Place a glass and fill it up with the water up to the brim. Keep the set up such that there is no air bubble inside it. Place a thick, stiff piece of the cardboard and put it over the glass. Take your hand over the card and suddenly turn the glass upside down. Now remove your hand slowly. What will be the result of this experiment?
A. Air occupies space.
B. air exerts pressure.
C. air has weight.
D. all of these.
When we will remove our hand, then we will find the card will be kept in place and the water will not flow out. This is because of the air that is exerting a pressure on the card from below to make the card kept in place. Therefore, the pressure exerted by the air upwards will be more than the pressure exerted by the water downwards. Therefore the air is exerting the pressure in order to keep the cardboard in place and to make the water not flowing out.