CSEC Physics - May 2026 Paper 1 Prep (Terry David)

追加: 2026-06-02

[00:00:05]Hey guys. Uh, good night everybody. Just let me know if you guys can hear me before we start, please.

[00:00:53]All right. So, um, this paper that I'm going to go through with you guys here, this is May 2025. All right. Um, I actually didn't have this paper at all. All right. One of my students just sent it to me. So, Let's have a look at it. Right. Let's have a look at. So this first question here, given that force is equal to mass by acceleration, then the unit of force can be written as what?

[00:01:18]Okay, so you all can just put your answer in the chat. Whatever you think is the answer, right? Just put what you think here. Right.

[00:01:46]Right. I've seen some answers coming through here. Most people saying the answer is C. So, first of all, we know that they actually told us here, right?

[00:01:53]Force is equal to mass by acceleration and they want to know the unit of force.

[00:01:58]So first of all the unit of force is in Newton. All right. And we are taking mass which is kg and you're multiplying that by acceleration which is m/s squared. So therefore what we're trying to say here is that the newton is actually kg ms to the minus2. Right? Right, that's the SI unit here. So, um, which one is that by kg?

[00:02:28]Sorry about the paper. This is just the quality of the paper that I that that was given to me. Right. So, C looks like the correct answer here.

[00:02:36]Uh, question two, which of the following is a vector quantity? So, look at this one here.

[00:02:44]An example of a vector quantity is what?

[00:02:55]Yeah, kind of blurry, but that that's the paper that I have, right?

[00:03:15]All right. So, we just had to work with it. So an example of a vector quantity, right? So just remember for a vector quantity, a vector quantity has both magnitude and direction. So based on what we have here, electrical resistance, nope, that's not a vector quantity. Heat capacity, nope. Density, nope. Displacement, definitely. All right. We normally use an arrow to represent displacement because it's a vector quantity. Okay. Um, let's look at this one here.

[00:03:44]Like I told you guys after a while, like I've seen all these questions before, which of the following instruments is suitable for measuring the diameter of a human hair, right? Which of the following?

[00:04:07]Yeah, like I said, sorry about the quality of the paper, right? This is this is the first time I'm seeing the paper. I have not seen the May 2025 paper one, right? So I literally somebody just gave me it so I said I'll do it.

[00:04:21]All right. So I seeing some D's coming through here. So yeah. So we want to measure the diameter of a human here. So the instrument that we're going to use is going to be a micrometer screw gauge.

[00:04:30]All right. Uh question four.

[00:04:36]What do we have here?

[00:04:38]Errors due to parallax can be minimized by doing what? So we're talking about parallax errors here. What do we do when we want to minimize parallax errors?

[00:05:10]All right. I seen some bees coming through. So first of all, let's talk about a par parallaxis, right? So let's say we have a measuring cylinder and you wanted to measure let's say a liquid, right? First of all, you measure or you put your eye at the level, right? You have to put your eyes here, right? So you're at the bottom of the miniscus.

[00:05:34]But look at something here. The actual scale on this thing here, right? The actual scale on this measuring cylinder is going to be on the side here. Right?

[00:05:42]But look at where you are viewing this thing here. You're actually viewing the scale at right angles. So in this case here, we are going to place our eyes at right angles to the mark being red.

[00:05:53]Okay? So that's why the answer is B for this one here.

[00:05:57]Question five.

[00:06:05]What about this one here? Power. How is power defined?

[00:06:15]How do we define power?

[00:06:30]Some people asking about the physic paper one. I almost certain all 60 questions that come in tomorrow would would be repeats, right? I'm almost certain about it.

[00:06:45]Right. So power is defined as work done over time, right? Or it's energy over time. That's power. So which one gives us that? Um work done over time. So the answer is going to be B. Yep. The answer is B.

[00:07:02]Right.

[00:07:09]Question six.

[00:07:12]Right. A block is allowed to fall freely towards the ground. As it falls, its gravitational potential energy does what? Question six.

[00:07:46]Right. I've seen some some D's, some people saying A. Okay. So, first of all, you have a block, right?

[00:07:55]It's allowed to fall freely towards the ground, right? So, let's say there's a ground here.

[00:08:01]Now, first of all, the block is going to have potential energy because it's above the ground. So, it's mg. As it falls, what's going to happen is that that potential energy, gravitational potential energy is going to be converted into kinetic energy. So, as the object falls, its velocity increases. So, in this case, there's a conversion from potential energy to kinetic energy. So what's going to happen is that the potential energy right is going to be converted into kinetic energy right so the answer is going to be D in this case here read your questions carefully right uh question seven looks like they just change a question a little bit there's a question that has a ring on it so they probably just alter this question slightly but it's the same So we have uh three forces of magnitude L, M and N applied all in the same plane applied to a ring. Oh, it's the same question, right? The same question. So they all apply to this ring here. And which of the following equations must be true in order for the ring to remain stationary? Right? In order for the ring to remain stationary, right? What is the answer for this one?

[00:09:48]Right? I've seen a set of B's here. So, first of all, what I would do in a question like this here, let's start with the two forces here that are at right angles to each other. So, what we could do, right, what we could do, we can complete a parallelogram here, right? And right, if I complete that parallelogram here, I can work out what this resultant force here is going to be. So the resultant force for L and M. So let's call that um let's call it R if you want. Okay.

[00:10:22]So first of all R 2 right is equal to L^2 + M 2. Those two forces are the right angle. So I can use Pythagoras theorem to work out the resultant force here. So therefore R is equal to the square root of L 2 + M 2. Right? So that's r. Now that resultant force here is actually going to be equal to n. So we can say that n that downward force is equal to l 2 + m 2 square root. If you look at the answers here, we don't have any answer looking like that. But if you square both sides of the equation, you will get n^2 is equal to l 2 + m^2. So that is going to give us b as the answer. Right? That's going to give us B as the answer, right?

[00:11:21]Oh yeah, some of you all remember, right? So, so those of you who are in my class, my actual physics class, normally when I tell students to write their answer in the chat, they put Q. So, like in this case here, they would have put Q7, right? Yeah, I see somebody remember that, right? So, it'll be Q7 and then we say um B is the answer, right? So it'll be easy for us to identify which question you're referring to. Right? But the answer is B.

[00:11:47]Right? So that's number seven. Let's see what number eight is about. Number eight here is about the moment of a force.

[00:11:58]Right? For those of you bouncing late, yes, it's not a good quality paper, but it's the May 2025 paper. I haven't seen anybody with this papers yet. So um the moment of a force is defined as what?

[00:12:10]Question eight.

[00:12:18]Somebody actually asking when is paper two.

[00:12:23]Paper two gone long time. Reds.

[00:12:40]All right. So, um, a lot of people saying the answer is D. Right. D. Let's see what's happening here. All right. So we speaking about moment of a force. Now just be careful here. CXE likes to bring questions that have moments and they have momentum right after because I know students confuse the two. So if I have a force here, right? Have a force here acting this way.

[00:13:06]This is a force F here, right? This is a pivot here. And this force is at right angles or the line of action is at right angles to this arm here. Right? Okay, let's say this is O A. So the moment of the force F here is given by F * D. That is what what is meant by the moment of a force. So it's the force by the um perpendicular distance from the pivot.

[00:13:31]Okay. So the product of force here has to be D, right? So D is the correct answer here, right?

[00:13:48]All right. So, that's number eight. Um, let's see what we have here. Number nine.

[00:14:02]All right. Which of the following measures can be classified as scalar quantities? What's the answer for number nine here?

[00:14:17]But some people even teach a class to come here.

[00:14:41]Right everybody's saying a so we're talking about scalar quantity here so a scalar quantity has magnitude only so time yes time is a scalar quantity speed is also a scalar quantity displacement nope not a scalar quantity so it's one and two so the answer is going to be a in this case here right um I just want to check something Yeah, the first question asks about or the second question. Oh, vector quantity.

[00:15:08]Okay.

[00:15:11]All right. So, that's number nine.

[00:15:15]This is number 10.

[00:15:33]Right.

[00:15:34]A body initially moving at a constant speed is brought to rest at a uniform rate. Which of the following speed time graphs indicates the motion of the body?

[00:15:45]Right. You don't find this looking like a maths question.

[00:15:50]Did you all find the CC maths was they had a lot of physics questions in the paper one.

[00:16:01]Glad to hear Nikisha. All right.

[00:16:29]All right. people saying uh C is the answer right so first of all they said that an object is moving at constant speed and it's brought to rest so if it's traveling at constant speed if I had to draw this if I didn't have the graph and I wanted to draw my speed time graph it's going to be traveling at constant speed this is what constant speed looks like it doesn't change and then it said it is brought to rest at a uniform rate it means that the velocity is going to come to zero right in period of time here. So this is what the graph is supposed to look like. So the only one that makes sense here is going to be C, right? C is the only one that makes sense, right? This particular one, I feel like every year they bring this question, right? Um this question here could have come in your paper two for six marks.

[00:17:24]Okay, we have a um a 4 kilogram mass.

[00:17:28]It's traveling at a constant speed of 5 m/s. It is brought to rest in 2 seconds.

[00:17:33]The average force acting on the mass to bring it to rest. So this is so weird, right? Because exactly the question before is exactly the same speed time graph as what they asking me here in question 11. All right.

[00:17:54]Yeah, that that that that I agree that that that math paper was was a little unfair to you guys. There was a lot of working. I took a while to work the to work the paper. All right. Um there were lots of calculations to finish in that hour and 15 minutes or so. That's that's a lot of calculations to do, right? What about 11 here?

[00:18:24]Let me let me just uh give you all a piece of advice, right? I know some of you all may have learned of answers, but still read the question, right? Still read the question before putting on your answer, right? Um so for this one here, let's let's look at what's happening here. So first of all, they're telling us, right, that you have a 4 kilogram mass. So first of all the mass is 4 kg.

[00:18:47]All right and it's traveling at constant speed of 5 meters/s. So this is what's happening here. You have a constant speed of five. So this here is speed in meters/s and this is time. So it's traveling at this constant speed of 5 m/s. Okay. Then what happens is that it's brought to rest in 2 seconds. So what's happening here now is that its speed is going to go down to zero. But this time interval here right is going to be 2 seconds. So this time interval here is 2 seconds. So first of all your initial speed is five and your final um speed is zero. So therefore you can work out the acceleration. So the acceleration is v minus u all over t. So your final velocity is zero minus your initial which is 5 divided by your time which is 2 seconds. So this is - 5 / 2.

[00:19:38]Right? And this here is m/s squared. Right? So that's the acceleration. You want to figure out the force that is bringing this object to rest here. So we're going to use Newton's second law. F= ma. So the mass in this case is 4 kg * a your acceleration which is - 5 / 2. So 2 into 4 is 2. 5x2 is 10. So we get - 10 newtons. The reason why we have a negative sign here is because this force is opposing the motion of the object in order to bring it to rest. All right? So the answer is C in this case here, which is what everybody's saying anyway. Okay.

[00:20:34]right? So that's number 11.

[00:20:39]Number 12, right? A piece of string is tied to a small stone and then the stone is totally immersed in water. The tension in the string will be what? Okay, so question 12.

[00:21:02]Right. By the way, if you haven't done so, please remember to hit like and subscribe, okay?

[00:21:20]only formula where um at least with this question here is we need F= ma and we need um the acceleration formula but for for the paper one you don't you don't need to remember that many formulas for the paper one All right. So, let's see what you all saying for this one here. You all saying B. Let's check that. Okay. So, a piece of string is tied to a small stone. So, first of all, um let's say we have the string here and it's attached to a small stone. All right. What's going to happening happen here is this.

[00:22:15]The forces acting on this here will be weight acting downwards and then we're going to have our tension acting on the string upwards here. Now in the second scenario now we taking that same stone now and we totally immersing this thing in water. Okay. So basically right we're taking that same thing here but this time what we doing we're placing it in water. Okay. So this is our scenario here.

[00:22:41]So again, look at all the forces that are acting on that stone here. So again, you have your weight acting downward.

[00:22:49]You still have the tension acting upwards as well. But there's a third force that comes into play. Now that third force here is what we refer to as your uptrust. So there is an upward force here that is pushing you upwards here and that's called the uprust. So the tension in the string all right in scenario one here we just have tension is equal to the weight but in scenario two here we have tension plus the up thrust must equal to the weight.

[00:23:21]So therefore the tension is going to be weight minus u. So what does that tell you? That tells you that the tension in the string is less than the weight in this case here. Right? So in this case here, we're going to say that the answer is going to be B, right? The answer is going to be B here. Less than the weight of the stove, right?

[00:23:46]So that's number 12, right? Number 13.

[00:24:09]where the string hang on to. You could you can use your hand. I just put that as a fixed point here, right? I just put that as a fixed point, right? So, you can actually um you could be holding the string, right? I just put the fixed point here because tension is normally directed towards a fixed point.

[00:24:35]Right. Um, yeah. What about this one here? Uh, question 13. What you all think about this one?

[00:24:44]Oh, I don't remember what I was going to say. So, sometimes, uh, CXC repeats certain questions from older papers. And what I realize sometimes is that they don't necessarily check to see if that topic is still on the syllabus. I've seen that happen before. Certain things that are not on the syllabus, we still get tested on it. Okay.

[00:25:11]All right. So for 13 people saying the answer is a. So first of all, here's what's happening here. So you want to the acceleration due to gravity is to be determined by measuring the time taken for a steel ball to fall through a specific height. So basically you have a steel ball here. Okay. And it falls through a specific height. So let's say we're measuring the time taken for the ball to go through this height here. And we need to measure the time, right? You need to measure the time. Now based on that information alone we have to be able to calculate what is the value for the acceleration due to gravity. Now first of all your initial velocity here will be zero right that's your initial velocity. You're going to have some final velocity here v right now one of the formulas that we actually using here is this s is equal to u t + a half a t².

[00:26:08]Okay. So the height is given by u t your initial velocity is zero. So it's u by so zero by by your time right whatever that time is plus a half by the acceleration the acceleration is g t ^2.

[00:26:25]So therefore h is equal to gt ^ 2 all over 2. If I rearrange this formula I'll get gt ^2 is equal to 2 h. So therefore uh g is equal to 2 h all over t ^2.

[00:26:42]Right? Now this is just one way of working this particular problem. I know some students may have done this as an SBA lab in school to determine what's the value of g. So now um what are we going to do here? So first of all to calculate g you need to measure h. So h is required and t is required. Now if you notice it said which is unnecessary according to my formula to calculate G.

[00:27:04]There's no mass inside it. So therefore I don't need to find the mass that's out right. I need the height. Yes I need this. I need to measure repeat the time measurements because you want to improve your accuracy. Um allow the ball to drop and starting the stopwatch at that same instant. Well that's how that's your technique you're going to use to measure this. Okay. So in this case in this experiment here only H and T are required right that's number 13.

[00:27:37]Question 14.

[00:27:40]What do we have here?

[00:27:43]On which of the following features does the pressure at a point in a liquid depend on if I play Roblox? Nope, I don't play Roblox.

[00:28:15]I have a very very very busy schedule every day.

[00:28:36]All right, I think you were saying eight. So first of all when we speak about if this is the surface of a liquid and you want the pressure at some point below the liquid here. So the pressure in a liquid right or in a fluid is given by row gh. So it is dependent if you read the question carefully the pressure at a point in a liquid is dependent on the density of course because density is in the formula. The depth from the surface that is what this h represents here. This h here represents your depth from the surface. So this is true. The area of the cross-section area of the cross-section has nothing to do with the pressure. Okay? Area is not even the formula. So it's one and two only. The answer is a right. Question 15.

[00:29:29]Let me tell you how far back they bring questions from. Right? This you see this question here. I got this question in my CC physics exam way back whenever.

[00:29:37]Right. Um, question 15. What do you all think about this? So, Yeah, that's how old that question is, right? That question real. Okay. Um, so let's see. Right. Um, we have a diagram here. It shows two containers P and Q. Each container different size has water blah blah blah right P and Q are connected um by a glass tube and the flow of water is controlled by this tap here when the tap is open so first of all because this is open here you have atmospheric pressure acting here you have atmospheric pressure acting here what's going to happen here is that the pressure on the surface of the liquid across here is going to be larger than across here so what's going to happen is going to push the water. So, it's going to pass through the glass tube until both levels are the same. That's what's going to happen here, right? So, water levels P and Q are the same, right? So, the answer is B, right? Um, yeah, some of you all asking about Admats. I'm not too sure about the Admats one, right?

[00:31:27]I think today might be my my last day of live streams for a little while.

[00:31:34]All right. This is also a repeat also a very old question as well.

[00:31:49]All right. So, uh we have um a diagram shows two vectors of magnitudes A and B.

[00:31:56]Uh the vectors point at the point O are directed perpendicular to each other.

[00:32:01]Which of the following pairs represents both the magnitude and the direction of the resultant? The answer for this one.

[00:32:40]with respect to ADMATS they tend to be bringing some some newer questions in the paper one though. Okay. And with respect to with respect to the the paper one, remember the syllabus that you guys are using for ADMATs is effective 2021.

[00:32:57]So the only papers that are in line with your syllabus is 2021 22 right up to 2025. That's it.

[00:33:09]All right. What's happening here with this one? What people saying? D.

[00:33:13]Question 16, right? Some people saying C. Okay. All right. Let's see. So, first of all, they gave us some information here. They said this is A and this is B, right? So, let's start with the magnitude here. So, first of all, both vectors are at right angles to each other. So, they've already completed the parallelogram for you guys. So when two vectors are perpendicular, the magnitude is going to be along this diagonal here.

[00:33:42]Right? So this here, let's call that the resultant vector. So first of all, the resultant vector will be in the direction OC. So that's the first thing we're going to look at. So this one says OC and this one says OC. So the answer is only A or D. Now, how do we get R here? You're going to use Pythagoras theorem because this is also A here.

[00:34:04]This will be a right angle. So we're going to use r 2 is equal to a^2 + b^2.

[00:34:10]So therefore r your resultant vector is going to be the square root of a square + b square. All right. So the answer is going to be this one here d is going to be the answer.

[00:34:32]Right? So, be careful with your answer for this one. See, some of you all didn't get correct.

[00:34:53]All right. Uh, question 17. So, so these are things that that I don't fully understand why CXE does, right? They literally just asks us a question about pressure and talking about how does liquid pressure depend or what does it depend on and then boom they give us a question in 17 here which is basically the same kind of question. What's the answer for 17 Right. Uh seen a lot of lot of A is coming through. So yeah. So literally the same question before like pressure is row GH. So it's dependent on the depth of the water. So the answer is A.

[00:35:45]Okay.

[00:36:01]What is the gain in gravitational potential energy of a body of weight? So the weight is 200 ntons.

[00:36:11]All right. It raises from a height 30 m.

[00:36:15]So we're going from 30 m to 35 m.

[00:36:21]And we want to find the gain in gravitational potential energy. What's the answer for that one?

[00:36:36]All right, I've seen some C's. So, first of all, your change in gravitational potential energy is equal to mg delta h.

[00:36:59]That's the formula we're going to use here. So, we didn't give us the mass here, but they give us the weight. So remember weight is equal to mg. So all we need to do is to substitute 200 multiply by the change in the height. If you're going from 30 to 35, the change in the height is five. So that's 5 at 10. So therefore this is a,000 jewels here, right? So the answer is going to be C.

[00:37:30]That's number 18. Question 19.

[00:37:35]Which of the following statements about pressure law is true or are true?

[00:37:57]Right.

[00:38:05]Somebody's asking how long I'm going live. Well, I'm doing all this this this May 2025 paper for you guys. Right.

[00:38:16]Right. People saying B here. So, first of all, we talking about the pressure law. Now, the pressure law basically looks like this. We can say that um so pressure is directly proportional to your absolute temperature right that's what the pressure law basically says. So you can write the pressure law as P is equal to K by T or you can write the pressure law as P1 over T1 is equal to P2 over T2. So those are different ways of writing the pressure law. So let's read this. Now the volume is constant.

[00:38:47]So if you notice in the formulas here there's no V. That tells us that volume is constant. So that is true. Pressure is constant. Nope. That can't be true because pressure is changing. You have a P1 and a P2. So the pressure is changing. The ratio of the pressure to Kelvin is a constant. Now you see this this equation here. If I rewrite this, I can say that P over T is equal to a constant. So this this statement here is true as well. So the answer is one and three, which is P, right?

[00:39:29]Right. So that's number 19.

[00:39:32]Question 20.

[00:39:38]What about this one here? Which of the following materials is both a good absorber and a good emitter of heat energy?

[00:40:04]Yes, Sura, I don't mind doing those kinds of things.

[00:40:11]All right, I've seen C coming through.

[00:40:12]So, they said, um, so good absorbers are also good emitters. Are we talking about black surfaces? If you look at the answers here, you're going to you're going to see they talk about polish.

[00:40:22]Polished, right? The only one that is not polished here is C. That's this one here. All right. A flat metal plate painted black. Black surfaces are good emitters and they are good absorbers of thermal energy.

[00:40:42]Um, question 21 here. I've seen students even in some of my classes get this question wrong here. And it has to do with how the question is worded. So the specific latent heat of vaporization of water is 2.26 by 10 6. When 0.1 kg of water is converted to steam, which one is the correct answer?

[00:41:41]right? So some people saying a so first of all right we speaking about latent heat of vaporization and we starting with water right so you're starting with water now you're is latent heat of v vaporization so you're converting the water into steam so first of all the water has to be at 100° C and this here is steam at 100°C now um we're going to use the formula E is equal to M by L V the mass of the water is 0.01 * LV which is 2.26 by 10 6. So when I work this out here that's going to be 01 by 2.26 by 10 6 and we're going to get uh 2.26 by 10 4 Jes. Okay. So first of all that could either be this one. So yes it is blurry right but these two here are by 10 to the 4. Now if we are converting from water into steam that water needs to absorb that amount of energy in order to be converted into steam. It's not going to give up that energy has to absorb that energy. So the answer is a right. The answer is a. Be careful with this.

[00:43:02]Right? You need energy in order to be in order to convert from a liquid into a vapor, right? So it has to absorb that energy. Okay.

[00:43:11]So that's 21.

[00:43:22]Question 22.

[00:43:24]Right.

[00:43:27]Right. For those of you bouncing late.

[00:43:29]Yes. Sorry about the quality of the paper. I only got this paper about an hour before I came live here. So I've not seen this paper anywhere. This is the first time I'm seeing this paper made 2025. Right? So stop complaining about the quality. It's what I have.

[00:43:44]Right? So a gas occupies 2 m cube. So volume let's call that V1 is 2 m cube.

[00:43:54]It's temperature. So your temperature T1 is 27°. So first of all when it comes to uh gas laws we have to convert to Kelvin. So that's 27 + 273.

[00:44:08]So that works out to 300 Kelvin. All right. So that's step one. Um we also know the pressure. The pressure is 1 atmosphere. So P1 is one atmosphere.

[00:44:21]Uh they also told us that the pressure changes to two. So P2 is two atmospheres.

[00:44:31]Um T2, we don't know what this is, right? Um but what else we know, right? The volume is so V2 is 1 m cube.

[00:44:44]Okay, so what we using here? We're using the fact that we using the combined gas laws. P1 V1 over T1 is equal to P2 V2 all over T2. So we just need to substitute here. So the initial pressure is 1 * V1 which is 2 all over T1 which is 300 K is equal to P2 which is 2 multiplied by T sorry by V2 which is 1 all over T2. If I rearrange this formula here, I'll get T2 is 300 * 2 * 1 all over 1 by 2. So this will cancel here. So you'll end up with 300 K. Okay? So 300K is exactly what the original temperature was. So that means you're going back to 27°, right? This here is actually 27° C. So the answer is going to be B, right? The answer is B.

[00:46:00]right? Um let's see.

[00:46:09]Right. So this is 20 22 right? This is the third one you know 23rd one.

[00:46:32]This one could potentially be a new question. this one right I don't remember seeing a question um asking us about Charles law which graph here represents Charles law question 23 right uh some of you all asking about the gas law question we have to use the combined gas law here right that's what you're using in there And normally when you're using the gas laws, you have to write down your initial conditions and your final conditions. Once we do that, you need to make sure that temperature has to be converted to Kelvin. If the temperature is not in Kelvin, then your calculation is going to be incorrect.

[00:47:20]Right?

[00:47:25]All right. So for this one here, we're talking about Charles law. So first of all, Charles law says this uh volume is proportional to the absolute temperature. Okay, so therefore V is equal to K by T. So therefore that's going to be a straight line that passes through the region. So the answer is going to be D. Now first of all this this Cxc question here is lacking something because they need to tell us what T is. This T here is actually in Kelvin. Has to be in Kelvin for this to make sense. Okay? because if it was not in Kelvin then the graph would have looked like this.

[00:48:02]We plotted uh volume against temperature in degrees Celsius the graph would have looked like this.

[00:48:08]Okay. So Cxc should really tell us that T is in Kelvin. They've told us nothing.

[00:48:12]Right.

[00:48:14]So that's 20 23.

[00:48:22]Question 24. Which of the following right is most suitable for a clinical to thermometer?

[00:48:31]Right. So we got thermometers in the paper too. So somebody's asking what if that's a radioactivity question. Nope.

[00:48:51]All right, let's see what people saying.

[00:48:56]People saying B.

[00:48:58]Okay, so clinical thermometer clinical thermometer goes from around 35° C to about 43°C, right? Because normal body temperature is around 37.5.

[00:49:14]Okay, so the only answer that makes sense here will be B, right? You don't need the thermometer to go zero cuz if it reaches zero then the person is already frozen to death. It can't go up to 100 because by the time you reach 100 the person already boiling, right? So the only correct answer would be 35 to 44 in this case here. Okay? So that's 24.

[00:49:37]Uh question 25 is some of you all would have done this as an SBA lab at the beginning or sometime in form form. So you all should know this one here we have molten napalene.

[00:49:51]So some of you all would have used either napalene or steeric acid to draw a cooling curve.

[00:49:59]So we have four graphs here and they said the molten napalene is at 100° C.

[00:50:07]It's allowed to cool to room temperature. If the napalene has a melting point of 80° which graph best represents this? So, we're talking about a cooling curve here, right? We're saying see. So, first of all, let's draw what this is supposed to look like. So, to begin with, you want to draw a cooling curve here for napalene. We start off at 100°C. So, this will be temperature in degrees Celsius. This is time in seconds. So what really supposed to happen is this.

[00:50:48]It's going to cool down. Then when it starts to solidify, you're going to have this flat region here and then it's going to continue cooling. So that's what the cooling curve is supposed to look like. When you look at the answers here, the only one that kind of resembles it is C, right? C is the only one that kind of looks like it.

[00:51:07]So that's 25.

[00:51:16]Right. Question 26.

[00:51:20]Which of the following reasons are reasons why a hot liquid placed in a doublewalled vacuum flask retains heat for a long time? So, we're talking about um the thermos flask here or the vacuum flask. What's the answer for this one?

[00:51:36]26.

[00:51:58]Right.

[00:52:05]So people saying beef. So first of all um silvered inner walls reduces the the loss of heat by radiation.

[00:52:16]Okay that's true. The silvered outer wall helps to absorb heat from the surroundings. That is not true. Black surfaces absorb heat. The evacuated space between the double walls reduces the loss of heat by conduction. Yeah, that makes sense. So, one and one and three, which is B, right? What do you all say? B. Yeah, right. So, that's 26.

[00:52:49]Question 27. They bring a next gas laws inside.

[00:52:54]All right.

[00:52:57]So a light bulb is filled with a gas at a temperature of 293 Kelvin. If the initial pressure is P, so P1, initial pressure is given by P, your initial temperature is given by 293 Kelvin.

[00:53:18]All right. Um what would be the pressure when the temperature increases to 360? So your new temperature is 360K.

[00:53:30]Your new pressure, we don't know, right? We don't know the new pressure. So first of all, when you look at the information given to you here, all right, you will notice that there's no volume given. So you're going to assume it's the pressure law and we're going to say P1 over T1 is equal to P2 over T2. Now they already gave us the temperature in Kelvin already here.

[00:53:54]So we can say P1 which is P divided by P1 which is 293K is equal to P2 which I don't know and that is over 360. So you want to work out P2. If you want to work out P2 we're going to cross multiply. We're going to say this by this is equal to this by this. So when you work this out here, we're going to say 293 P2 is equal to 360 * P. So therefore, P2 is equal to 360 over 293 * P. So which answer is that? 360 over 293 by P. Answer is A, right?

[00:54:45]So that is 27.

[00:54:56]This is 28 here. All of these are repeat questions. I've seen most of these already.

[00:55:04]Which diagram best illustrates convection current in a liquid? Right.

[00:55:11]Which one best Illustrates convection current in a liquid.

[00:55:39]Right. I seen D. Which one makes the most sense? Um yeah, D makes the most sense. When you have convection currents, this is what happens. We get this type of behavior, right? So D is the only one that makes sense, right? Question 29.

[00:56:04]We have two types of radiation falling on your left hand, right hand. Um her left hand feels hot but does not become tanned and her right hand does not feel hot but eventually becomes tan. Which radiation is which?

[00:56:34]Right.

[00:56:42]I see the majority of you all saying C.

[00:56:45]All right. So, first of all, they said um her left hand feels hot, right? So, if it feels hot, that's infrared radiation.

[00:56:56]So, the left hand has to be infrared.

[00:56:59]Now, based on the answers here, the only one will be C. And on the right hand it doesn't feel hot but it becomes tan. So ultraviolet is what causes it to become tan. So the answer is C in this case here. Okay. So that's 29.

[00:57:14]Uh question 13.

[00:57:25]Using electrical method, a student carries out an experiment to determine the specific heat capacity of a solid.

[00:57:31]Which of the following equations should be used?

[00:57:36]Well, I have a problem with this question because CXA has not told us what any of these letters mean.

[00:57:42]They haven't told us what F is, what D is. I have no idea. So, how students supposed to answer this?

[00:57:59]Right. Okay, let's see what's happening here. So, first of all, the heat supplied by your heating element will be I by V by T, right? So, that's current, voltage and time and that is equal to M C delta theta, right? That's essentially what we have to use. So, I can write this as MC delta theta is equal to I VT.

[00:58:26]So therefore C is equal to I V T all over M by delta theta. So the only one that makes sense here is A. Right? A is the correct answer.

[00:58:42]Right? So that's number 13.

[00:58:58]We have an instantaneous profile of a wave traveling across a water surface.

[00:59:03]From the information, the frequency is what?

[00:59:51]Right. So, what do you all think is the answer for this one here? Okay. So, we have a wave and then based on the wave, we try to figure out what is your um period of this wave here.

[01:00:18]So you want to work out your frequency.

[01:00:20]Now frequency is given by one over your period. But if you notice something here, we have a waveform, but we have position on the horizontal axis. There's no time involved here. So there's no way, literally no way for me to calculate this. The answer is going to be D, right? Right, the answer is going to be D. Right? If I want to calculate my frequency, your wave, you must have t here, right? And you'll have displacement here, right? So make sure you can't calculate your frequency from this particular diagram.

[01:01:02]Right? So that's 31.

[01:01:04]What about question 32?

[01:01:50]Right? So we want to get the wavelength of this wave here. So if you want to calculate wavelength, if I have a wave that looks like this. So wavelength is actually wait hold on.

[01:02:07]Right? Right. So let's say there's a wave here from here to here that's two consecutive uh crest that's a wavelength from here to here that's also a wavelength. We also can look at one crest one trough. So from here to here right this is also a wavelength here. So based on the diagram here um let's see PS looks like A is the answer here right?

[01:02:33]If we look at A here A will be the answer. So from P to S, that's two consecutive crests. So that's your wavelength here.

[01:02:54]Right. So that's um 32.

[01:02:58]What about 33 here? We want to know which um which one of these here, right?

[01:03:03]Which one of these? Um, right. Basically, which one of those are the um the wave equation? Which one is actually the wave equation? Right.

[01:03:37]Right. Which of the following equation expresses the correct relationship between uh wavelength, speed and frequency, right? People saying a so the wave equation is given by V is equal to F lambda. So um we're looking to see if I want to rearrange this frequency will be V on lambda that's one equation um or we can say that lambda is V on F right so these are the equations we're looking for so A has to be the correct answer so that's 33 question 34 is based on these two waves here.

[01:04:30]We're talking about pitch and we're talking about loudness, right?

[01:04:48]White can't be D. Uh, which D you talking about? This one.

[01:04:56]Because this is the formula for for wavelength, right? This formula is wrong.

[01:05:32]right? So for this one here, let's see what's happening. So first of all, which one is louder? So loudness depends on amplitude. So if we compare the two amplitudes here, we can say that Q has to be louder, right? So Q is louder.

[01:05:46]That has to be true. Q is louder. Now we need to talk about the higher uh pitch.

[01:05:52]So first of all, pitch depends on frequency.

[01:05:58]Right? Pitch depends on frequency. Now if we compare the two waveforms, you will realize that the higher frequency has to be this wave here as compared to Q. So P has to be the higher pitch. So the answer is going to be D in this case here. Right? D is going to be the answer in this case here.

[01:06:18]Yeah. P has a higher pitch. Yeah. Right.

[01:06:30]Right. So that's 34.

[01:06:32]Uh question 35.

[01:06:40]All right. So we have a a waveform here and we want to know the amplitude of waveform here. But there's a easy question again. What's the answer for this one?

[01:07:05]Right? We're saying a so the amplitude is actually here. Right? But if from here to here is 8 cm, we just need to divide 8 by two. So we get four. So the answer is eight. Okay.

[01:07:22]Uh question 36 is based on a converging lens.

[01:07:30]Which line lies along the principal axis of the converging lens?

[01:07:42]Which line lies along the principal axis?

[01:07:57]Right? I've seen D people saying GK.

[01:08:00]Yeah. This line here is your principal axis. It's the horizontal line that passes through the optical center of the lens. So the answer is D. Right? The answer is D.

[01:08:34]All right. So, we have a diagram here.

[01:08:35]It shows two coherent light sources producing an interference pattern on a screen of bright and dark fringes. Um, the reason for the formation of the bright fringes, what you're going to say there for the bright fringes, why do we get bright fringes here?

[01:09:02]Right.

[01:09:09]I've seen people saying C.

[01:09:13]All right. Um, so if you get we're speaking about a bright fringe. So if you have bright fringe, you have constructive interference. So what that means is that two waves right are going to reach at the same point at the same time. Or we can say that two waves are actually in phase with each other. Right? So what's happening here is this. This is what needs to happen in order for constructive interference to take place.

[01:09:40]The two waves have to be exactly in phase. Okay. So um all the crest phase along the point. Yeah, that makes sense.

[01:09:50]Cress a larger. Yeah. Answer is BC, right? Constructive interference.

[01:10:03]Right. That's 37. Question 38.

[01:10:09]The refractive index of a transparent medium with critical angle C for light traveling from the medium to air is what? So they want to know what is the critical angle here?

[01:10:28]Sorry refractive index as right I've seen people saying so first of all when it comes to critical angle you need to have a ray traveling from right so I'm just going to use they call it a transparent medium right I'm just going to call it glass let's call this air right so when we speak about critical angle this your normal here what's going to happen is that this ray is going to travel along the boundary so that's going to be 90° and this here is going to be your critical angle now if I were to write out the refractive index for this glass here that refractive index would be sin I over sin r which is s of 90° this is 90° here divided by s of C, right? That's the formula we're going to use to calculate our refractive index. So, the answer is D.

[01:11:40]Question 39. Which of the following statements about waves is true?

[01:11:46]What's the answer for 39?

[01:12:14]chocolate ice cream for sure.

[01:12:28]All right, let's see in B. So first of all, uh true for all waves. Um all waves undergo reflection, refraction, and defraction has to be B. All right, so that's 39.

[01:12:50]What about this one here? Question 40.

[01:12:53]Which of the following objects can detect X-rays? How do we detect X-rays here?

[01:13:20]Right. I seen a Yeah. photographic film.

[01:13:22]That's how we detect X-rays.

[01:13:25]Um, question 41.

[01:13:35]Which of the following laws are laws of refraction?

[01:13:42]The answer for 41.

[01:14:12]All right. So for this one here, we're talking about the laws of refraction. So don't don't get confused with this one.

[01:14:17]Right? So sin I over sin R is a constant. That's true. Angle of incidence equal to the angle of refraction. That's not true. The incident ray, the refracted ray and the normal at the point of incidence all line the same plane. That's true. So it's one and three which is B.

[01:14:47]Right. Question 42.

[01:14:50]Which of the following equations cannot be used to determine power dissipated?

[01:14:55]So there are several formulas to calculate power when it comes to electricity. Which one right which one cannot be used?

[01:15:22]Right. I as um say in C.

[01:15:30]All right. So first of all uh we have P is equal to IV. Right? We have P is equal to I^2 R. We also have P is equal to V ^ square and R. These are all formulas to calculate power. So the only one that doesn't belong here is C.

[01:15:48]Right? This this is not how we calculate power. So that's wrong. Uh that's 42.

[01:16:00]Uh question 43. What is rectification?

[01:16:02]Or rectification can be best be done using what?

[01:16:39]Right. So, but this one what people saying D. Yeah, we're using a semiconductor diode. So, rectification is if we have an alternating current, right? And you want to convert that into a DC current. If we use a diode, this is what we're going to get, right? The waveform is going to look something like this. So that's rectification in a nutshell.

[01:17:01]So that's uh 43.

[01:17:05]Question 44.

[01:17:12]An ideal transformer has a primary secondary turns ratio of 1:3. So they're telling us that the turns ratio number of turns in the primary to number of turns in the secondary the ratio is 1:3.

[01:17:27]Now an alternating potential difference of 200 volts is applied to the primary.

[01:17:32]So this is 200 volts being applied here.

[01:17:34]Now since the ratio is 1:3 we expect on the secondary it'll be three times. So that's going to be 3x 200. That's going to give us 600 volts. So this is the voltage on the secondary here. Now that voltage here right an alternating current potential difference a 200 is applied to the primary and a resistance of 200 is attached to the secondary. What's the current in the secondary? So first of all on the secondary coil basically we have this resistor here right uh this here is 200 ohms right but the voltage that we have across this here is 600 volts okay so the current that is going to flow here I so I is V on R so the voltage here is 600 over 200 so that's going to be 3 amps So the answer is going to be D. Right.

[01:18:40]Right. Question 45.

[01:18:53]Right. So we have um have a circuit here. The ammeter reads 04 amps and the voltmeter reads 6.

[01:19:03]What's the resistance? So this circuit is what we actually use to measure um yeah this circuit is what we use to actually measure resistance. So what's the resistance in this case here?

[01:19:20]All right. I've seen people saying B. So all we're going to do, we're going to say R is equal to V / I. So the voltage reading was 6 volts over the current which is 04. So that's 6 over 4 or 3 over 2 which is 1.5. Right? So this is 1.5 ohms. So the answer is going to be B.

[01:19:45]Right? So that's 45.

[01:19:56]All right. Question 46. Which device allows one circuit to be switched on or switch another circuit on and off without direct contact? What are we talking about here? Can I see it?

[01:20:25]Right. I seen a Yeah, it's a magnetic relay, right? We use a magnetic relay to switch a secondary circuit on. There's no physical contact between two circuits, right?

[01:20:38]Question 47.

[01:20:49]So you have a diagram here. It shows a straight wire carrying a current into the plane of paper. So the current is flowing into the paper and you want to represent or which represents the magnetic field around the wire, right?

[01:21:14]Right, everybody saying B. Uh, yeah, B makes sense, right? Basically, you have to use your your right hand in order to do this, right? Your right hand grip rule. So, the current is going into the paper. So, your thumb goes into the paper and these fingers pointing the direction of the magnetic field. So, it's going to be B.

[01:21:38]So that's 47.

[01:21:48]What about 48? Here we have two light aluminum spheres A and B suspended by insulating threads. If they come to rest as shown, what force is keeping them apart?

[01:22:22]All right, people saying C. Yeah, it's electrostatic. I agree with that. Right.

[01:22:27]Um, what else we have here? That's 48.

[01:22:42]What about 49? We have a diagram here.

[01:22:45]We have two resistors, R1 and R2. One is 6 ohm, one is 4 ohm. And they gave us a current flowing through R2. They want us to work out the current through R1.

[01:23:00]I know for this one some students you just learn up the answers but you don't have to, right? You need to know how to work it up, right? I feel some of you learn the answers, right? So, first of all, we could you know the current flowing here.

[01:23:23]So what I could do I can work out the voltage across this parallel combination here. So that voltage here is equal to I * R. So this current here is 1.8 amps * 4.

[01:23:38]So that's going to be 1.8 by 4. That's 7.2 volts.

[01:23:43]Now that same 7.2 volts is actually across this resistor as well cuz they are par in parallel. So if you want to get uh the current in R1, you want to get this current here. Let's call that I can use I is equal to V on R. So the voltage across R1 is the same 7.2 volts divided by R which is 6 ohms. Right? So that is 7.2 / 6 and we're going to get 1.2.

[01:24:11]Right? So yeah, you are correct. The answer is eight.

[01:24:16]Right.

[01:24:20]Question 50.

[01:24:37]Right. Which of the following uh current time best describes a DC current?

[01:24:43]Question 50.

[01:24:56]no that's fine you know you can memorize certain things you know just when you get questions make sure and read them over cuz I remember a lot of students in one particular year they learned of the answer I think the answer was voltmeter or something so and then CXE changed the question slightly and then some students came and they told me say the answer is voltmeter, right? And then when we check the question, we realize no, they change the question. So just be careful. That's all I'm saying. Nothing wrong with learning up the answers, right? So for this one here, you want a DC current. People saying the answer is D. Yeah, it's going to be D, right?

[01:25:41]Oh, this this was the same question I was talking about here. This particular question here, they change the question one in one year and people got it wrong.

[01:25:49]An amter has a very low resistance so that it can be placed in what?

[01:26:07]Right. What's the answer for this one?

[01:26:20]Right? As in being so first of all we talking about an amter. When it comes to an ammeter an amter is connected in series with a component if you want to measure the current. So it has to be in series and you don't want to affect the circuit in this case here. Right? So it's series and the answer is going to be B. Yeah.

[01:26:42]So that's 51.

[01:26:45]Uh question 52.

[01:26:58]So we have a a combination of logic gates here and they said um what is the output R and S when the input of zero and zero is made at P and Q. So, we put in a zero here and a zero here. We want to know what's coming out at R and what's coming out at S.

[01:27:22]Yeah. Vote meter would be in parallel.

[01:27:24]Yep.

[01:27:32]So, I seen you all talking about releasing papers. CXE never releases any multiple choice papers, right?

[01:27:39]All of these multiple choice papers that you'll see are stolen papers.

[01:27:44]Not by me, right? But TX never releases multiple choice. You are not supposed to have any multiple choice paper.

[01:28:07]All right. So first of all this gate is an AND gate. So for an AND gate the only time you get a one is if you have a one and a one. So this has to be a zero. Um in the case of this is an orate the only time you get a a one for an orate is if you have a one and a one. So this is also going to be zero. So the answer is going to be a. All right. The answer is going to be a here. Okay. Be careful with this one here. This looks like something they could easily change with respect to the um question.

[01:28:42]So that is 52.

[01:28:50]This one here is 53.

[01:28:57]So they want us using the information in the circuit which pair of values of I1 I2.

[01:29:14]So if I had to do a question like this here what I'll do I'll take these two resistors here. I'll try to work out the total resistance. So 1 / RT will be 1 / 2 + 1 / 4. So therefore 1 / RT is equal to that's a half plus a quarter. So that's 3/4. So therefore RT the total resistance in the circuit is 43 ohms.

[01:29:40]Right? So what I can do I can work out the actual voltage across this parallel combination here. I can work out that voltage by using V is equal to IR. So our voltage is I by R. So the current in this case here we have 6 amps multiplied by the resistance which is 43. So that's going to be 42 8 vol. So we have a 8 vol actually across um the 2 ohm and the 4 ohm. So I1 is equal to V / R which is going to be 8 / 2 which is going to be 4 um amps.

[01:30:19]I2 is same V on R. So this is going to be 8 over 4. So we get 2 amps. So the current will be 4 and 2. So the answer is going to be D. Right? So there's a way to calculate it. Right? There's a way to calculate it.

[01:30:48]Right. Question 54.

[01:30:57]Right. Which of the following properties describe an alpha particle? Right. What is 54?

[01:31:15]All right. Uh people saying so it's an alpha particle, right? Positively charged, very penetrate. No, sorry. Well, I say very penetrative. It's positively charged, not very penetrating. The answer is B, right? Alpha particles have a positive charge, but they are not very penetrating. Right? The answer is B.

[01:31:45]Okay.

[01:31:46]So, that's 54.

[01:31:50]What else we have here?

[01:32:06]When a conductor rotating on a uniform magnetic field induces maximum instantaneous current when the conductor cuts the magnetic field lines at what?

[01:32:23]What's the answer for this one here?

[01:32:47]Right. People saying C. Yeah, the answer is going to be C. For this one here, if you want maximum instantaneous current, right, you need to cut at 90°. Okay, there's one that you probably just learn off, right?

[01:33:05]Uh what about 56 here?

[01:33:10]Which of the following statements about a proton is not true?

[01:33:16]Which are the following statements about a proton? Right? We talk about a proton here.

[01:33:37]Right. As seen A is coming through.

[01:33:39]Yeah, it is E. They said which is not true. Right. Has the same mass as an electron. Remember an electron has a relative mass of 81 over 1840. Okay. So the proton and electron they don't have the same mass.

[01:33:54]Uh question 57.

[01:34:04]Okay. So, the activity of a radioactive substance was measured at specific intervals over a period of days. And the halflife is what? What's the halflife?

[01:34:19]Right. People kind of blurry here. So, this might be a guess one.

[01:34:56]right? So you guys are telling me the answer is B. So first of all, we can start at let's say 400 and let's see how long we take to reach 200. So you'll draw a line going across here, right?

[01:35:08]And then we're going to come down, right? So if we come down here, you're going to get a value of two two dates.

[01:35:15]So it's going to be right. Question 58.

[01:35:29]Which of the following statements about radioactive decay are correct?

[01:35:57]Right. So I see C is coming through. So first of all they said which is true about radioactive decay are correct. It is dependent on conditions external to the nucleus. Nope. It is independent.

[01:36:09]It's a random process. Yep. It's due to changes in the nuclei of atoms. That's also true. So it's two and three. So the answer is C, right? That's 58.

[01:36:24]Uh question 59.

[01:36:33]We have an isotope here. So you're probably not seeing this properly here, but we have uranium 2 3492, right? and you're changing to toum 230, right? Um 90. So they said an isotope of uranium changes to to thorium. This is an example of what what kind of decay is this?

[01:37:21]Right. So we have an isotope of uranium 234.

[01:37:26]Right. Uranium which is 234. It's changing to toum. And they want to know what is this an example of.

[01:37:38]All right. People saying D. So first of all, this is decaying here. We need to balance our mass numbers. So you're missing a four here and you're missing a two here. So the only particle we know that'll do that is an alpha particle. So it's an alpha decay taking place here.

[01:37:54]And for the last one, question 16.

[01:38:02]Right? Again, sorry about the quality of the paper.

[01:38:06]Right? So which equation is correct? So the first one we have radium 226.

[01:38:12]Um this looks like 88 I think. Uh that gives us radon 222 and this is 86 and we get beta.

[01:38:26]The second one we have carbon 14 6 changes to nitrogen 15 7 plus a beta particle. The next one here is radium 226.

[01:38:41]We have 88 and that changes to radon 222.

[01:38:47]Um, it looks like 86 I guess, right? Plus alpha and then we have carbon 146 changes to nitrogen 147 plus alpha.

[01:39:03]Right? So they said which one is correct, right? Which one is correct here?

[01:39:18]Right? I've seen people saying C, which is this one. So let's see. Um, we have 226 here and 222. So you're missing four. We have 88 here. We have 86.

[01:39:28]You're missing two. Yeah, this one is correct. Right. The answer is C. Right.

[01:39:32]The answer is C.

[01:39:36]Right.

[01:39:38]All right, guys. So again, right, this is May 2025. Right.

[01:39:44]Some of these questions, chances are they're going to repeat tomorrow. So this is all the time I have guys. So I hope that the session was beneficial.

[01:39:52]Please remember to hit like and subscribe. Right? You all can let me know how the exam was tomorrow. I know it's going to be a good exam, right? So guys, enjoy the rest of your night.

[01:40:02]Right? Go get some rest, right? Don't spend whole night just studying paper ones, right? I'm sure you've done sufficient paper ones. Once you've done about eight exam sittings, you should be all right. Okay? All right, guys. So, that's it for me for tonight. Enjoy. All right. Take care, people. Later.