springtime physics
Entry posted by jfrachioni
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yesterday i opened the window in my room because it was particularly warm outside, and throughout the day as i entered and left my room, i would accidently slam my door, even though i was accelerating it to the same speed to close it as i usually do. as i got used to my now much easier to close door, i thought about possible explainations for this annoying phenomenon. i hypothesized that the culprit was my open window. i figured that when the window was closed, the shutting of my door was harder because while shutting, i was doing work not only on the door, but also on the gasses inside my room because the door acted like a plunger, increasing the volume of my room faster than air could enter and decreasing the pressure inside. with my window open, gas can come in both through the window and through the crack under the door, increasing the speed at which air could enter, therefore decreasing the difference between the rate of incoming air and the rate of increasing volume. with this difference smaller, the door does less work on the air inside because it doesnt need to decrease the pressure to close. with the window closed, i was used to giving more speed to the door to close it, but now that the window is open and less of the energy i give the door is used to change pressure, the speed i usually use is too much, and the door slams.
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