OL/IGCSE Physics: All about ATPs (Paper 4) Part 3

Added: 2026-05-15

[00:01:55]Come on, Assalamu Alaikum, let's start.

[00:02:04]Well, our aim today is that we will now be looking at the left over type of questions which were the general physics questions that we haven't seen yet.

[00:02:14]So we will talk about that a little bit and we will also talk a little bit about this today.

[00:02:20]It is the idea of ​​the line and the curve of basefit. Obviously, not everything in ATP can be done online. Which is why there is the Inpurse Workshop at Crato College on the weekend Friday, Saturday, Sunday.

[00:02:36]So for this reason, we will talk as much as we can here right now.

[00:02:41]We will discuss the rest later in the physical workshop, Insha Allah.

[00:02:43]Planning Questions I'm Not Going to Do Because I Feel Like the Video Is Good Enough. And if you look at it properly, many things will become clear.

[00:02:51]But in the physical classes I will be going over this. Well, I have kept some points of General Physics open here, where if needed, we will be referring back to this. Well, in what ways do we get questions in General Physics recently?

[00:03:08]Sometimes questions related to speed come from chapters of kinematics. Sometimes they come for moments, sometimes they come for density measurement.

[00:03:15]And basically yes, this is how it comes.

[00:03:18]Like springs have appeared in recent papers.

[00:03:20]So more or less, this is how you get General Physics questions. So let's now start trying out some of these.

[00:03:32]Now like it is but again that's af. So let's come back to this later.

[00:03:43]Again, scale measurements are also what we will be doing in the expansion workshops.

[00:03:49]So let's look at another question.

[00:04:02]This is also scale measurement.

[00:04:11]Okay, let's look at the recent ones, let's take an example first.

[00:04:15]To 24 Do Something From 2025 Okay so let's try to do this again I've never seen this question before.

[00:04:39]OK so this is a cave of best fit but it's fine. We had a line yesterday. No, let us try this question. Okay, so this is 725 paper 41. Let's start looking at this one.

[00:04:51]So the question is asking the student to investigate a time taken for water to flow through a small hole in the bottom of a can. The apparatus is arranged as shown in 3.1 and it said that B is your 100 cm measuring cylinder, funnel, small hole, 50 cm B is the measuring cylinder and so on.

[00:05:09]So, the student uses the 100 cm measuring cylinder to measure a volume V of 70.

[00:05:16]Places a finger under the hole at the bottom of the can.

[00:05:20]Ok? Here and he's saying that then after that pour the water into the can from the major cylinder. Okay, so it means it pours water from here to here in this manner.

[00:05:34]And then he is going to remove the finger and at the same time start the stop watch.

[00:05:39]Records a time T1 when the volume of water collected in the measuring cylinder is given by cm cube. Stops the stop watch.

[00:05:46]Well, when you are reading the question, it is a very good idea in the procedure that you also think critically about what is happening, how is it happening, is there a better way to do it or not, like suppose if I think here and you yourself think by putting yourself in the student's issues, then it is not very easy to remove the finger and at the same time start the stop watch. So keep this in mind right now that if the examiner asks you further, tell me any source of error. So this is something. Right? Apart from this, here the way it is, when it is going to, when he is going to remove the finger, then it is also possible that some water may get stuck to his finger. So again these are some sources of errors that can happen. So you're already thinking about it.

[00:06:33]3.2 shows the reading on the stop watch at time T1. Record T1. So, this is seconds and this is 1 second. That means 63 over 100 which is 63, so what is the time taken? Straightaway 22.63 seconds. Here you have no reason to be rounding. So please do not do any rounding. You have to record it exactly as it appears. Correct?

[00:07:01]Well, what does he say next?

[00:07:04]Student repeats A1 and records the time T2 as shown. Record T2 and find the average time TAV of T1 and T2. Give your answer to the nearest 1 second. Okay, so it is coming out to be 21.84 and accordingly it is again saying to calculate the average.

[00:07:21]Well, I have told you guys repeatedly to write waking. So this is 22.63 here and this is 21.84 and you have to divide this by two for the average. So luckily I have a calculator today. So we take the average of both of these. So 21.84 + 22.63 added divided by two. So this is coming out to be 22.235, but it said answer to the nearest one second. Ok? So, I have already told you the reasoning as to when to see what. Here the principle of calculation is four SF. This is four SF. So you should answer in Ah Principle Four SF.

[00:08:19]But now you listen to the examiner.

[00:08:20]Obviously you have to listen to it. You have to listen to him whenever he says something.

[00:08:26]To the nearest point one second. Meaning I looked at the next decimal place is not five or greater.

[00:08:30]So this is just 22 like this. Ok? Give me a second.

[00:08:47]So it comes to 22.2 The average rate of flow is given by R which is 30cm / TF Calculate R and give the unit of your answer. So you can also see that this is cm.

[00:09:00]This is seconds. So what will the units be?

[00:09:03]cm per second pretty easy. And then just 30 over the value.

[00:09:10]So if you use 22.2, it comes to 1.35.

[00:09:14]So you can write it as 1.35 or you can also write it as 1.4. The examiner will accept both.

[00:09:20]Writing more SF is not the issue.

[00:09:22]Writing less SF is the issue.

[00:09:27]Student repeats A1 and A2 for values of V equals 100 cm 90 cm 80 60 and 50 The volume of water collected in the measuring cylinder under the can is 30 cm for each value of V. Readings are shown in Table 3.1. Complete the heading with units in the top row of the table. Add your readings from A1 and A2 as well. Calculate the average time for each set of readings. So we did it for 70, so you can see that these are the times. Right? And then it has also taken the average of these times. And he is saying that you should also take this out for every set of readings.

[00:10:05]So we know that when we create columns, when we fill a table, while filling a table you always keep in mind that the unit of your column should also be r. So we said volume this is in cm. This is your first time which is t1 and you will write it like this t1 seconds. Then the next thing is your second time t2 seconds. Ok?

[00:10:41]And then the third one t3 seconds. Well why t2 not to the nearest point one? Son, this is because you are not calculating t2.

[00:10:52]You are watching t2, right? So you should look in the manner the examiner has asked you to look.

[00:10:57]He told us about rounding in T F, in T average, so you did rounding there. This is some 25 paper 41 all right.

[00:11:11]Well, now you see that brother, we have to find the average and we also have to add the old readings. So what were our old readings? 22.63 and 21.84.

[00:11:23]So 22.63.

[00:11:26]Well, here you can see that everything is written like this, basically in one decimal place, so you can write it here also in the same way, 22.63 and 21.84, so you wrote it as 21 8. Ok? You have already calculated its average.

[00:11:48]So if you try 22.6 + 21.8 / 2 again, the answer will be the same.

[00:11:55]22.2 with these rounded off values ​​as well.

[00:11:58]Now you take the average of the remaining rounded off T1 T2. So the average of 16 and 16.2 will be 16.1. 16.9 + 17.4 / 2 so it comes to 17.15. But you have to remember that the examiner had said that give it in decimal place. So this will become 17.2.

[00:12:24]This is what the examiner had said here, to the nearest point one, that is, you have to give the answer in one decimal place, then you came and then you did 18.9 + 19.7 / 2 for the rest, so it is coming out exactly 19.3.

[00:12:41]So 25.3 + 25.9 / 2 is also coming out to be exactly 25.6.

[00:12:49]Then yes my bad sorry it should be t average and then the average of 31.1 and 31.3 becomes 31 2. Ok? Well now it says on the grid provided in 3.4 plot a graph of t ai on the y-axis against v on the x-axis you do not need to start your axis at zero zero. Dr. The Curve of Best Fit. So we have already talked yesterday that brother, as far as your question regarding graph is concerned, what are the important things in it. First the axis labeling, then the units of the axis, then your choice of scale, then your plotting of the points. Right? These are the most important things. So, basically the axis labels and units, that's your first mark. Ah then a good choice of scale that's your second mark.

[00:13:40]Correct plotting that's your third mark. And only the fourth mark is for your correct graph.

[00:13:44]So you should give due respect to other things also.

[00:13:48]Well, he said that it is not necessary to start from zero. Whose graph should be made? Average t on the y axis and v on the x axis. So first of all come and put its labels here. Score the marks that you can easily score. So on the y axis is t average slash seconds.

[00:14:08]Well, whether you make this arrow or not, it doesn't really make a difference.

[00:14:13]So twelfth seconds and this is your v cmq.

[00:14:21]So here we go v cmq. Ok? So you have picked up one mark.

[00:14:28]Okay, now you have to see what scale should I select. So on the horizontal axis it's very easy to see that your V is going straight from 50 to 100. Ok? And let us talk about your TF axis.

[00:14:46]So it's going from 16.1 to 31.2. So I can say that friend, it is going from 16 to 32.

[00:14:53]Right? But again I will have to see what my values ​​actually are? Do I have so many boxes that it allows so much plotting? So we always see in the marks scheme that the examiner says not awkward scale right. So even if you are not starting from zero, you should start with a good number. Not from a number like 17 or 29 and then the value of each box should also be some strange number so that you have trouble seeing those small boxes.

[00:15:21]So it cannot be done this way.

[00:15:23]Ok? So 16 to 32 or maybe a more sensible choice would be like going from 15 to 35 on the y axis. So now let's try to play around with this first with the y axis.

[00:15:35]Let's say that if we start from 15 right? If I do that from 15 it becomes 20. Right? Let it become 25. And again this is just experimenting at this point. Let it become 30.

[00:15:54]And it becomes 35.

[00:16:01]Ok? So if I zoom out and look at this. So this is actually not a very good choice. Why? Because your examiner says that you should use at least half of your graph properly. So this is not a very good choice. Ok? So let's see if there is something that we can do better.

[00:16:22]Okay, so if we do it like this, let's start with 16 and this is again we are just trying to see what works best brother, suppose I started with 16, right, and if I started with 16 and I go, okay, what words, let's see, let's make this 18, let's make this 20, let's make this 22, let's make this 24. I do n't think all your data points will be available here.

[00:17:00]Right? So again let's rethink about this.

[00:17:04]Let's rethink our choices.

[00:17:09]We have kind of a weird set of values ​​but still we have to do it.

[00:17:16]So if we start from 15 and suppose I have to go till 31. Right? So if I do this from 15 to let's make it 20. Let it become 25 and but then we will miss our last point.

[00:17:38]Hum and again drawing with the 16 starting with the 16 it's not actually the best idea.

[00:17:48]Ok? An examiner might say that these are awkward scales. Ah so I think we'll just have to stick to what we know if this is 15 or even if we start with this 16 then we can say that suppose this is 16.

[00:18:06]So what did we say? It was 15 and then 20, right? Let's say if this is 16, 20, 24, let's say if this is 20, 8, let's say if this is 30, then friend, this is like slightly better than this because see, we are using this much till 31.

[00:18:28]Meaning, if you zoom out and see, I am using this much graph.

[00:18:32]Ok? Well, now there is one thing we can do.

[00:18:36]Right? Let me just double check. Or Seems Fine. Well you don't even there is no mark for like labeling all the way. Nothing like this happens.

[00:18:46]Label as much as you need to use. is enough. Good. And But It's Better That If You Label It All The Way.

[00:18:53]Okay, going from 50 to 100 on the horizontal axis.

[00:18:56]So let us complete this first. This is 36 then.

[00:19:05]Ok? Well, the horizontal axis is very easy. So we have to start from 50.

[00:19:11]Let's say this is my 50. 50 The first reading is 16.1 okay? And then I should do 50.

[00:19:20]This is 60 and this is 70 80 but it is going up to 100, right?

[00:19:30]We divide it into half and half.

[00:19:37]Or you can also like probably start from 40 here. Right? You will say brother this is 50.

[00:19:47]This is 60. This is 70. This is 80. This is 90 and this is 100. Right? So whatever your useful readings are, it's using our a pretty good portion of the graph. This 110 this 120 is fine. Now let's come to 50, we have to plot 31.2 is correct. 50 for 31 Oho what is happening to him brother?

[00:21:02]Can we start from five? Well son, there's not really that much advantage to starting at five that you might think if you I'm assuming you're talking about the t axis. Right? So, from five to 16, nothing will come between you.

[00:21:16]So then when the examiner has given you a facility of not starting the x-axis from zero zero. So then you didn't take any advantage of it, did you? Meaning if you are starting from five then you should have started from zero. Are you understanding the point? Oh! That is the matter.

[00:21:33]Okay, now we have to plot 50 31.2, so see, this is 30. This is 50 so 31.2 31 will be here. 31.2 will be here. Ok? So this is your mark. Ok? Okay then it is 60 25.6 25.6 so this is 26 so this means this is 25 so 25.24 6 came here like this.

[00:22:11]Then your next one is 70 22.2 here it is.

[00:22:21]70 22.2 and then the next one is yours 60 25.6 no wait a minute 70 22.2 so that's it and the one after this is 80 19.3 80 19.3 3. So this must be 18 this is 19 19.2 19.3 okay? Here it is and then here is your 90 17.2 so this is 18 this is 17 this is 2 and then here is your 100 16.1 100 okay? The choice of 100 became a little difficult.

[00:23:19]See Now This Is a Problem When You Start From 16 See 16.1 Coming Here. Correct? So it's a bit weird to plot here.

[00:23:30]If I lower it a little bit.

[00:23:36]Ok. Well I don't get if we do it from zero won't be able won't be still be able to fit y axis till 30 plus seconds. It will be a son. It is not an issue. But the problem son is that you should think that if you do 30 then it will come.

[00:23:52]But you should think that your graph will become very weird. From zero to 16, let's say your 30 mark is here. Right? So I'm assuming that 15 is here again. So it means nothing will happen to you here.

[00:24:04]This will be an empty space. Your graph might be forming like this. So it means you did not use the graph properly. Are you getting the point? When you plot a graph, you want to use as much of the graph paper available as possible. This is the issue. Okay, when we talk about drawing the curve, so look here is my 1 2 3 4 5 six point. Now you guys can't see it.

[00:24:28]But I've turned my iPad around.

[00:24:30]Because I am a writer. So what I will do first is in the air I will see how my hand will move to draw this ah to draw the skirt. Right? So first I will show the movement of my hand once.

[00:24:43]I'll just trace on the paper how it's going to rotate and then once I've done it a few times in the air I'll complete it with one smooth movement.

[00:24:53]So now let me first rotate my hand a little and see how it will rotate. Son your should go through and through this is too much obviously. So you think now this is getting somewhere.

[00:25:06]Ok?

[00:25:09]Basically something like this and now once I'm kind of perfecting it I'll try to create this with one smooth movement. Ok? Now This Is You Might Not Believe Me But This Is Actually Hard to Do on the iPad. You pick up your sharpest pencil and you try to draw this now. So you caught it.

[00:25:35]OK not the best. It's like this looks something like this is kind of fine, right, not the prettiest curve ever, but it does the job, and the examiner himself knows that if the child is making a curve, there is some scope for error in it, as opposed to a line where his requirements are a little more strict, he understands that it is difficult to make a curve. But you have to take care that you draw one smooth line.

[00:26:07]Right? And as close as possible to the points. So, even two, ah in reality, ah may be I would have wanted it to probably be a bit closer to this. May Be Slightly Closer to This If Possible But Whatever It Turned Out to Be, It's Good Enough. So, this was the last part of it. Okay, now it's saying Suggest Why Times t1? Sorry not the last part.

[00:26:30]Here he has asked something further. So suggest why the times t1 and t2 for values ​​of v below 50 are not measured. Ok? So he is saying that if the value is below 50 then why not use it? So brother, if you are using values ​​below 50.

[00:26:50]You can see that it will take more time.

[00:26:51]Right?

[00:26:54]And you also think a little that having more time is not such a big issue. You are using a stop watch. The Major can do it. Let's go back to the experimental procedure. So if the value is less than 50 or more than 50, what is the issue?

[00:27:12]Brother, you cannot do more than 50 because your measuring cylinder is of 50. Right? So you will say that it is not possible since the capacity of the measuring cylinder is 50 cm. Ok? good OK. Let me just see.

[00:27:37]No. Well, it is 30 in every case, isn't it?

[00:27:40]So this is saying well what was V? Let me take a look at it once.

[00:27:48]70cm * The can may not have that much capacity. Right?

[00:27:56]To measure a volume V of 70cm and say Places a finger under the hole at the bottom of the can Pours the water Removes the finger Starts the stop watch A records a time T1 When the volume collected is 0 in the measuring cylinder By 30 This is stopping right. So it is possible that if he reduces the volume further then it may take a lot of time for him to reach 30. Right? And it is possible that if it is touching the side of the can then it may not reach the full 30 cm. Right? There may be a little sticking to the funnel as well. It is possible that 30 may not be completed. So, this could be a possible reason.

[00:28:36]So, in these suggested parts, you have to look back a little further into the procedure.

[00:28:40]So, you said Why Isn't Measure Below 50? So you said that brother less than 50 the smaller measuring cylinder may not fill up to 30 since some reduction may be on can or hands or funnel.

[00:29:20]Correct? So if some water gets stuck here then it is possible that it may not fill properly up to 30 cm. On your graph, sketch the line you would expect to see. If the small hole in the can is made slightly bigger, label this line L. Well, when it is said in physics or chemistry or biology, the meaning of line can also be a curve. Like you have created the curve. So obviously now this one that you will make will also be curved. So what if the hole is bigger? So if the hole is bigger then it will take less time. Right?

[00:29:52]Yes, I also told you it was below Rs 50, Ryan.

[00:29:55]If it is below 50 then it means that the volume you have here, son, is not 50, it means it is less. Now it is so full. Suppose I put it here.

[00:30:08]Son, in this experimental procedure it is written that it will be completely filled by 30. So I'm saying if he takes less volume let him take 40. So maybe the 10 cm that is there may either fall a little bit during the transfer or stick to the can or stick to the funnel or stick to it when the child places his finger on it.

[00:30:24]Right? So all of these are a few ideas. Did you understand? Good. So basically if you have this then the time will be basically less.

[00:30:36]Right? So a bigger hole means less time. So, I mean, I make my line something like this.

[00:30:50]Right? I am just running out of time.

[00:30:54]If earlier some time was being taken for each value of V, now it is taking less time here.

[00:30:59]So that's how we have drawn this.

[00:31:03]Ok?

[00:31:12]Ok. Okay, and let's see its marks theme.

[00:31:16]Question three of Sum 25 Paper 41.

[00:31:33]Good sir. So what are the marks for here?

[00:31:37]This is what he told you, and this is what you'll always see in a good graph of his calculations: the axes labeled quantity and unit scales are linear, not arc, and should not start from zero.

[00:31:56]So son, one thing was that if he said not to start from zero, then you should just not start from zero. Points plotted accurately thin best fit curve line drawn. Okay now look what it says in this might take too long not enough water in the can. So basically we said that if there is not much water then it means it should not fill up to 30 cm. And the same thing is that the way the can is kept, it is possible that some water may remain on the sides of the can and it may not be completely filled. Right? A curved line below the plotted line for the entire range and labeled L. So this second purple line that we made is its graph.

[00:32:35]Ok?

[00:32:37]A I would really say a steeper gradient basically for every value of V now the time is less.

[00:32:47]Ok? So this was a question related to general physics. Now let us look at some more questions.

[00:32:53]Well, this is October, November. So let us see some more questions from May to June.

[00:33:04]So which one was it? 41 Let's try to do something from 42.

[00:33:11]Yesterday we talked about such a question. We did this yesterday.

[00:33:16]Hum Hum Okay let's try out.

[00:33:19]Something like this.

[00:33:23]This is another graph question and this is related to springs. In general physics itself it is related to spring. So now let us try to look at this question.

[00:33:34]So just a minute.

[00:33:57]Okay this is question number three. So graph questions are almost always question number three by the way. A. So first of all there is either scale measurement or something like this. Then whatever happens to you is what they say.

[00:34:16]One minute what a BD scale I've never actually heard of it.

[00:34:49]But I wouldn't suggest whatever that is.

[00:34:52]See, you mean back to back, if you are thinking that much about the curve then you are obsessive over it and you don't have to obsess over it, you just make a smooth in it, then that is not that important, other things are more important, frequently tested ideas for P4 safety, so see, it is never asked in your P4, right, but the other things are included in the notes, I have not made a separate video on that, okay, now let's see this. So This Is Some 25 Paper 42 Student Investigates the Stretching of a Spring. Student suspends the spring from the clamp of a [ __ ] stand as shown in Figure 3.1.

[00:35:35]The student takes readings from the meter rule to determine the length of the spring. On 3.2 take readings from the meter rule ah with the top of the string and level with the from the meter rule level with the top of the string and level with the bottom of the string do not include the loops at the top and in the bottom of the string in your measurements record the readings to the nearest point one C means that's saying take the reading from here to here. So when you have the scale, make a line with the pencil in this manner. Just go away from here.

[00:36:10]You should just go away from here. So this is going from 39 to what seems like 41.1. So the reading level with the top is 39, but you would write it as 39.0.

[00:36:23]Why? Because you know that your meter rule could take the smallest reading even in 1 cm. It is a coincidence here that it exactly aligned with 39.

[00:36:33]Then write 39.0.

[00:36:37]Write the second one as 41.1. I have also told you this that whenever you take a reading from an instrument you take care of decimal places and whenever you use calculations then you take care of SF significant figures. Draw on 3.2 to show how the student uses the set square to take a reading from the meter rule level with the bottom of the string. So this is saying how do you use the set square brother? So what is the function of the set square? Well, it is saying to make it at 3.2.

[00:37:08]So brother, the work of set square is that set square is basically going to ensure that it is perpendicular.

[00:37:19]Right? So you just got yourself insured that your meter rule is perpendicular and in this way you took its reading. I basically wanted to ask this 3 one pe but this is what it is okay so here you should make it so it should be drawn on the other side from the okay the usage of set square here is a little different. Right? What it's basically trying to do with this set square is just letting you take a reading from the meter rule level with the bottom of the string.

[00:38:40]So how to see from the bottom? Well, the job of a set square is to show what it is basically like to insure perpendicularity. Right? But here it will be used for this thing that brother you kept it like this and then you just complete it like this.

[00:38:59]To show that friend, I have taken the reading from here.

[00:39:02]So this is its function here. Right? Ok. So that's this.

[00:39:06]Next calculate the length l of the coiled part of the string.

[00:39:24]Use the equation below. So L is reading level along the bottom minus reading level along the top. Show Your Waking is one of Mark. Still show your waking. You have to show this. So 41.1 - 39.0 which is 2.1 okay? Record L in Table 3.1 on page 12 for a load L of 0 newtons. Ok? So this 2.1 comes here.

[00:39:55]Well, what does he say next? Further, the student places a load l = 1 Newton on the spring and takes readings to determine the new length l of the string. The top of the spring does not move, but the bottom of the spring moves downwards. So he is saying that the top remains at the same level. The bottom came down. Student Determines at the new reading on the rule level with the bottom of the string is 45.2 Calculate the new length L of the string. So 45.2 A is the one below. The upper level is saying that it is still at 39.0.

[00:40:26]So 45.2 - 39.0 which is 3 not 3.2 ah this is 6.2 CM so here you have 6.2 okay. Good sir.

[00:40:45]On the grid provided in 3.3 on page 13 plot graph of l on the y axis against l on the x axis. Well, the small l is on the y axis, the big l which is the load is on the x-axis, draw the straight line of basefit, use the data in 3.1, and this is this. But first let us make a graph. Ok?

[00:41:04]Ok? Look there, whether it is drawing a line, a curve, IGCSE or O Levels, you always get six marks in line drawing.

[00:41:12]Sorry it costs four marks.

[00:41:14]So you labeled your grid first.

[00:41:18]A sorry axis labeled it. So l sum on the y axis.

[00:41:25]So here comes your lcm.

[00:41:29]Well, I like to do it here, but you may also do it here.

[00:41:33]That's what some people like, and again, it also makes sense because you have a barcode on the paper up here, so you can do this too. Ok? And below is your l Newton.

[00:41:49]So you have to write here if you can write here also.

[00:41:52]I have a habit of writing in the corner like this but it's totally up to you.

[00:41:59]Ok?

[00:42:02]Also take care not to write on your barcodes for the practical purpose of your exam. Suppose I wrote L CM like this.

[00:42:13]No, this cannot be written. But this should be visible from your reading, son. Okay, now let us select the scale. Again a load l is on the x-axis. So that's really easy. He said start from zero.

[00:42:26]So it made things easier for us.

[00:42:28]Where he himself gives us the option that you should not start from zero. If you have noticed, we have to think more about it.

[00:42:35]Right? From which value should we start and how far should we go? So how many boxes is that? So basically you have it easier in this case. So starting from zero. On the x axis you have to go up to five. Right? So see if you did one here, two here, three here, four here.

[00:43:01]Now in this way five came here.

[00:43:04]Again this is good enough. Because you are using more than half of the grid. So this is good enough. It's your wish. If you want to complete the rest, then do it. There is no harm even if you don't do it.

[00:43:18]Ok? Yes, this is also FGC P6.

[00:43:21]And then your length is going to be 21.9 let's keep 22 in mind. So let's just first play around and see how far we can go. We have to go till 22nd. If I do 2 4 6 8 10 12 14 16 18 20 and 22. So this is perfect.

[00:43:45]Let's start with this.

[00:43:47]Well, it would be better if you write one here, 1.0.

[00:43:59]But again it doesn't really make a difference. And secondly, you have to go from there to here to there.

[00:44:07]Yes. Yes, but son, now like this is the case, I mean, now the problem with that formula is that sometimes it gives you and this is what the examiner means by awkward scales, sometimes it may be that your value is coming out to be like this small box value, right, its value may be coming out to be 62, which is a weird scale, and the examiner will deduct your marks.

[00:44:32]So it is best that you check it yourself to see how much is the value of one box.

[00:44:37]So it should look like it should look normal.

[00:44:41]So look at this this is your 2.0 then 4.0 then 6.0 8.0 10.0 then 12.0 14.0 right? So this is how you completed this labeling.

[00:45:30]Then you have to select these points.

[00:45:32]So the value of zero pay load length is 2.1 so 2.1 ah so this is three so 0 pay 2.1 that's here right then a one pay 6.2 6 2 then two pay 10 three pay 14 so two two pay 10 three pay 14 all right then four pay 18.2 five pay 21.1 four pay 18.2 so this is 4 18 2 and then 5 pay 21.9 so five pay 21.9 which is probably going to be here like this.

[00:46:44]Ok? All the points were visible.

[00:46:47]You have to create a line of base fit.

[00:46:49]I have also told you the method of Line of Basefit.

[00:46:51]I talked about this a lot in the last class.

[00:46:55]So let's say this is my scale. Let me draw a scale right now.

[00:47:03]Ok? So you caught the scale. Turned the scale.

[00:47:10]And you saw that in which case I have like the best split of points. Like I'm pretty lucky because this is really nice. Well, this is not really my point. I will remove this. it is.

[00:47:26]So, now watch it with Something Like This.

[00:47:34]This is pretty nice. Right? Because as per my observation, the recovery is a few points below here and this point is above by the same amount. As low as this is, this is also as low. This is a little bit higher. So, this is like fine. Right?

[00:47:46]So, now you just need to make your line like this.

[00:47:59]Again this is something again easier to do on paper than on the graph. So this is how your line was formed. Ok? Well, one more thing to note is that when we use gradients etc. then we select points on the line rather than the points you used for plotting. Because it is possible that when you have drawn the line, your line may be the point according to which you have drawn that line, may be the line is not necessarily passing through that point, so you will use points on the line. Ok? Okay, now this is saying use the data in 3.1 and the graph in 3.3 to determine the extension because this is giving the length of the string when a load of 3.5 Newtons is added to show your working. So I will first see at 3.5 what the length is. So 3.5 This is not very difficult to see. Here's a 3.5 something like this is a 3.5 so for me it's actually leveling up beautifully with the 16 mark.

[00:49:12]Right? So this is the length. Right? So the length is 16 cm.

[00:49:19]So my length became 16cm.

[00:49:25]But he has asked for an extension. So I also know the old length, when the load is zero then it is 2.1, so what is the extension? New length minus old length which is 13.1 ok?

[00:49:45]A student suggests that the strength L of the string of the spring is proportional to the load. State if the data in 3.1 supports this suggestion. Justify your statement using the data in 3.1 and the graph in 3.3. Well, those who have studied this theory carefully know that the answer is no, it is not proportional. Because in every case where one thing increases and the other thing also increases that is not directly proportional. Ok?

[00:50:12]Those who are good at maths might also say that sir this is not a direct proportion because the graph is not going through zero zero and that is also fine. But the Examiner wants you to justify using the data. Correct? So you pick any two data points. Right? Suppose I say one to two and let's say one to four. Right? We know that direct proportion means if one thing is doubled then the other thing should also be doubled. So here if I'm going from one to two, it should be 6.2 to 12.4. This is going to be 10.

[00:50:52]Let someone from the front say that this happened because of your experiment. Ok?

[00:50:56]So if I'm going from one to four. If my load is times four then my length should also be times four. If it was directly proportional, but it is not happening.

[00:51:06]So this is not directly proportional. So, you should talk according to two values. Just in case the examiner says that you spoke according to one person only. Who knows, that might have been a wrong reading.

[00:51:15]So let's talk at least two.

[00:51:19]So the first thing I know is that the statement is wrong and not proportional.

[00:51:28]Ok?

[00:51:30]Then you said when load lets say triples from one to 3 Newton the length does not ripple let's say in the same way that if we talk about tripling from one to three so ah should have been 6.2 times 3 which is 18.6 and in the same way you can talk about one more point also.

[00:53:26]Ok? Well, it has said that order the graph, so you could have also done the graph thing that if the graph is of direct proportion then it should go through the origin but we have done it according to this, it is just better to use the data line of side errors can occur when readings are taken from the meter rule state one practical technique other than using a set square that insures accurate readings are taken from the meter rule, well what else can we do, apart from a set square what can we use, so ah we can just say this that I level should be perpendicular to mark being red.

[00:54:29]Ok? The student repeats the procedure described and seen two more times and averages the readings before calculating the swing lens l for each load l Explain why the student does this. So he is saying that why does he give multiple readings and then average them? So we say that this reduces uncertainty and this is its technical term. So you guys keep this in mind. This reduces the uncertainty or instead of uncertainty you can say the effect of random errors. Well, what do we mean by random errors? It is that basically, the problems that arise due to slight fluctuations that occur to you are called random errors. Apart from this, you can also improve the precision of the readings. Correct? Ca n't say it improves the accuracy. Improves the Persion says that whatever is happening due to it, it gets better. So that's the idea here.

[00:55:44]Ok? So this was another question that also involved drawing and this was yours as well. What do you say? There were also questions from General Physics.

[00:55:55]And go back. We just did this.

[00:56:21]Well, either scale diagram comes in general physics or you get graph.

[00:56:28]Ok? Let us also ask such a question.

[00:56:36]Its start is gone. Here it is. So these are moments. So in this you will get a lot of these questions in 2023 O Levels and in 2024.

[00:56:49]Well, fixed mass is placed on the measured rule at the 5 CM mass is shown in 3.1 minutes, give me.

[00:57:55]So, a fixed mass is placed on the meter rule at the 5 cm mark is shown in 3.1. The student places the pivot below the 25 cm mark on the meter rule. Places a mass of m20 20 g on the metered rule. Adjust the position of the 20 gr. Mass until the rule is as close to balance as possible. Correct? Now when you are asking questions, I have told you to pay attention to the procedure yourself, then you will understand many things.

[00:58:20]I had also told you this thing through the notes that what we say about balance being achieved, happens only in theory. In reality, it only gets as close as possible to the balance. Position of the 20 gr. Mass, Ah When the Rule Is as Close to Balance as Possible is Shown in 3.2. Using 3 2 determine the distance d of the center of the 20 g mass from the pivot when the meter rule is as close to the balance as possible. So what happens is that if you are not able to see the center then you can look at the sides and by averaging the sides you will know what the reading is. So look at this side it's leveling up with the 81.1 mark and this side it's leveling up with the 82.9 mark. So this side of yours has become 81.1. This one became 829. So what will be its centre? So center I said 81.1 + 82.9 / 2 but keep in mind this is not my final answer. He is asking me the distance from the pivot.

[00:59:33]So 82.9 / 2 is 82.0 so the center is at 82. Well, where is Pivet, brother? The pivot is at the 25 cm mark.

[00:59:44]Right, so we're going from 25 to 82, so it's 82 - 25, which is 77.57.

[01:00:04]Well, describe the technique that the student uses to balance the meter rule with the 20 gram mass. We have already discussed how you answer this. So you said adjust the position of the mass as the rule just starts to tilt one way.

[01:00:44]And then I adjust so it just starts to treat the other way okay.

[01:01:06]Okay, let's do the remaining parts.

[01:01:11]Student repeats the procedure for the values ​​of mass of 30 for D 50 60 3.1 shows the results. Add your value of D for mass 20 grams in A1 to 3.1 correct? So we add the value that was coming to us.

[01:01:25]Okay, 1 minute.

[01:02:01]Okay, our value of d was 57. Now let us see, it should also look correct according to the rest of the table, which is what it looks like here. And then it's saying calculate the value of 1 over d. Give your answers to an appropriate number of SFs. So what does appropriate mean here, that this is 2sf, you are taking the reciprocal of everything. So your answer should also not be your 1sf sorry 1sf. Must be 2sf or 3sf.

[01:02:34]So 1 57 This is 7 0175 So I'm writing this down 018 I tell the kids this in AS as well. I will tell you guys the same thing right now that the lesser number of SF that you use, it's actually going to be better. And the reason is that brother, when you use less number of SF, your plotting will become a little easier. It will still be the same. Then 1 37 then 27 then 1 then 0357 then 36 then 1 22 then 454 then 1055 then 56 Suggest why a value of d cannot be found for the mass m = 10 grams. So he is saying why can't the value of d be 10 grams? So think for yourself what is the value of d right now? 57 right? Where was 57? When he himself was 82. So maybe if we reduced the mass further. Right?

[01:03:54]If the mass is reduced further, then you know it will have to be taken further away. So it might go beyond the meter rule. Right?

[01:04:01]So we can say that the ruler is not long enough. Right? Very easily. So de wood be grated and the rule may not be long enough.

[01:04:31]Ok?

[01:04:33]Using the grid provided in 3.3 on page 13, plot one over d on the y-axis against m on the x-axis. Well, see, he himself has given the units etc. here.

[01:04:42]By the way this is how you write the units. Ah start your axis from the origin zero zero draw the straight line of breast fit. Ok? Good sir. So let's write 1 over d on the y axis.

[01:04:57]So 1 d 1 over cm okay? And what is on the x axis?

[01:05:06]m Right so m g well starting from zero zero.

[01:05:19]Ok?

[01:05:20]And going from 0 to 60 over here. So this is easy. The second one just needs a little look.

[01:05:26]Right? So this could possibly go from 0.01 up to 06.

[01:05:35]Okay? Let's look at this. So let's talk about mass.

[01:05:40]So if you want to go 10, 20, 30, 40, 50 and 60 then go a little further also.

[01:05:56]70 and 80 okay? Okay, go from 0.01 to 0.06 if I do this and again this is just experimentation right now.

[01:06:11]And then it becomes 0.02, three, four, five and six. If it's six, you're seeing I'm actually using way to less off the grid. So I'm using half the grid. So I double my scale.

[01:06:26]So instead of putting 0.01 here, let's say I put it here.

[01:06:33]Right? This is my 0.0100.

[01:06:37]Then my four boxes arrived. Again this is my 0 02. Then four more boxes arrived. This is my 0.030.

[01:06:50]Then four more boxes arrived.

[01:07:01]Okay, like this, four boxes have arrived, I am not able to take all of them. Will I still get my reading?

[01:07:10]Okay I have to now look at this. So I have to do 56, let's see. So55 will come till here. I Am Pretty Show 56 will also be coming. When we plot, we see whether it fits or not. So 60 on 56 so 60 on 56 so this is 55 right. So this 5 6 that we have to look at I actually hit this type of scale. Meaning there is no issue anyway. But the plotting becomes a little difficult in this. I mean, these weird things happen in it like this is 51 52 5 4 53 54 right? So 56 will come here. Ok? Infact it's not all that bad.

[01:08:06]So yes, where it goes to another decimal place, I mean, it seems like a lot to white with 60 right here, right? 60 is here, 60 was right? Yes, so 60, this is 60, so let me bring it here, this is 56, right? So, yes, it fits perfectly.

[01:08:36]Now, let me get rid of this.

[01:08:42]Then 50 pe 045045 will be between these two. Here it is.

[01:08:55]Then 40 p036 0.035 here it is. 0.036 Here it is.

[01:09:11]Ok? Good sir. Then 0.027 at 30 becomes 25. This makes it 26. This makes it 27.

[01:09:28]Ok? And then 20 pe so 15 167 18 came here. Correct then 19 and 20 are done in this manner. Again, if you want to create your line of base fit, then take a scale.

[01:10:00]Correct. A transparent scale is required for this. I have told you guys before.

[01:10:05]You keep the scale and see what looks nice.

[01:10:11]Possibly there may be a slight tilt.

[01:10:14]Something like this.

[01:10:21]Missing the point above. He's making matters a little worse.

[01:10:26]So we will try to leave as many points below as we left above. There are two left below.

[01:10:34]Missing one above. So let's do it a little like this.

[01:10:38]So now this is good enough. Right?

[01:10:42]I hope you guys can see this. See this, this and this. Right? Also, it is not even necessary for the line of base fit to pass through a single point that you have plotted as long as it goes as close as possible to the points that you have plotted. Close as Possible is the key here not actually passing through the point. Ok?

[01:11:11]So, this is my graph drawn.

[01:11:16]All right.

[01:11:18]Now I have to make it, let's see what to do next.

[01:11:25]That's saying draw the straight line of best fit don calculate the gradient g of your line. Show all your working and indicate on the graph the values ​​that you use. So this is what I have told you guys that we choose ah points very far apart. So, if one is seen somewhere above, the other one should be somewhere below. Let's start looking from the bottom.

[01:11:43]This is possibly one point.

[01:11:47]Right?

[01:11:49]Here's a point. So if this would have been five, this is two. So this point is 2 0 right? And then let's see the second point somewhere above.

[01:12:09]So possibly something like this.

[01:12:13]Ok? It's lying at the exact edge of a box. The y coordinate is 51 and what is the x coordinate? Between 50 and 60.

[01:12:28]So this is 55.

[01:12:31]Ok? It is not necessary to do this here.

[01:12:34]But I like it. I do this in s. I do this in A2 as well. But like is not mandatory. It is natural here that you make your triangle and show it.

[01:12:44]You will have to use these values ​​in future anyway.

[01:12:47]This is your vertical line. This is how your horizontal line came. Ok? Then you calculated the gradient.

[01:12:57]So y a pe051 - 0 so 51 - 0 y2 - y1 did I over x2 - x1 is 55 - 2 okay? Let's do this. How much does it come to? 051 53 Basically it is 9.62 * 10 to the negative 4, okay? This is my gradient value coming out.

[01:13:35]Ok? So again mark scheme says that brother 9.6 + -1 means it is saying that 9 is also accepting 10.6. 8.6 is also accepting. You can see for yourself that lines like mine are made very well. So it's actually very very close to the point that he specified. Ok? Good values indicated a greater than half the line used.

[01:13:59]We have done this thing.

[01:14:02]And then it says that the mass m of the meter rule is given using this equation use your value of g in b2 to calculate m is correct so there is no issue. So m is 160 -040 over whatever is stored in my ans variable. It is better to tell this in writing also. So 160 -0 160 -04 04 by this thing so this comes to me 118.4 so I am writing it as 118 in 3sf you can also write 120. So the student is given a piece of modeling clay, he places it on the meter rule as shown in 3.4, he finds the meter rule, he finds that the meter rule is balanced when the modeling clay is at a distance of 40cm from the pivot. Meaning, he is saying that this gap should be 40 CMs.

[01:14:59]Which you know is basically d. Right?

[01:15:02]Use your graph in 3.3 on page 13. Find the Use your graph in 3.3 to find the mass of the piece of modeling clay show your working. So brother your d value is 40. Right? You made a graph of 1 d. So you see the value according to 1 over d. So how much is 1 40?

[01:15:25]1 d vi is 1 40 I think this is 0.025 so now you go to 0.025 and you see the mass so you will get the mass. So 0.025 is here.

[01:15:44]And you went here and you just watched the Mass from here.

[01:15:51]This turns out to be exactly 28 grams from me. So from graph this is 28 grams. Son, this was a requirement of the old syllabus.

[01:16:05]And I still do it. At some places in the old syllabus you will see that there is a mark for the use of triangle.

[01:16:12]Specially in AS. So I make it for this reason so that it can be seen that friend, this point has been selected. How far are you? So again the exact mass is coming to 28 grams. So, whatever line we made was very good. So he is saying that 28 + - 3 is the marks. So ya alright. Good. So this is what I had in mind. We have seen some questions about this.

[01:16:39]Now if you guys have any questions in your mind then please ask.

[01:16:53]This is what I had to do for today.

[01:17:30]All right. If you guys have no questions.

[01:17:32]So let's pause here.

[01:17:39]Yes, preparation will be done through physical workshop. So let's pause here and then Inshallah a this was the last session and then we meet again Inshallah physical workshop. All right. Okay, take care Allah Hafiz.