In the midst of all the AP's, Physics Final Exams, homework, and attempting to find time to sleep, I noticed a spontaneous bit of Physics the other day. In my windy Manoa home, where the bamboo bends nearly horizontally under some winds, I noticed that our closed front door (pictured above) was banging back and forth as far as the deadbolt lock (upper circle on the left) would let it. I then noticed the strong winds outside and realized.....Phyiscs!!!!!!!!!!! I decided that there were two possible explaination for this: one, the wind was pushing on the door, applying a force equal to the sum of (the masses of the air molecules times their acceleration), causing the door to accelerate inward until it hit the deadbolt; then when the gust of wind stopped, the door would return to its inital position from the force of the internal pressure in the house (F=PA). Scenario number two: the wind was not blowing into the door, but across it; therefore, by Bernoulli's Principle, the external pressure would decrease as the air velocity increased, pushing the door outward with the force of the net internal pressure, then returning as the wind speed decreased again. Or, perhaps, it was some of both, I'm not sure. But even the wind is a process of Physics; as a region of air increases in temperature, it expands in volume, decreases in pressure, and decreases in density, rising, making way for colder air to fill the void and creating wind. The opposite is probably true as well, and that's probably what happens in the valley at night. It sure makes for an interesting knocking noise while I'm supposed to be eating dinner or doing homework. :-)