Why Is The Cup Attract By The Silicone Lid?

Because the total area produced by the contact between the lid and the mouth and the distance between the lid and the mouth are very small, the gravitational force between the lid and the mouth due to molecules is greater than the mass of the cup. In this way, when the pressure inside the cup is not greater than the atmospheric pressure, the cup lid will be sucked by the cup.

Most of the time, the residual liquid volatilizes in the cup, making the pressure in the cup stronger than atmospheric pressure. So the cup is attracted because of the gravitational force generated by the molecules between the cup lid and the cup mouth.

If the cup is filled with water and there is no air in the cup with the lid closed, the atmospheric pressure will tightly press the lid and body of the cup. The cup is sucked by the lid. If the lid is made of soft leather, then press the lid down, and then lift the lid, the air pressure inside the cup is less than atmospheric pressure, the cup and the back body will be pressed together, the cup is sucked by the lid.

The lid of the cup is in close contact with the cup. There is hot water and a certain amount of gas is left. When it is cooled, the gas pressure becomes smaller. If the cup is lighter and the pressure difference between the inside and outside is large, lift the lid to suck up the whole cup.