00:00 Hello everyone, my name is Tijani Muftau Oladipupo I'm your Physics teacher, the topic before

00:20 me is position, distance and displacement.

00:24 At the end of the lesson, students should be able to distinguish between displacement,

00:33 distance in a translational motion, the instruments used for measuring the length of an object.

00:41 What is position?

00:43 Position is distance and direction of an object from particular point of reference.

00:49 So this point of reference could be the starting point when we consider a 4-cardinar point.

00:56 And for a 4-cardinar point from elementary or elementary mathematics, we have 4-cardinar

01:02 points which include the knots, the west, the east and the south.

01:09 So an object could start from a reference point which is this starting point and move towards

01:16 this direction.

01:17 So any object starting from this is in between two directions, which is between the knots

01:23 and the east.

01:25 So another object could move in another in this particular direction, which is the south

01:29 and the east direction.

01:32 So this position we are talking about, it could be negative sometimes, depending on where

01:37 the body is moving from on the 4-cardinar point.

01:40 I'm still going to make reference to this.

01:42 On the 4-cardinar point, we have 4 different axes, which include, this is always the positive

01:49 for those that are mathematically inclined.

01:53 This is the negative, this is positive, this is negative and this is negative.

01:59 So it could be zero if the object is starting from the origin and it could be negative if

02:06 it's actually moving towards the west direction.

02:11 And lastly, it can be positive as well if it is moving towards the east direction.

02:21 So what is distance?

02:22 Distance is the total movement of an object without any regard to the direction.

02:29 Yeah, it's possible for me as a teacher to move in the line of direction of the class without

02:36 considering the direction.

02:38 So if you are moving without considering any form of direction, what is actually happening,

02:43 the kind of motion in that regard is referred to as the distance.

02:48 That is the distance of an object.

02:50 But when we are pushing into consideration, the direction as well as the distance, that

02:56 is when displacement comes in.

02:59 But sometimes, we might be interested in calculating the total distance of an object.

03:05 For an object A, let's assume we have an object A moving from point A. An object A moving

03:12 from point P to point Q. This is the object, it's moving from point P to point Q. If we want

03:21 to calculate, if we take the distance of this one to be 3 km and we have another object

03:26 B moving on the same point of reference, which is P to Q on a distance of let's say 10 km.

03:36 If you actually want to calculate the distance, we are not considering the direction.

03:41 We will sum up the two distances.

03:45 So the summation of these two distances, the distance is actually going to be 8 plus 10,

03:53 which is what's in total, we give us 18 km, and that is how the distance of an object can

04:00 be measured and calculated.

04:04 However, on the other hand, when we consider the distance and the direction of an object,

04:12 then we make reference to displacements and is a major difference, a major distinction

04:18 between distance and displacements.

04:25 Displacements is divine as a change in the position of an object which respects to direction.

04:34 So we also need to know that I said it at the beginning that distance is just a scalar

04:40 quantity.

04:41 And when we say something is a scalar quantity in physics, it simply means it's only

04:45 a magnitude, and the magnitude here we are talking about the size.

04:50 But when we consider the direction, it means there is possibility for an object to move

04:55 in the north direction or the south or the east.

04:58 In fact, sometimes you can move in the left or the right direction of a particular object.

05:05 So when those directions are taken into consideration, we have what is called displacement.

05:13 But the displacement of an object is always the word scalar quantity.

05:19 Having known the definition of displacements, displacements, the formula for displacement

05:25 of an object can be mathematically given as data H. The symbol there means data H, data

05:35 X, which is mathematically equals to X of F minus X of I.

05:42 The X of F means the final position where the object gets to.

05:47 And the X of I means the initial position, that is like the starting point where the object

05:53 is moving.

05:54 So let's take a question, a beautiful question, example of displacements.

05:58 John travel 250 miles to north, but then about to south for 105 miles to pick up a friend.

06:08 What is John Trotard's displacements? As said earlier, we all know that displacements

06:13 is changing the position of an object.

06:16 And as a result, we are so much in consideration of the direction.

06:24 Looking at, let's put this in the perspective of four cardinal points.

06:28 We have John traveling for this, that is 250 miles.

06:36 And it's going back south, which is 105 miles.

06:41 That is in the south direction.

06:42 This is going in the north direction.

06:44 If you actually want to find the displacements going by the formula that we have, data X is

06:51 equals to X of final minus the X of initial.

06:57 So since it's going in opposite direction, it's one of the rule of vector, it's one of

07:02 the cases of vector that must be put into consideration.

07:06 If you have to vector going in the same direction, you add it up.

07:10 If you have vectors going in opposite direction, you subtract.

07:13 If you have to vectors that inclined at 90 degree, that will be resolved by Pythagoras theorem.

07:20 But since these two vectors are in opposite direction, it is very easy to subtract and get

07:28 the resultant displacement.

07:30 So this is going to be 250 minus 105.

07:36 And after subtracting, we have our results to be 145 miles.

07:43 And this is the simplest way of calculating anything on that displacement.

07:51 There are some differences between displacements and distance of an object.

07:58 But before that, we need to know that there exists a similarity between displacements and

08:06 the distance.

08:07 If we look at the two of them, they are one of the major key measuring fundamental quantity.

08:16 And that is the displacement is actually measured in meter written as this.

08:24 And the distance as well, the unit, the standard unit, that's how unit is also meter.

08:31 So it should be noted that both displacements and the distance have this in common.

08:38 They have in common the units, which is what's meter.

08:42 But the major difference between them is what we're going to look at now.

08:46 The first one is the complete length of the path between any two points is called distance

08:51 that has been well established.

08:54 This means it's the direct length between any two points when measured along the minimum

09:00 path of minimum path between them.

09:03 The other difference we have mentioned at the beginning is that distance is scalar quantity

09:10 as it only depends upon the magnitude and not the direction.

09:14 Anything distance, we are only moving on this straight line.

09:17 So we are not considering the not direction or the east or the south.

09:22 But as for displacements is a vector quantity as it depends upon both magnitude and direction.

09:29 So distance can only have positive value.

09:33 It has never happened in the world of science for distance of an object to be negative.

09:39 So distance will always be positive.

09:41 However, displacements, considering the four cardinal points that I explained with initially,

09:48 the displacement can be negative, if it's coming from this side, it can be positive, if

09:54 it's on the right direction, on the left direction, it can be negative, if it's on the

10:00 up direction, that is going towards the north direction, it will surely be positive.

10:06 And coming down from the point of origin, it can be what?

10:11 It can be negative.

10:16 So measurement of length, how do we measure length?

10:21 We know that length is just like distance covered by an object.

10:27 And as such, there are so many things that can be measured about the length of an object.

10:35 We might be interested in the thickness, we might be interested in the depth sometimes

10:39 or the height.

10:40 So measuring the distance of an object is very, very much important in physics.

10:47 And there are about four or five important things that we use to measure them.

10:53 The number one is Rula.

10:55 We use a Rula to measure the distance of an object.

10:59 We can use the meter scale.

11:03 We can use a measuring tape, the veneer caliper, and the last one, which is the most important

11:09 one is the micrometer screw gauge.

11:12 However, before most of these, the modern equipments are discovered, our forefathers, they

11:23 use the asian instruments to do measuring.

11:26 Like in a farmland, in order to position, to give a position that this is the region of

11:34 my land, they use a particular object to measure, which we are going to consider now.

11:39 So the asian instruments can be the, we can have the footstep, which is one of the asian instruments

11:46 that they use to measure.

11:48 We have the rope, we have the antspan, and we have the ants length.

11:53 You look at, in the case of the ants length, for those of us that do go to the electronic

11:58 workshop or to get something like a wire from most of these people that sell it, they use

12:07 the ant, the ant ants to measure.

12:10 Although sometimes it is not always accurate, but they already give it a value to it.

12:16 But in the modern time, these are the instruments that we use to measure.

12:21 They include the ruler, the metal rule, or they put some times, we have the veneer caliper

12:29 and the micrometer school gauge.

12:32 So we look at, we examine them one after the other.

12:39 So the first one is the ruler.

12:41 We all know that a ruler is a common measuring device that is ubiquitous, can be found everywhere

12:50 in our lab at home, and we use it almost every day.

12:54 So the ruler, most times, can be used, there is limitation to the use of ruler.

13:01 Most of the time we use ruler to measure a distance that is not above 100 cm, and because

13:10 I'm saying this, I need to let all know the relationship between centimeter and meter.

13:17 You need to know that one meter is equivalent, is equal to 100 cm.

13:24 So ruler can be used to measure a very short distance, that is not as long as the length

13:30 of this slide.

13:35 The other one is the tape rule.

13:37 For a distance that is more than 100 and above, that is more than 100 cm, we use more than

13:45 100 cm or up to a feet, we use the work, we use the tape rule.

13:50 So the tape rule can be found used by the tailor, can be used by engineers, sometimes depending

13:57 on the nature of the job.

14:01 So there are two types of tape that we really need to know.

14:05 The tape measure, the retractive tape measure and the surveying tape measure.

14:12 The tape measure should be your choice when working in the field of cap and tree, construction,

14:17 surveying, sewing, engineering, etc., etc.

14:22 So it has a good resolution, which you will find some of the gradated width, even one of

14:28 a 36 inch increments, but in most cases you will find it's care similar to a ruler.

14:37 So, but in the case of the surveying tape, that one can be used to measure a wide range

14:44 of distance.

14:45 Let's say we are considering, suppose you want to measure, suppose you are interested

14:53 in measuring the length of the plots of a particular land, we use the surveying metalwood,

15:02 it's surveying tape to do that, because it is beyond what the normal tape can do.

15:09 So the next one is caliper.

15:11 Caliper is another interesting and important measuring device and is having an accuracy of

15:20 about 0.001.

15:23 What this implies is that a caliper measure more accurate than the tape and the ruler.

15:32 For instance, we might be interested in measuring the diameter of a circular ball or the diameter

15:46 of a ball or a ball, anything.

15:48 We can be interested in measuring the diameter of a wire.

15:53 We use caliper to do that, although please note, I'm still going to say something about

15:59 this caliper, it's measured to this, which is some of those things that the metal rule,

16:06 the normal ruler cannot do.

16:07 So, it's measured to a degree of 0.001 meter, which is a very good measure in steel.

16:14 So, there are about three types of these caliper, but the most important of all is the digital

16:25 caliper.

16:26 Because, the digital caliper measures to the best of accuracy and is most time free from

16:34 error.

16:39 The last one is micrometer screw gauge.

16:42 So, I will explain based on the name.

16:45 Anytime, as a student, anytime you hear the word micrometer, micrometer means small, extremely

16:52 small, with high level of accuracy.

16:56 Although, I mentioned the fact that micrometer screw gauge can be used to measure the quantity

17:03 of their objects of a very small size, better than we use the metal rule and the ruler.

17:12 But, in the case of micrometer screw gauge, micrometer screw gauge measures much more accurate

17:20 than the veneer caliper.

17:22 Because the veneer caliper will measure, but is not as accurate as the micrometer screw

17:27 gauge.

17:28 And if you look at it, it's measuring to a measurement of 0.00 millilitre.

17:34 Telling us that, you know, it can be used to measure an infinitesimal object, a very small

17:42 object.

17:43 I've been interested in getting the thickness of a piece of book.

17:50 This micrometer screw gauge can do that.

17:52 So, in terms of accuracy, micrometer screw gauge measures much more better than the veneer

18:00 caliper.

18:01 So, if you are going to measure the thickness of paper, internal diameter of test to diameter

18:07 of a small ball with extreme accuracy, the micrometer screw gauge can be used to do that.

18:13 So, just like we have the digital caliper screw, advancement in technology has actually

18:21 helped the scientists to design and discover what we call digital micrometer screw.

18:27 So, it will reduce the stress and make work easier.

18:30 So, it is mostly used by engineers.

18:33 If they want to know the diameter, they want to know the diameter or the radius or the

18:39 radius of a ball or a beam that needs to be inserted to reinforce, to support the column

18:48 of the building.

18:49 So, they use this most times.

18:52 Evolution, differentiate between distance and displacement.

18:56 Number two, list any five instruments used for measuring the length of an object.

19:03 Thanks for watching, my name is Tijani Musaolado-Pupo, till next time.