Question

When warm air rises in upward direction, then
(a) Air pressure decreases
(b) Air pressure increases

Answer 1

Answer:

             Air pressure decreases

Explanation:

The distance of atmosphere from the top to bottom (depth) seems higher at sea level and lower at higher altitudes. For better understanding, consider a given volume of gas with higher gas particles & collisions, you can find greater pressure.

The same way, higher the depth of atmosphere presses the air down from the top, hence air pressure decreases when warm air rises in upward direction.

Answer 2

Answer:

The correct answer :  (a).

Explanation:

• Air molecules are pulled down towards the earth due to the impact of gravity that acts on them and this creates a pressure of the air on the earth surface.
• Atmospheric pressure decreases as one goes from the sea level to higher altitude as most of the air molecules are drawn towards the earth surface, so the density of air molecules near the earth surface is far more than that away from it.
• Warm air has a lower density and is lighter, while cold air has higher density and so it is heavier.
• When warm air rises in the upward direction, a void space is created in the region where the air was initially present.
• Because of absence of air molecules in the void space, there is decrease or absence of air pressure in that region.
• But nothing on earth can be vacuum. Cold air from other regions come and occupies this vacant space. This causes wind to blow.