Question

Задача: Возьмите стакан (лучше тонкостенный) и поместите его в горячую воду. Вытащите его из воды и опрокиньте вверх дном на клеенку стола, слегка придавив. Через несколько минут попробуйте снять стакан с клеенки. Почему это трудно сделать? Ответ: Сначала стакан был нагрет, и давление в нем было атмосферным. После охлаждения давление уменьшилось и стало меньше атмосферного. Поэтому оторвать стакан от стола трудно. Вопрос: Почему при понижении давления внутри стакана его сложнее оторвать? Как это объяснить?

Answer 1

Все обь9сн9етьс9 тем что при большеи температуре молекулы увеличиваетьс9 (они более быстро двигаютьс9 происходит расширение), соотвественно оно и уменьш9етьс9 при этом движение молекул замедл9етьс9 соотвественно и места им меньше им надо, поэтому между стаканом и скатертью создаетьс9 вакуум 

Answer 2

Why is it difficult to lift the glass after it has been cooled down?

When a glass is placed in hot water and then removed and turned upside down on a tablecloth, it becomes difficult to lift the glass off the tablecloth. This is because of the change in pressure inside the glass.

Initially, when the glass is in the hot water, the air inside the glass is at atmospheric pressure. However, when the glass is removed from the hot water and cooled down, the air inside the glass cools down as well. As the air cools, it contracts and its volume decreases. This decrease in volume leads to a decrease in the pressure inside the glass.

The pressure outside the glass, which is at atmospheric pressure, becomes greater than the pressure inside the glass. This creates a pressure difference between the inside and outside of the glass, with the outside pressure being higher. This pressure difference causes the glass to be pressed against the tablecloth, creating a vacuum seal.

The vacuum seal makes it difficult to lift the glass off the tablecloth because the pressure difference holds the glass firmly in place. The higher atmospheric pressure outside the glass pushes the glass against the tablecloth, creating a strong adhesive force.

To overcome this adhesive force and lift the glass off the tablecloth, you would need to break the vacuum seal by introducing air between the glass and the tablecloth. This can be done by gently tilting or sliding the glass to allow air to enter and equalize the pressure inside and outside the glass. Once the pressure is equalized, the glass can be easily lifted off the tablecloth.

In summary, the difficulty in lifting the glass off the tablecloth after it has been cooled down is due to