetal force. But when G1 is larger than the required centripetal force (the speed of the object is smaller), the extra force will pull the object off the track. The highest point has the lowest speed and G1 is the largest, so this is the "worst" situation. As long as we can pass there, other points will not be off track. The critical condition is mg=mv at the highest point? /r, v is greater than or equal to this critical value, and can not be derailed, and vice versa.