Why do doors slam when a window is open in the same room?
In: Physics
When the window is closed, the air in the room has to compress or escape from the tiny cracks around.
The air then slows the door down.
When the window is open, all the air goes out the window, so there is nothing to slow the door down, so it slams.
When you open windows and doors you let air blow through the house. This can create differences of pressure in your house. If a room with higher pressure has a door, that higher pressure can force that door shut.
For the same reason that airplanes fly.
Ok, so when you open a window and door, air goes streaming in the room and out the open doorway. That’s the easy part. Now if you have your door open more than 90 degrees, how can it slam closed? Shouldn’t the moving air just push it out of the way? Well here’s the thing: moving air has less pressure than still air. When that breeze hits your door on the way out of the room, it creates a pressure differential. The moving air on the doorway side has less pressure than the still air on the wall side, so it sucks the door towards the doorway. Then, as it passes the 90 degree mark, suddenly the door is in the pathway of the breeze. The air wants to keep moving, so it pushes along whatever is in its way. As the door closes more and more, the pressure differential between the the rooms increases, forcing the door to move faster. By the time it shuts, it’s moving so fast that it slams. To prevent it, you need enough force pushing back against the door to overcome the air pressure differential. Usually people accomplish this with something heavy, like a brick. The suction force of the air is no match for the frictional forces of the brick, and your door stays put.
Latest Answers