Understanding Laws of Motion
So now what we are gonna do? We will try and see to make up some laws. Let follow the thread along people like Galileo, Einstein and Newton and all these people and let’s see if you can create some laws that the world will obey. The world around us will obey. And you already know that this chapter is called force and laws of motion. So there is a plural out there somewhere. You kind of believe that there are laws, right? You might even know that Newton’s first law, second law third law. here I am going to talk you about only one law. We will stick with only one law, first. And second also newton’s first law was not Newton’s first law. It’s like one of those little places where we all …. There light was. So let’s try to understand where all these are. Let’s start off from our old Aristotelian argument. The natural state of things is to be at rest. Is that true? Let’s say that its true. Let’s believe that it’s true. And let’s see you somebody moving. Right? This is the question that everybody had in the mind. You must stay he is in a state of moving,, there might some situation, some day, he has to come and be at rest. Someday he has to come to rest.. But what will he be thinking? He will look at you and he will say that hey you are moving, someday you will come to rest. Which of them is right? Are you moving or he moving? You stand at a train and the next train starts moving. The train near to you. Almost everybody in the world start looking out. Thinking ‘’am I the one starts moving or the other train? You all get confused. So the Aristotelian argument kind of some flaws out there because we don’t really know who is moving and the fact that Galileo began to start observing things in a slightly deeper manner than had been done before, we did realize something very very insightful and that was a huge breakthrough because he said that the natural state of things is not come to rest. We don’t know even what rest is. But, if you let some object be, it will keep going with whatever velocity it has. In other words he say, if you give a body some velocity, it will retain that velocity until and unless somebody does something to it. Now, how did you kind of propone it? What he said was- he had a very simple argument. Let me take a little slope surface and incline plane you drop a ball from it. Now, it’s gonna go down and if we keep an other inclined plane here its gonna slide down and go up there. You all know that, right? And now, let me now reduce that incline a little bit. The right one. What happens? What’s going to happen? He saw that the ball going down and goes almost the same height, where it started from. Of course sometimes it doesn’t go down that much,, we call that friction but it almost went there. Now let’s imagine you reduce the incline even more. Then it goes to the same height even now. So then he asks the question. till here its observable in reality but this where the jump from reality ti imagination comes now he said: if I make the second slope so low that its almost flat, then in order to come to the same height which the ball always wants to do, how far must it go? What is the answer? It has to go forever and ever and ever. It was an argument he gave to prove what? Or the kind of to make people understand what? If you give a body some velocity, you do observe it to be coming at rest all around us, but he says if there is no friction as they call it, what is friction? When a surface if you trying to move along- if one surface moving along another, there is some motion here, and friction tries to stop that because of some bone formation, because if its is not there, if it is very very less, he says the object will keep moving on forever ever and ever. But, just because he said it doesn’t make it true. Because most people say that hey I don’t believe it. Right? I throw this and there its stop, an you said there is friction? But then ask the question,, if there is no friction how are you so sure that it will keep going on? And are we sure,, we really aren’t. we have sent out something called the voyager into the sky right? out of space. And its kind of not stopping. But does that mean it will keep moving forever and ever? It passed Jupiter a few years ago, it passed solar system a few years ago, it has still not stop. Does that mean Galileo was right? It means that he is probably right, because if it has not stopped for long, what could make it stop later? but still people could argue that no no no it didn’t stopped for a hundred and fifty years and how do you know it won’t stop the next day? What if the natural state of things is to come to rest? The truth Is We don’t know. In other words we don’t really know we can’t prove it but the more and more we see around us the more and more we believe that if there is no friction,, things will be going on forever and ever and ever. This can be attributed to Galileo because he was the first person who had the insight who kind of pointed out it. He said no, things won’t stop. It will go on ever and ever until somebody stops them. And he said in most of our real life situations, somebody does stop them, and who are they? We call them friction. The force that stops objects, we call them friction.