Why does the "air" close or open doors? Assume we have an empty room with two doors on the opposite sides of it. If we open one of the doors, the door on the opposite side automatically closes "harder", and if we close one of the doors the other door opens. Why does this happen?
 A: If a door opens outward, pulling it open creates a slight lowering of air pressure inside the room just for a moment. If the door on the other side opens inward, then the slightly greater air pressure on the outside of that door will push it open. 
The reverse is true when you close that door by pushing it inwards. The air pressure in the room rises slightly because the door is pushing air into the room, and if the other door opens outward, then that slight increase in air pressure inside the room will push that door open. If it opens inward and is open, it will get pushed shut by the air pressure when you shut the other door. 
A: Assalamu Alaikum.
This is air pressure So, basically air pressure is a force extracted into a surface by the weight of the air. In a specific room if you open your window you will realised that door is closing by it self. But it is because of air pressure. It pushes the door slightly. Mostly depend on the air pressure present at that door. If the door is closed when you be realising that the door is automatically opening by its self. This is of air drag. Basically air drag actually pulls  down everything. From a slightly open position.
Jazak Allahu Khairan.
