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UNIT ONE: FORCE AND ENERGY This unit is divided into ten programs. The program you're about to see is on INERTIA. Then program 2 looks at mass. Next comes speed. This is followed by two programs on acceleration, a program on gravity, then one on weight vs. mass, then work, and finally two programs on energy itself: kinetic energy and potential energy. But our story begins with inertia. Physics is about movement: how things move and why things move. Here is a very large thing. What do you notice about it? It's not moving. Go ahead and try and move it. You can't. It doesn't work to me. It that because it's so large? Try and move a smaller thing then. Well, you managed to move that a little way, but it was a great effort. It was as if it still didn't want to move. Even tiny things are reluctant to move. Even a pebble takes some effort to shift. This is the first rule of physics: things like to stay where they are unless there is some force to push or pull it. No object in the universe will start moving on its owm accord. It is as if all objects were lazy. But why is physics about movement if nothing wants to move? The answer is that there are lots of things in the universe that pull or push objects and force them to move whether they want it or not. You force the pebble to move. And since things are lazy, you'd expect your pebble to try and stop moving as soon as possible, wouldn't you? Well, you'd be wrong. Strangely enough, although, when the pebble was at rest, it wanted to stay at rest, now that it's moving, it wants to keep on moving. In fact it would like to keep on moving forever and ever. The only reason it slows down and eventually stops is because things in its path force it to stop: the resistance of the air, or a tree it bumps into, the roughness of the ground... But, if there were no air or rough ground or trees to get in its way, if you were in outer space, for example, when you kicked your pebble, it really would go on moving forever and ever. It would never stop. So how can we say that objects are lazy? If the pebble is moving, it is not being lazy, is it? Yes, it is. It takes just as much effort to stop moving as to start moving. You get a feeling for this when you're ice-skating, when there's hardly any resistance to your movement and it's easier to keep on gliding along than to stop. The same goes for the pebble. If nothing gets in its way, if nothing helps it to stop, it will have to make all the effort to stop by itself. And it's much too lazy to do that. We can now modify the first rule of physics from "Things like to stay where they are" to "things like to keep on doing what they're already doing". If a thing is at rest, it wants to stay at rest. If it is moving, it wants to keep on moving. In other words, there is lots and lots of laziness in the Universe. Physicists have a special word for laziness. It comes form latin: INERTIA.

Video Details

Duration: 4 minutes and 49 seconds
Country: United States
Language: English
Genre: None
Views: 193
Posted by: lorena3 on Oct 24, 2011

Aquest vídeo introdueix el concepte d'inèrcia, la pirmera llei de la física. A les coses els hi agrada continuar fent el que estaven fent.

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