 This lecture and the lecture following this will be to give you a flavor for what you are going to see in the course ok. So, the idea here is to form some sort of background for you to be able to appreciate the context of this course as part of your engineering curriculum. Why does this course exist? What are you expected to learn during the course of this semester? How it may help you? How it may help others? Those sort of questions will broad questions. We will not spend too much time on specific details for which individual lectures followed by lab sessions will be held anyways ok. So, the idea here is to get an overall sense for why this course and where it is going to go ok. So, in doing this we will touch upon a few sort of philosophical ideas, ideas that do not necessarily have to do only with this course, but surely it will have something to do with this and as well as create the grounding for you to be able to appreciate some of the statements that will be made later on in this course especially the next lecture. So, before that I am going to liven up a little bit. So, I am going to try and find out why you are here. So, multiple choice question. So, I am going to put 4 or 5 choices there and after each choice is put up there you can raise your hands ok. If you think that that statement is representative for why you are here ok. First statement I think attending classes helps me get better grades I am not asking for a vocal response I am asking for a visual response put up your hands if you believe yes ok. What is that? You can you can shout into the mic if you want. Second option is. Hello. Heard that this is a good lab course. So, want to learn. Third option is Jemta was going to Ponvo and I followed. Fourth option is I am here for attendance. So, after all this gimmickry I am going to ask for serious hand shows at the end of it and last option is I have nothing better to do ok. So, this is going to last for another 2 minutes ok. So, you can enjoy for another 2 minutes and then the rod will start ok. So, A who all say A ok put your hands down B. So, which do not you agree in this that you did not hear that it was a that you heard that it is a good lab course or that you want to learn which do not you agree. Second you move leave the class number C number D. So, most of the students are not opting for any of these none of the above also should be an option right. I got a sense for it when I first put up the options. So, we will do that ok. So, I am going to ask a few people now what they think this course is about ok. If you are if you are going to be vocal and act smart in front of your your group of friends I will pull you up ok. So, I am going to pull the guy who spoke from there speak into the mic who is the guy who spoke from there come on. Let us see if you have the guts everybody knows it is you. So, just just pick up the mic and speak pick up the mic and speak hello boss it is right there you pick up the mic and speak yeah next to you. Don't know. No you said something else come on show us your smartness. Something like measurements. Something like measurements. Guy with a blue shirt there can you pass the mic to him. You have to say something intelligent. 650 of your fellow students are listening to you. Experimentations and it is a lab course on experiments involving measurements and. So, this is what you think this course is about. So, you have gone through module I guess. Anybody else who can speak openly red shirt. Sir the lab is about the lab is about what the teachers think of the students about what they do not know and they need to know. They think that we do not know certain experimental skills and certain measurements skills yeah, but the last year's grading shows that we all know such things because most of the people got that A square in the. Okay anybody else now that you have vented all your feelings about this course somebody else. I do not have any idea actually about this, but whatever you think it is. I just read the name on the module it is all about measurements. So, what comes to your mind? First word was measurement so. Nothing blank. Yeah. Okay. One person over there I am going to pick the purple or maroon shirt girl the right there. Yeah. I think this course is about different types of measurement the way we can do measurement through computer programs and stuff probably this is just a guess. So, I am going to store these answers by the way your long winded answer also is going to be stored and we will see at the end of the course if what you are saying is right. Okay. Okay. So, now we are going to think a little bit about a couple of basic questions and the idea is to have a bit of a discussion. I mean obviously, if you are 650 you are sitting in front it is not possible for everybody to speak up at the same time. So, I am going to orchestrate the discussion a little bit right. But the questions I am going to ask everybody to think about and I will randomly pick people to answer. Okay. So, you can just chill out there and unless you want to be embarrassed. Okay. First question is why do you think we need to experiment? Okay. I am not asking this question for an immediate answer. So, I am going to say that a lot of people around you people, media, textbooks, teachers, professors, whoever they may be they keep making claims about the physical world. Okay. I am going to throw a few of these claims that a lot of different people have made at different points in time not a lot of different people. Different people have made at different points in time which have had far reaching consequences on how human beings have reacted to these claims or the scientific community in particular have reacted to these claims. Okay. So, I am going to throw a few of these and mind you I know for sure that at least 95 percent of you have not verified these claims on your own if not 100 percent. Okay. So, do not snigger at the claims because I am going to ask you to verify one of them later on. Okay. So, the first claim a falling body accelerates uniformly it picks up equal amounts of speed in equal time intervals. Okay. So, how many of you think this claim is valid? How many of you think this claim is valid? If you answer no I will pull you up and say why do you think it is not valid? Only 4 or 5 people think this is valid. Green shirt there. Tell me why it is not valid? Why you think it is not valid? Speak into the mic. Mic is coming to you. Can you put up your hand please or should I give you an arthi and say put up your hand for that? Okay. So, one more call. How many of you think this is valid? Okay. So, some more respectful souls. Okay. Second claim water can be transmitted to gasoline from extracts from a bush. How many of you think this is valid? Next claim all species of life have common ancestors. Who all think this is valid? Fourth claim speed of light as measured by multiple systems that are moving with different but constant velocities always yield the same constant value. Fifth claim a single molecular layer of organic material between 10 to 20 angstroms that behaves as a transistor has been assembled. How many of you are agreeing to the statement or you think it is valid? Okay. There are two. So, I am just going to name the people who made these statements first. Any guesses for number one? Okay, Galileo. Number two? So, there was a guy called Ramar Pillai. In 1996, he claimed that he could make gasoline by taking some jettibooty and mixing it with water and heating it up. Okay. Now, it took a lot of effort maybe for the right or wrong reasons for the Indian scientific community to refute this claim. In fact, he wrote a dossier and sent it to the prime minister's office. The prime minister's office sent it to the department of science and technology. And after that, a lot of different people could not refute that this was indeed not true. Okay. So, this is not some bogus stuff that I have just put up here. It took a lot of effort for somebody to say this is not true. Of course, it was not true. Eventually, it was found to be not true. He was trying to fool people around. Number three? Okay, Darwin. Number four? Okay. I am sure a lot of people don't know who number four is, but that's fine. Number five? How many of you think this may be true? Okay. So, I am going to pull the blue shirt. Yeah. Why do you think it is true? Why do you think it is true? Sorry, the other guy. So, I will pull up somebody else from here. I believe it is true because a lot of advancement have been done and we have also started about thin film, coating. So, I think it may be true. Why not number two? A lot of advancement has happened. Number two can also be true. Yeah. Actually, I read in the newspaper that they are going to... So, I am going to make a postulate. Okay. That is, I am going to claim the reason you think it is true is that it doesn't sound bizarre. It sounds like authentic. Okay. Anyway, so anybody else who think it is true or it looks like it is true? I know that some advancement has been done with organic semiconductors, but I am not sure of the specific details. So, I believe that it's true. This guy here. Sir, I had read about azuline molecules being used as diodes, a single molecule of azuline. Okay. So, I think... So, you read about it somewhere and you think it sounds intelligent. Yeah. Okay. One more person. So, everybody is saying the same thing. I read about something somewhere, organic semiconductor, blah, blah, blah. I have heard that a lot of advancements are being taken place in this field. Okay. The last statement was proven to be one of the biggest scams of physics of the modern era. Okay, last 20 years. So, there was a guy called Jan Enrik Schoen from Bell Labs who published a series of articles in very reputable journals claiming something to this effect. Okay. This is not an exact statement, but the different statements put together claims something to this effect. It was shown to be a lie. A lot of different people tried to replicate this experiment, found that this was a lie. So, till now nobody has done this. Okay. Just that it sounds cool. A lot of people got fooled. Okay. Just because I say organic material, single layer, molecule and all that, people think... Okay. So, these sort of statements keep getting thrown at you. You keep reading stuff. Some guy in Times will report in the technology section that, you know, researchers somewhere have found out that this has happened, blah, blah, blah. Right? Then professors come and tell you or your teacher in your 11th or 12th standard would have told you something about number one, falling body accelerates uniformly. Okay. I know that almost everybody, even though you didn't put up your hand here, you believe that this is to be true, number one to be true. Whether or not you know if it is true, you have got through your JEE because of this. Okay. So, now I'm going to ask one of you or again two or three people to say why they think number one is true. First of all, do you think number one is true? Yeah, it is. Why do you think it is true? Because I have learned that from my sixth class. So, suppose I type number five. I know I'm telling you number five is not true and you can go and check it that number five is not true. I type number five in your textbook nicely and put it up there and told your teacher to keep repeating it. Do you think it is true? Never thought about that. No, I'm asking you to think about it right now. Suppose number five appears in all textbooks of 11th standard. Will you believe it is true? Okay. So, one person from here? Basically because mostly professors and all tell us this stuff. So, we think that it is true. What? What? What? If you are told to don't touch a tiger, so you will never say hi to a tiger. Okay. Okay. So, like this itself, we have been taught this way that when a body falls. So, are you saying this statement is like a tiger? Sir, will you just like for fun stroke a tiger? I'm not making a claim. You're saying stroke a tiger. I'm making a claim that you don't strike a tiger or make fun of him. And I'm telling you, I'm warning you. So, will you go and strike him? All those who clap, all those who clap in celebration of irreverence, right? You're missing the analogy. There is no analogy here. Okay. I'm not asking you to do something dangerous. Right? I'm asking you to tell me whether you believe something is true or not and why you believe something is true or not. And your answer is that somebody has told me I'm not going to question it. That is your answer. Okay. That's fine. Anybody else who has a different take on it? That isn't true in the presence of air resistance. Why are you making this statement? Sorry? Why are you making this statement? Who told you that this statement is true? See, in the presence of air resistance, one can see that it's not true. One can see means what? I can't see. If you drop a feather, it floats down. It doesn't fall down with constant velocity. Is it saying that it does not pick up equal amounts of speed in equal intervals of time? A feather, if you drop it here, it won't. How are you saying that? I've seen it. You've seen it? Yeah. You've actually measured speed? No, but the difference is measurable enough. The difference is visible. You can see that it slows down. If you drop a stone, then it falls down at once and if you drop a feather, it doesn't. No, but I'm saying something more. I'm saying that it gets equal increments in speed in equal intervals of time. Are you going to make that conclusion by dropping a stone and observing just with your naked eye? No, sir. Anybody else with a different take on it other than my teacher told me how I have read it in a book or my J.E. classes had me to do this, other than these three things? If everybody was like you in 1600, Galileo would not have had a tough time. He says something, everybody believes it. Now I say something else, you will believe it. Unfortunately, this is never the case. If something material shows up that is going to change your belief ground up, there is always resistance to taking the claim as being true. And this is exactly what happened to Galileo. They did not think nobody thought that this was right. And Galileo had to fight against the church. He had to hide his statements like this before it became reality. Nothing has changed in those 400 years as far as human attitude goes. It is exactly the same. You guys are just like the people in 1600s who all thought the world was flat, was flat, because everybody else was saying the world was flat. Masters, teachers, everybody was saying world was flat. Nobody is refuting that. So, nothing has changed. This is a living example that things have not changed in 400 years. So, why should we conduct an experiment? So, people keep making claims for your own curiosity. You need to verify if those claims are valid or not. That is one of the main reasons why people conduct experiments to find out if what somebody is saying is really valid or not. And all of you do this in some sense or the other, except that the claims that excite you are not all these claims. They are something else. Now, think about it. If I do not work so many hours, then I will not get into truth JEE. You do not want to test that claim even, right? You are scared. I should work for 10 plus hours. So, the whole point of doing an experiment is to be able to assert and if claims are valid or they are not valid. Being able to arrive at logical conclusions of whether a claim is valid or not. And you are training yourself to become an engineer or a scientist. So, you should have some exposure to validating or invalidating claims that are made about the physical world of the sort that we saw earlier. You may not be in a position to conduct an experiment given the background, given the sort of sophistication you require to test some claims all by yourself, but you should appreciate what goes into the conduct of such experiments. And so, this introductory course is meant to give you a feel for the sort of issues that you will face in the conduct of any experiment. And specifically to give you a feel for how to go about conducting some experiments which are tractable, which can be done over the course of a semester. By means of which we hope to be able to get you thinking about some of the issues pertaining to experimentation in general. This is what this course is all about. It is not about writing some computer program. It is not about building with some electronics. Now, during the course of the semester, as it often happens, you may lose track of this. You may lose track of this intent of the course because you get involved in a lot of details. So, let me give you an analogy. Suppose I want to make excellent paneer tikka masala. That is my intent. Most people here cannot make excellent paneer tikka masala. But suppose you had to make it. During the course of making it, the whole idea is to have excellent paneer tikka masala to eat. You have to serve somebody else who you want to impress, let us say. But during the course of it, you have started cooking. You get involved with jeera, etc. So, you get involved in that and you think that is what the whole deal was about. How much tomato to put, how much onion to put, etc. So, you are going to end up having to do that because unless you do that, you will not get an appreciation of the whole deal. But the point of the course is for you to get a hang of what does it take to conduct a good experiment. At the end of the course, you should be able to make a mature statement. Hopefully some of you will be able to do this, that this way of conducting an experiment seems okay, this way doesn't. If somebody posed two ways of doing an experiment. That is what this course is about. So, very briefly an experiment is just a procedure. It is a recipe. It is a procedure to verify whether a claim is valid or not. Now, how you construct the procedure is the most interesting part of the experiment. Because the procedure, what you observe after you conduct the procedure, you should be able to logically conclude whether a claim is valid or not. Suppose you conduct a procedure from which some observations come, but they are not related to your claim, then your procedure is wrong. So, it is a procedure to validate a claim. That is what an experiment is. Okay? So, hopefully that gives you a bit of a background for what we are attempting to do here. Now, there is another reason for why the course is going, you are going to see the structure of the course as it is going to get unfolded. There is a reason why we have structured the course the way it is structured. Is that it is also an attempt to undo a historical mistake in our teaching methodology. Nobody here has ever validated a claim that you have used so extensively in all your physics. Okay? So, it is crazy. From 650 supposedly smart people all say, okay, whatever somebody tells me is right. Okay? You do not carry this attitude to something else. Your irreverence is shown in a lot of different ways. Hero. But your irreverence is not shown to people or to claims that are made and put in front of you. Okay? So, the idea is also to get you thinking about this. That you need to be irreverent about claims that people are making. Not people who are standing here and lecturing something because they have to. Right? Think about it. Okay? So, we are going to challenge Galileo. We are going to take a few volunteers from the audience. Seemingly, nobody has ever challenged. So, I am going to ask you. A lot of people have come here without notebooks and all that. I say, But you are going to borrow a sheet of paper and a pen if possible. And you are going to conceive an experiment right now with how much ever little you know. It's okay if you do not know how to construct an experiment. But I want you to conceive an experiment where you are going to tell me at the end of the experiment confidently whether the following statement is right or wrong. Okay? A following body axle. It's uniformly. It picks up equal amounts of speed in equal intervals of time. So, now I am going to give you three to five minutes. It's your choice to fool around at the risk of being pulled up. I know who is pulling around. So, three to five minutes for you to think about it. Jot your stuff down in a piece of paper. Okay? I want you to be doing something. Not showing attitude. I can also show attitude. I am going to ask for the sheets and I am going to read it out with your names on it. Put your names also on it. So, look. So, let's see your, your gam. Some people have drawn some pictures. So, I am going to ask them to come and speak. Okay? I am going to read out some, some answers. Okay? I guess you did not understand my question. I said conceive of an experiment which means conceive of a procedure by which you will verify if this is correct or wrong. Who is Vasudev Pallival? As we all know, gravitational force is GMM by R square. Therefore, this is, this is true. Prashant Gen, a pulling body accelerates uniformly. Delta V proportional to delta T. That is what I have to prove. Okay? This is a little better. Somebody is actually describing a procedure. Throw a stone. This is Shipra Agrawal. Throw a stone. Pictures with a high speed camera at different times. Okay? Measuring distance covered in equal intervals of time. It is not distance. We are talking about speed. Rishabh Agrawal. The claim is correct since the given body uniformly accelerates. There is nothing to laugh or cry. You would not have done any better. I say bhajare ho. Avnish Kumar. Acceleration means change in velocity per unit time. However small the time interval will be. So uniformly accelerating body gains equal amount of speed in equal intervals of time. Okay? Again, you do not understand the statement. Why is the falling body accelerating uniformly? Or is that correct or wrong? If it accelerates uniformly, what you are saying is right. Nithish Reddy has shown a inclined plane. You want to explain what it is? Given the, given mic. What I am doing is using a light source that would cast shadow of that ball on a flat surface. So I would plot the distance x with time. And with that time, I will use the slope and all. So what? How will you use the slope? I will get a graph of x versus t. Okay? So at least you are trying to get a graph of x versus t experimentally. You want to roll something down a slope, shine some light. No. That is not a slope. That is actually a ball falling and light source. Light source and you are going to project it against something. No. On the wall. On the ground. On the ground. Okay. I did not get it. But anyway, that is fine. Nishant says if a ball is dropped from a height h and if indeed it is accelerating uniformly with acceleration a. Then we will have a relationship of the form t square proportional to h. Okay? So drop an object from heights 0.5 meter, 1 meter, 4 meter and note the times. We can assert the claim. It is pretty good. So the only guy out of if this is a random sample, 6 out of 5 out of 7 seem to be writing some equations down. Right? There is no equation yet in this claim. Okay? Of course you can interpret the claim with some equations. The idea of the course is not that. The idea of the course is not to do things on paper. The idea of the course is to describe a procedure that somebody can actually perform in front of you. Sometimes you will do it. So we are actually going to perform the procedure that Nishant has proposed. Okay? And we will see why it is difficult to perform the procedure. So we are going to follow this procedure. Drop an object from heights 0.5 meter, 1 meter, 4 meter, etc. And note the times it takes for the object to travel that distance. And if the relationship t square proportional to the h holds, then you are pretty much there. It is not really there. Actually this is a corollary of this statement. Okay? And I am glad that you preempted me. In fact, the next slide is that. So we will show this corollary. Okay? So D1, D2, D3, the total distance traveled by a body in free fall in times 0 to 1 seconds, 0 to 2 seconds, 0 to 3 seconds are related as 1 is to 4 is to 9 is the claim. Very similar to this. The t square proportional to h claim. Okay? So this is the claim we are going to verify. Suppose you had to verify this claim and you had to follow this experimental procedure. Drop an object from different heights and note the times. I want you to jot down again what you think may be the problems with such a procedure. Right now, from a layman perspective, give whatever the hell you think makes sense. But I want to see English words, not some scribbling of some numbers. I want you also to do it. Again, please come down from your high pedestal. You have graced the occasion. Now please write something else. Again, 2 to 3 minutes. I want you to write English words and why you think or what the issues with the described procedures could be. Just from a layman perspective, something your mother or grandmother can say as well. And if you have a perspective different from that, add that also. Just a couple of sentences, phrases that you think may be issues with the experimental procedure. Why you think you may not be able to carry it? Carry it out. So some of the issues, dimensions of the object used. Ideally, we would consider a point object from same defined point. Second issue, errors in measuring time of fall, apparatus and human errors. So I assume that, so who is saying this? So, Tanashree Prasad. So you are assuming that some human being is sitting there with a stopwatch and Chalukarobi and Girgaya, stop it. That's what we are going to do now. Someone says the height, even a height of 3 meters is as tall as a normal room. And as the height increases, the accuracy and the ease of the experiment suffers. Time lag in responding to start-top motion of the ball. That's the second issue. Someone here says inaccuracy in the measurement of time and air resistance. So, pretty much, I mean most people can guess this, the tough part of it for a body that is falling under free fall from the normal reflexes that you see in human being. And if indeed a human being is timing it, it will be the actual act of timing it. Things happen too quickly. So you can do your mathematics. 2 meters is going to take around 0.6 seconds, 0.6, 0.8 seconds for things to fall down. Human beings tend to find it difficult to respond in that time if you are sitting with a stopwatch. Someone has already pointed this out, this issue, that you will use a high speed camera. Last time around, if you can take snapshots with a high speed camera, then you will be able to do a better job. Obviously all of these are correct. So the main issue is with regard to measurement of time, accurately enough. This is in fact the same issue that Galileo also faced. So now you are on par with Galileo. So how do you resolve it? Galileo resolved it in a certain way. We will resolve it in a different way during the course of this semester. And in fact you will get this uniform acceleration number also. In other words, you will get an estimate of G. You could use a horizontal beam of light and use a body of some length L. Then we use a device which measures the time for which that beam of light has been stopped by this body while falling. This would be more accurate because this involves light which travels fast. It involves light which travels fast. I mean the sound travels at a pretty low speed, so there could be that error as well. I won't consider time like one second, I will just fix the height. So that's what he has said. I will fix the height. Maybe I will put a string string string and attach it to a clock, a manual clock. Manual clock? Something sort of that. Some string which will go and pull a clock. Yeah, to stop it, sort of. Okay. And when it hits. Anybody else? In real time you came up with something, I feel like. I was thinking more on the same lines, the fixing laser beams at a particular height. And then when they intercept the light it's electrically connected to some kind of a device which stopped. Okay, so you are going to pretty much do, you won't use lasers. But you will pretty much do this during the course of your experiment in estimating G which will involve electrically coupling. Okay, something which gives an indication of whether the object has passed a predefined point or not. Okay. And be able to use a clock which you can measure precisely. Whose clock beat you can measure precisely. Avoid human beings doing this. So you will end up doing that. I think somebody else also mentioned something similar. Any other way? This is not what Galileo said. He did not know anything about, or he think he did not know anything about microcontrollers and all that. Okay. So firstly I don't believe this claim to be true because if gravitation decreases as per square of distance, then whatever we say that if we say that a body is going with constant acceleration, it's just because our experimental methods are inadequate to prove that the acceleration is not constant. Fine. But if you do not observe otherwise, why will you believe otherwise? Sir, like in case of satellites, or let us say there's a moon which has been revolving around the Earth for millions of years, like if gravitational acceleration... What about if the moon is going around the Earth? Have you ever seen the moon go around the Earth? It just appears there. Some things we have to take for... I'm not asking you to assume anything here. Can I answer this question without assuming that the moon is going around the Earth? Sir, actually I feel that the problems in this experimental method, like whatever we do, if we let us say drop an object from a kilometer above and even in an evacuated space and then we observe and maybe from 10 kilometers above, then we would observe a difference. You will not get this result by the way. You will not get T square proportional to H if you drop it at 1 kilometer. Yes. So you say it is invalid and move on. The idea of the experiment is not to say that this is correct. The idea of the experiment is to find out if this is correct or wrong. So yes, what you are saying is right. Any experimental procedure we come up with will have shortcomings. Maybe we could roll a ball with horizontal velocity. You can roll a ball with horizontal velocity and let it drop and we will measure the height and distance it has dropped from the wall. Height and distance it has dropped from the wall. We will be squaring and checking whether it is proportional to the height it has dropped or not. But why are you separating the horizontal and the vertical? If, I mean if we assume that it does not have any horizontal acceleration and only... Who told you that? Who told you that? So this was part of the thing I wanted from you. So you are all conditioned to think in a certain way. Only MG acts when it is in free fall. This is the force and therefore you have an acceleration. Here we are not talking about all that. There is no notion of force here. We are only trying to verify if some statement is true by pure experimental observation. So we can perform experiment very large number of times so it reduces human error. We can perform experiment of taking time at different time intervals and measuring distance. Let's take one statement you made. By performing an experiment large number of times do I reduce my error? Sir, suppose I have to make my calculations up to height to edge. So then what I will do? I will put a thread and attach to a stopwatch to that. And when the moment the ball crosses to edge it will just cross... It have to cross the thread. So it will throw the stopwatch will get on and for the sake of... For counting the error I will just let the ball go up to 3 edge. Okay. And... You use a stopwatch and a string attached to it, right? Yeah. Then to the right. When the ball reaches up to the height 3 edge I have its time. Okay. So from the total time I will subtract the stopwatch time. I will get the exact time. Okay. So now this guy sees that many Bola string you should attach to a stopwatch. He has taken my idea. So somebody else says you will use an accelerometer. What the hell is that? Accelerometer is something which measures acceleration. Okay. We could have just said use a speedometer. Speed measure is done. Yeah. So why not use just some accelerometer like... Why accelerometer? I will use speedometer. I am not familiar with speedometer. So I told accelerometer. Okay. So I expected these sort of answers. Most people when they have to measure speed... Sir. Fix certain tolerance level with the result and if the calculated result is within that level then you accept the claim or else you reject. Okay. That is the way you will accept or reject it. We are talking about the procedure. So I have never seen an audience of 650 people all throwing a bang on there. Hello sir. So I am very glad. I think you drop one stone just after one second drop another stone. Just after that one second drop another stone. And take the recordings of the stones while hitting things. That will reduce all the manual errors in each of the stones. If you drop multiple of stones. Who will tell you what is one second? That is your normal clock. That will reduce to a very large extent. Okay. One or two seconds depends. Make a tower of height. Large height. So if you want to reduce the error we can increase the height. Instead of taking... Yeah. That's the same idea. You can drop the object on a watch. So when it hits the watch the watch will stop working. So we know the exact time. What is it again? I didn't get any of the things you said. You have to repeat it because it was so far. You drop the object on a watch. So when it hits the watch the watch will stop working. So that way you know the exact time of impact. When did you release it? How do you know that? Sorry? When did you release it? How do you know that? You only know the time it broke. But you need to know the time it elapsed. Sorry, your answer is not right. So drop the watch. So not this original but actually there is a story like that. This is about Rutherford. Say I hadn't read it. No? Say I hadn't read this. Now I know you have read it. Read it? Okay. Very good. Very smart guy. Couple of minutes on this. Rutherford's bore thing. So maybe I'll post it online. More fun reading it than me saying it. Okay. So apparently some of you have said use some sort of a solution where some beam of light or some source of something is interrupted and if you are able to measure time accurately through whatever means it may be then you will be in a position to make an estimate of whether this statement is true or not. Okay? Or you will be able to conclude confidently whether this statement is true or not. Okay? That's pretty good. Some others have said that increase the length basically. Increase the distance. Therefore you have more time. And therefore human errors play lesser of a role in you deciding whether the statement is true or not. Which is fine. Which is what I would have sought most people without an exposure to electronics would say. And in fact that's the same thing Galileo also thought. Okay? So Galileo said that we will build an inclined plane instead of letting it drop straight. And he made a very interesting observation that the speed of the ball whether you drop it or whether you roll it down an inclined plane as long as it is covered the same vertical distance happens to be the same. Okay? Assuming there is no friction blah blah blah. The speed remains the same. Not the vertical component. So how did he infer this? He constructed two inclined planes. One with higher elevation, the other with the lower elevation and saw that the ball went to the same height more or less. So obviously the speeds that it started off must have been the same. So this observation he made without any understanding of forces. Nothing. Just an observation. Okay? Therefore he said I will conduct the same experiment on an inclined plane because the speeds are lower or it takes more time to reach speeds and I can use sort of stopwatches sort of things or pulse beat which is what people knew to find out if such a statement is true or false. Okay? So he in fact did that. Built an inclined plane, tried to make things as smooth as possible tried to reduce friction or the effect of it used pulse beat to more or less confirm that what he said was right. Okay? Which formed the basis for what Newton did later on. Okay? So it's a remarkable experiment. It's actually a historic experiment. We would not be sitting here and talking about satellites, moon going around the earth, sun, all that. Had it not been for Galileo who thought about this at the right time. Okay? Or at the time he did. So it's a remarkable experiment but fairly simple. But the observations are very important. Especially the observation that the speed does not change. I don't think too many people would have made their observation if they did not know enough mechanics, a priori. Okay? So we'll leave it at that for today. So the idea, don't mind up. Okay? I have two more minutes. So the idea of this course hopefully has gotten communicated to you. In the process you will have to learn cooking. Right? You will get exposed to how modern experiments are conducted. And for that you will need to be exposed to electronics. Without that exposure you will find that you are not using the right tools to do the right thing. Okay? So suppose you had to turn a screw inside. You did not have a screwdriver. Or you did not know that a screwdriver exists. You will say I will only hammer it or I will use my hands. That's not the right way of dealing with it. So part of this course will expose you to some of the tools that allow you to perform experiments in a modern setting. Okay? And part of the course will try to allude to these sort of questions that have been raised. Okay? All our discussions pertaining to the course will be other than the lab, lectures, blah blah, will be done through Moodle. All announcements will be through Moodle. It's your responsibility to take care of the announcements. A preliminary info about the course who's teaching it when it's going to be taught some sort of what labs are going to be used as well as the grading scheme has been put up on the site already. More information will be continually be put. Okay? So it's your responsibility to make sure that you are on Moodle and you get the information that you need. I'm going to have two minutes for some questions. If anybody has questions, put up your hand. Otherwise, we move on. Can we bring spring balances? Can we make use of spring balances at your own will? We will give you what we have. That will give us a rough idea that it's independent of height and all that. The point of the course is not this experiment. You will do a lot of other things. This happens to be one of the things that you will try out after you are exposed to some tools. Any other questions? You will be exposed to more fun things than spring balances. So we are done for today.