Why does my door shut faster when the window is open? I've noticed that if I shut my door when the window is open in a room, the door will tend to shut faster. If I shut the door when the window is closed with a normal force it will not fully close as if the air is cushioning it. I think when the window is open the door doesn't stop or slow down at all, it just slams.
I was wondering if this was to do with the pressure of the room or something. My hypothesis was that there is more room for the air to escape or there is some sort of convection? Just to note it is definitely not wind because I checked.
Here is a graphical simulation of the phenomenon: 
Can somebody explain what is going on?
 A: As the door nears the door frame there reaches a point where the door, for a moment, effectively seals off the air in the room from the air outside the room.  This only happens for a moment, since most doors aren't 100% air proof. When this happens, as the door continues to close it decompresses the air inside the room, because the volume of the room increases as the door continues to close but the amount of air inside the room doesn't change because the room is briefly sealed off from outside the room.  Thus there is an air pressure difference across the door, with the greater pressure coming from outside the room.  This greater pressure slows the door down right before it closes.
On the other hand, with a window open air is let into the room and so even though the volume of the room increases as the door closes the air pressure from outside the window pushes air into the room to keep the air pressure inside the room about the same as outside.  No pressure air pressure difference is found across the door and thus it does not slow down.
It is also possible that a fan or something inside the building could be creating a lower air pressure inside the building and thus there is a small air flow from the window into the building, which would push the door to close faster one the above-described brief sealing of the room happens, thus increasing the volume of the "slam!".
A: When the window is closed, there is no place for the air in the room to go once it's passed through the doorframe.  So little air will pass the doorframe and won't act on the door.  Picture an electric circuit with a wire dangling, leading to nowhere.
Opening the door reconnects the wire, so to speak, and allows air flow.  The flow may not be very noticeable, but the door has a large surface area and experiences a relatively large force from a relatively small PSI once it starts to get in the way of the flow.
A: According to me, if you try to close the door with the window open it will get closed as usually. Here the air from outside your room enter your room through the window. If you try to close the door with your window closed no air will enter your room from outside, hence the air that was in your room expand(negligible)(rare) or a low pressure will be created (normally). This low pressure tends to pull your door back . But it'll not be pulled completely because as soon as the low pressure pulls the door, the air from outside enter your room through your door and the low pressure will be stabilised. I think you've noticed that this will happen only if you close the door suddenly and you might not have noticed this phenomenon if you close the door slowly.
Another phenomenon that I've observed is, when you open you open your door suddenly with your  window closed (BUT NOT LOCKED) your window will be opened suddenly due to high pressure created inside your room.
Forgive me if I've spoken wrongly, since I'm still a learner. And please correct me if I'm wrong.
A: It depends on the situation on both sides of the door.
But the answer is related to pressure differences - effectively the air is blowing the door shut just like when you have a draft - but it is not strong enough to slam the door by itself.
Sometimes you'll find you barely tap the door and it slams shut - this is due to the difference between kinetic and static friction. Your tap provided just enough energy to overcome the static friction and the air does the rest.
You will need careful tests to be able to tell, in detail, what exactly is going on. Like I say, vary the situation on both sides of the door.
A: I think this happens because when windows are open then there is free airflow in the room and doesn't affect the shutting of the door but when the windows are closed then there is obstruction in airflow. The pressure of air inside the room become less than the pressure of air outside the room and hence obstruct the shutting of the door in the room having all windows closed.
A: when you open a door to an apartment and there is a window open it will surely slam shut any door in between and if there is no door in between it will slam the door you have just opened unless it is a sliding door I have experienced this many times in the Algarve as there is nearly always a breeze over there think about a famous case there a few years ago and I am sure you will conclude as I did that the window could not have been open.
