now before your start okay can i get your to write the hypothesis first so the hypothesis in this case of course is a prediction all right what is what are you trying to find out can you guess this you're gonna test whatever you're trying to predict okay so you can you'll write this down first okay this is the hypothesis which is actually in pink okay so put a dash here as well so the what the parachute yes today we're gonna make a parachute okay the what the time thicken you're gonna also observe whether which one would fall to the ground faster which one will take a longer time to fall to the ground okay so you can you can say the is it the smaller the parachute or is it the larger the parachute will it take a shorter time to for it to fall to the ground or will it take a longer time for it to fall to the ground okay now do you all have your materials for today i think today's materials are much more on hand right which means you probably have all these at home so these are the materials that i have on hand as well okay i will do a little bit here and there to guide you okay so i have trash bags okay but for you just use a plastic bag why use trash bag because they are big so it's easier to cut okay so what you need right if you were to read this whole experiment have you read it or not step one to step 10 okay so let me just summarize this you you actually need two large squares i know y'all have not cut it yet okay so i'm gonna give you a time to cut it out you definitely need a long ruler okay if you use a short ruler it will be slightly more difficult so use a longer ruler is better but if you only have short ruler it's fine okay what you need to do you just have to cut out a 30 by 30 cm square let's try to measure this out and cut it out until you have two different parts for those of you who are done right you might want to cut out your strings okay so you got to cut two long pieces of string 45 cm each okay it needs to be long all right just in case all right because if it's two cannot be too short if it's too short you'll have your parachute will not be able to form so just take out about just measure about 45 cm and then you cut it now so let me tell you what is step you should be done okay are you done cutting all your trash bags ready or your plastic okay so here's the important thing you might be wondering how to tie a knot onto each corner of the square okay so of course you label your corners first a b c d in clockwise direction okay now what is step three now watch huh because in class a lot of my students asked me to help died a lot but in online class i cannot help y'all okay so you need to look at how i'm tying the knot now now please don't tie it to out okay the knot is just for you to secure the string later you're going to tie the string over the knot so the knot is just there to make sure the string has a better grip when you tie the string over it okay so tie a knot onto each corner so you have four corners right how you're gonna tie watch huh okay i think you all have to look here okay so this is the knot i'm gonna make sure my knot is only at this very end okay not so in please don't put it so in if it's still in your parachute will be very small then it there's no point cutting a 30 by 30 square okay so i take this what do i do to tie the knot easier i twist it okay twist it so it's much easier to tie the knot okay twist it accordingly this is only one corner later you all must do for four corners okay watch and then after that i just use my finger of course my finger is fatter yours your finger should be smaller than mine okay go around okay go around it go through the loop okay and just tighten it like that okay so you should just have four corners being tight now i have already four corners here then after that make sure your corners are right uh basically your other end of the string must be diagonal must go to mastai to here so once you're done with the four corners is the string part is very easy really okay so my model is this i did not tie the sweet around it but you're supposed to get something like that then write the string right i mean the sweet or eraser right it has to be tight here so this is your parachute it must be tight here secure the eraser or the sweet here in the middle [Music] tape it together like that with the string so let's talk about a precaution first okay while you are doing what did i say earlier look at number one i said that the sweets must have the same mess or whatever object that you all use to attach it to the x part to the string all right whatever your use please write down that that object must have the same mess correct or not i told you already you cannot have different objects on different parachute because that will be an unfair test the second precaution that i can write is the strings must the string should be tight a similar distance away from all four corners you cannot have strings that that is shorter in one end and longer at the other end then it will affect the parachute for sure okay the strings must all have the same distance the last one that i can think of is the parachute must obviously be dropped from the same height again you cannot have you cannot drop that one higher than the other because then it will be an unfair test already then you will have two change variables so all these are the precautions that you have to take note off okay can observation so like what i said earlier what do we observe so how observation you usually will answer the hypothesis okay so in this case we say that the larger the parachute you can also say the smaller the parachute but your time taken will be different so you can just say the larger the size of the parachute we know the longer the time taken for the parachute to fall to the ground come to your explanation okay you might say isn't this is similar to the exposed surface area what right but if you recall your p5 topic okay actually we did mention this term that is also tested in your forces topic okay so yes just now jaden already said the larger the parachute we know that there's gonna be more exposed surface area right in this case the parachute in contact with the air in contact with the surrounding air but here's the thing why do why do you then think right that the parachute will actually stay in the air for a longer time now let's say you are the one on the parachute okay and you and you jump off right the aeroplane or something all right you feel that there's this there's something pushing against you right you will say there's air there's air pushing against the parachute as well so if i were to draw out this particular parachute here for you to see so let's say this is a big parachute all right so this is a parachute so and then you have this person here okay now as his parachuting down there's actually this thing acting against the parachute is it air pressure no it's not air pressure like a good try we don't use air pressure there's this thing that is allowing this person to stay in the air for a longer time and that's why he would land safely he will land slowly okay this thing that is pushing is actually a type of force it's actually called air resistance okay that's why i bring up this experiment because this experiment talks about air resistance air resistance is also a form of friction and friction is a white friction it's a force so how do i explain this i say that the larger the size of the parachute the more the exposed surface area in contact with the surrounding air that's one hands right there's gonna be more air resistance so this is the important part here there's gonna be more air resistance acting on the parachute that's why it can stay in the air for a longer time now the next thing i added please you have to write this down all right i say that air resistance is a form of friction which is actually a force so friction is a force which also means you can say air resistance is a force as well okay and what is friction friction is the action when one surface or object rubs against another object or another surface and friction opposes motion but what is friction friction will always go the opposite direction so the meaning of opposes is goes the opposite direction of you