题目　如图 1所示 ,将一个两端开口的玻璃管的下端挡住一个塑料片 ,竖直插入水中 1 0cm深处 ,往管中倒入酒精使酒精的液面与外面水面相平 .当玻璃管向上提高　　　cm时 ,塑料片恰好脱落 .( ρ酒 =0 8× 1 0 3kg/m3)该题一般的解法为 :当塑料片所受玻璃管内外液体压强相等时 ,? The problem is shown in Figure 1. A glass piece with two open ends is blocked by a plastic piece and inserted vertically into the water at a depth of 10 cm. Pour alcohol into the tube so that the liquid level of the alcohol is flush with the outside surface. When the tube is raised upwards by cm, the plastic piece just falls off. ( ρ = 0.8×10 3 kg/m 3 ) The general solution to this question is: When the pressure inside and outside the glass tube of the plastic sheet is equal to that of the glass tube,?