car shock

As I was getting out of the car today, I got shocked again. The feeling is just like the zap from Vegas when you accidentally bump into someone. When two objects touch, if one has a charge and the other is neutral, electrons will move to whichever object is more positive. This is because objects want to stay neutral. In the situation with my car, I'm pretty sure that I'm neutral and the car door must have a negative charge. I'm probably neutral because I don't remember doing anything that would cause me to gain or lose electrons. The rubber on the car door might have gotten some electrons from the metal part of the car when I opened the door, giving it a negative charge. (The rubber is an insulator so electrons would not flow throughout all of it.) The electrons passed from the door to my hand, which is why I think that the zap occured. (But it's weird how my car only seems to shock me, not anyone else that rides in it.)

Flying Fish...

This was from Winter Break, and the story behind it has quite a bit of physics involved. Me and my friend were fishing on the Big Island and she caught the first fish. Since the fish wanted to get away with the bait, it tried to swim away. This caused tension in the fishing line (considering it was only a bamboo pole). However, the force with which she pulled the pole was great enough to allow it to overcome rotational inertia and begin rotating (clockwise in this picture). This also made the fish, still attached to the bait, go in a circular motion (just like the ball and string exercise in class). However, it couldn't hold on long enough, and ended up flying in a tangent and back into the water on the other side of the rocks. In the end, she lost a tasty snack, but she gained an understanding of tension, rotational inertia, and tangential vectors.

Bridge Balance

I found an example of torque just in time for the upcoming test. The bridge is really old and falling apart, but its weight is still being held up by the normal force of the ground on both sides. The weight is focused in the CM (center of mass), which probably isn't in the middle of the bridge since parts of the fence have already fallen off. The weight has to be supported by the ground, because otherwise the it would keep on falling. Besides the forces cancelling each other out, no matter where the fulcrum is, the torque exerted by the forces also have to cancel each other because otherwise the bridge would be rotating instead of standing still. (Torque is equal to forcexdistance from the fulcrum). The balance for the forces and torque exerted are the reason why this bridge stays still.