 Hello friends, welcome to this session on problem solving on physics. So what we are going to do here is We will take up a worksheet and then we will solve the worksheet Okay, so the idea is that you get a good comprehensive revision of all the questions in the topic, okay, so one by one will take up a worksheet and We will solve the worksheet now the best would be that before watching this video You take the worksheet yourself. It is available on the artist and then you solve the worksheet first Once you solve the worksheet in let's say half an hour time then you Check your solution with the given solution there itself and then probably you can come and see how we have attempted the same problems Now toward the end of the exam or towards the exam Sorry, what you can do is you can just have a run through with these questions once again and they will give you a good solid revision That graph, okay, so let's begin Here is the first question It says which of the following statements is correct So what is the statement? Which of the following statement is correct? So I went to the next just a minute. Let me switch on the Yeah, so which of the following statement is correct both speed and velocity are same Is it so no, how can velocity and speed are same? Then why do we have two different quantities? So both speed and velocity are not same speed being scalar velocity being vector So the very next, you know option if you see speed is a scalar and that velocity is a vector quantity, right? This is true. So the answer is B But it is always advisable to have a look on the other options as well is speed speed a vector No, this is a totally wrong statement and none of these now that we already have an option So this is also ruled out Okay, so the option answer is B, but let us also throw some light on what is speed and velocity So, let us say you start from your home and go to your school Okay, and here is you take a path like this and You reach your school, right now this path length if you drop measure Let's say you have a mechanism or you just check the speedometer of your Vehicle in which you are traveling. Okay, so if you just measure this using some mechanism, so don't go by my Drawing it may be not that accurate, but when you are measuring this distance, okay, or this path length So hence that is what is called as distance. So what is distance guys? path length Right, if you measure the path length in what units you'll measure in meters centimeters kilometers light years Is it a astronomical unit all are the all are all these are Units of distance. So if you measure this path length, you will find out your distance You'll get the distance and what is speed then so speed is nothing but distance traveled distance traveled Divided by time taken Okay Time taken time taken for what not for partying but time taken for traveling that distance, right? So let's say when you started from H your time is t1 Okay, and you finished time is t2. So let's say at 7 o'clock you started for the school 745 You are at school. So 45 minutes is what is time taken, right? So hence what is time taken we represent it as delta t delta t meaning change in the time change in the time meaning So, let's say you started at 7. So that is t1 745 is t2 So 745 minus 7 is 45 minutes. So we say t2 minus t1 is the change in time Okay, change in time of what start and end of the motion Okay, so hence what is speed given by we simply is nothing but Delta s is the let's say the path length this distance is Delta s. I'm saying Delta s Okay, so hence Delta s divided by Delta t, okay, or Right, you can write Delta s whatever is the path length divided by t2 minus t1 Why are we calling it a Delta s? So Delta s because you know, let's say if you're measuring something so um, you measure from let's say you have a This distance to measure so either you can start you can put a meter tape along it and measure from zero But let's say you do not measure from zero. So let's say this meter tape was zero and this was some X X meters are there, but let's say you are putting the meter tape like this Many times the meter tape is damaged or whatever So let's say this is the meter tape now Okay, just example i'm giving so hence at this point start and this point end Okay, so at start this point here measured s1 And end measured s2 along the scale. So hence how much is the distance guys The path length will be simply s2 minus s1 and this is what i'm calling as Delta s change in that Okay, so Delta s by t2 minus t1 is speed and what is the unit of speed? Unit is meter per second written as ms minus one Okay, other units are kilometers per hour Miles per hour light years per hour, whatever right like that. Okay, then what is velocity folks? Velocity, what is velocity? Velocity is displacement covered displacement covered By time taken again. So the what is the difference then? So clearly if now let me take another color to differentiate it So let's say in color is This one, okay So if you join h to s home to school like that This is displacement I'm writing as this right So displacement is the shortest distance between any two points in space, right? You know that so displacement time taken Okay, so hence let me now. Okay. Let me write with white only. So this is again here the shortest distance So displacement I'm writing and t2 minus t1 Change in time. Okay. Thankfully the units are same. So meter per second or kmph like that But this guy has a difference. This is a vector Right because s is in a particular direction to h. So you can have so many s's Possible with respect to h which are at the same displacement Okay, so hence if you draw or let's say you simply draw an arc with the radius hs So all these points if you check Or what they are at the same distance or same You know displacement from the point h all are same what I mean is if you measure this Or you measure this all are same. So how do I locate s? So hence a direction is very very important So and let's say you say that s is due east of h, right? So vector. So hence it is a vector quantity direction is important So vector quantity It's a vector quantity But for speed you never cared which direction you moved, right? So hence it is a scalar And that is what the question was about Scalar quantity. What are other vector quantities force acceleration? torque Yeah, electric field gravitational field all these are vector quantity. What does scalar quantity speed volume area time Temperature pressure density all these are scalar quantities. Okay, so I hope you understood this question So let's go to the next question now