Re: Why do doors slam when there is a window open?

Hello, Alyssa:

Oh, Boy!  A Locked Room Mystery!

What I suspect is happening is that the closing door is slightly 
compressing the air in the room.  This higher-pressure air resists the 
door’s movement, causing it to strike the frame less violently.  When a 
window is open, the air in the room is not compressed as much, there is 
less pressure on the door, so that the same effort to close it results in 
the door hitting the jamb harder with more of a “Slam!”   

I suggest you test this by using some smoke, like from an incense stick.  
Hold it next to the door.  Push the door closed with the window closed 
and open; try to apply the same effort.  If I’m right, there should be a 
puff of air out the door when the window is closed, and not when the 
window is open.  Hold the smoke next to the window, too, when it’s open—
there should be a puff out at the instant the door is closed.  (there 
isn’t much point in holding the smoke next to the closed window, is 
there?)

This principle is used in a lot of machinery that translates back and 
forth.  At the end of a stroke, a loose-fitting piston plunges into a 
cylinder.  The resulting soft spike in pressure slows down the moving 
part just before it hits the solid stop, reducing the wear-and-tear on 
the equipment.

Enjoy the Olympics!

C.H. “Chas” Hague