Question

Take a glass full of water (fig. A) put a piece of thick card on it. Now turn the glass upside down as shown in fig. B What will happen?

• A. The card will not fall
• B. The card will fall down
• C. Water will leak through the sides
• D. None of the above

Answer 1

The correct option is A The card will not fall

Firstly the reason for the phenomenon is the atmospheric pressure. The weight of water and card is countered by the force exerted on card upward due to the presence of air at its bottom.

Another reason is adhesion of water molecules to cardboard and glass.It occurs because water molecules, having the positive and negative ends, are also attracted to other materials. In the experiment, the water molecules are attracted to the paper, adhering to it, while continuing to keep the surface tension with the other water molecules. This keeps the note card in place.