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.

torque

Like the example in my homework, I chose to talk about a light switch for this journal. While the light switch cannot do a complete rotation, it does go in half of a rotation when torque is exerted on it. To turn the lights on, the force exerted is positive, and thus it has positive torque. To turn the lights off, negative torque has to be exerted. The lever arm is the distance between the switch attached to the wall and the point where the finger hits it. As we learned, the greater the distance, the less force needed to flip the switch. This is why it would make more sense to flip the switch at its tip rather than the point closest to the wall. (Although it takes relatively little force to begin with, hitting the switch at the tip makes the task even easier to do!)

tests and washing machines

After the test, I kept thinking about that problem with the washing machine so I took a good look at the one I have at home. In a sense, the physics behind a washing machine is the same for that gravitron ride. The clothes push against the side of the machine, which results in a normal force pointing towards the middle. This normal force is also the centripetal force in the spinning action (and is equal to mass x centripetal acceleration). The holes on the side are for the water to leave at a tangent (because the water does not have enough force to keep it going in a circular motion). Also, because the motion is horizontal and not vertical, the centripetal force does not change throughout the motion. After seeing the real thing, answering the question seems a lot easier.

waikiki

I was at waikiki this weekend and as I was taking pictures of people walking on the street I noticed that the image of the cars looked really interesting. It's kind of dark so only the lights are really noticeable. Since the cars were in motion, they had kinetic energy (.5mvsquared), and since they were probably accelerating (change in velocity or direction), they also had work (change in kinetic energy) and power (change in work over time). The motor in the car is doing the work to make the car accelerate and gain kinetic energy. Even a simple thing like a car driving involves the majority of the lessons we have learned so far. If there was a collision (although I wouldn't hope to see one) then that would have involved the latest chapter we covered. I seem to notice physics in places where there are cars...

trash cans and newton

I was in Moanalua Gardens today and as I was walking in I noticed a trash canbeing held up by rocks. I don't really know why it needed rocks to support it, but I do know that there is some physics involved. The weight (massxgravity) of the trashcan and the rocks is being balanced by the normal force of the ground. The weight of the trashcan is also pushing against the rocks, which are also pushing it back because for every force there is an equal and opposite one. The forces are balanced because the trashcan and rocks are at rest. There is also only vertical forces acting upon the trashcan and rocks. Although it is strange to have a trashcan sitting on rocks, at least there's some physics involved!

Tension in the air

My mom just bought some poupouri for her car and as I was filling the little pouch with all of the beads, I was reminded of tension. As I was tugging the pouch shut, I was exerting a force on the string that added to the tension in it. The combined vertical tension of the two strings was equal to the weight (massxgravity) of the pouch and the horizontal tension of the strings going in opposite directions were equal to each other once the pouch was pulled shut. However, while I was pulling the strings, the left side seemed longer than the right side, which I think means that I pulled with more force with my left hand than my right. But then, time is used for power, so maybe my left hand used more power?