Chapter 20, Problem 67A

Place a card over the open top of a glass filled to the brim with water, and invert it. What happens? Why? Try turning the glass sideways as shown below.

To determine

To explain: The effect on a glass of water along with reason.

Answer to Problem 67A

The water will not come out of glass.

Explanation of Solution

Introduction:

Atmospheric pressure: It is the force exert by atmospheric weight. Its unit is pascal.

When a card is placed at the top of a glass filled with water, at that time at the top of the glass a small pocket of air is created and more air molecules cannot get into that space, hence a small pocket of low pressure is created. When this glass of water is inverted that time air molecules which are present in large amount outside the glass exert pressure at the bottom of the card, due to which higher pressure area is created in comparison to lower pressure area inside the glass. The force produced from atmospheric pressure holds card up and due to low pressure zone in the glass card will not get pushed down hence water will not come out of glass.

Conclusion: The water will not come out of glass.