P.7 SCIENCE TERM 2 SIMPLE MACHINES AND FRICTION

追加: 2026-05-12

[00:00:00]hello and welcome to the science class my name is teacher john i'm going to teach you science program seven term two premise seven term two and begin by looking at a topic a new topic the first topic in term two called friction and simple machines all simple machines and friction simple machines and friction and we shall begin by looking at friction what is friction friction is a force that proposes movement between objects in contact friction is a force that opposes movement between objects in contact friction is a force that opposes movement between objects in contact for example if i try to move this eraser on this board when i try to move there's a force that is opposing a force that is stopping me from moving this eraser on the board that force is called friction even when you are walking there is a force between your feet and the ground that wants to stop you from moving that force is what you call friction so friction is a force that opposes movement between objects in contact types of friction we have what we call static friction static friction then we have sliding friction or rolling friction then lastly we have what you call viscosity friction now what is static friction static friction is the type of friction found in objects which are fixed in one position static friction is the type of picture found in objects fixed in one position objects which are not moving objects which are static objects which are in one place they have what you call static friction they're number two we have what's called rolling friction also known as sliding friction this is a type of friction found in moving objects objects which are moving they possess what we call sliding friction or what you call rolling friction then we have to call this constant friction viscosity friction is the type of friction that is found in liquids and gases this is the type of friction found in liquids and gases so next we look at what we call function properties of friction properties of friction we have [Music] three or four properties of friction one friction is greater on rough surfaces friction is greater on rough surfaces surfaces which are rough they have more friction surfaces which are smooth they have less friction that's why number two we are saying friction is less on smooth surfaces friction is less on small surfaces surfaces that are smooth have less friction surfaces that are rough have a lot of friction number three weight increases friction the more the weight the more the friction that's why if you look at the shoes worn by somebody who is heavy they wear out quickly compared to shoes are worn by somebody who is like someone who is like and wear shoes those shoes will not wear out very fast but people are very heavy their shoes wear out quickly they say oppressed vehicles vehicles which carry a lot of things they attack the tyres wear out quickly because they have a lot of loads vehicles that carry a lot of things vehicles are overloaded the tires were out quickly because of too much friction so weight increases friction let's look at two uses of friction how is friction important number one friction helps vehicles to move on roads without sliding vehicles move or road without sliding so that's our future is important it helps vehicles to move around guard sliding not only vehicles but in the human beings it helps people to move without sliding look at tiles in the bathroom the moment you put soap on tires and you start moving those stains will become slippery and it becomes hard for you to walk or to move on those times you just like because friction has reduced so friction helps vehicles to move on roads without sliding if you did that friction then vehicles will be sliding on roads and they cause accidents and as i said friction does not only help vehicles to move helps people helps bicycles helps with batteries it helps in our motorbikes motor cycles to move without sliding we are guessing vehicles not only vehicles motorcycles bicycles even people walking on foot it happened to move last night number two friction helps when writing friction helps when writing if there's no friction you can't make that move if there was no future i would not be able to dread on this board some future helps candidates helps people right number three friction helps when shuffling cutting tools friction helps when cutting when sharpening cutting tools using a file if you want to make a panda sharp if you want to make a store um a knife sharp maybe you want to cut with a piece of meat and you want to cut an orange and the knife is bland you get the fire and you start shafting it it is able to sharpen because of friction so it helps when sharpening cutting tools then it helps when lighting matchsticks will not be able to light my matchsticks without friction so friction helps people like matchsticks number five it helps in scrubbing saucepans for example if you have steel wire you have sand at home and starts grabbing suspense without friction you will not be able to scrub those suspense because they still work with your slide but because of friction you are able to do that then number 7 it helps vehicles to stop when brakes are applied if we have no friction vehicles will move endlessly and we make accidents or cause accidents so it helps vehicles to stop when brakes are applied not only vehicles but also motorbikes also uh bicycles and so on when the brakes are applied they are able to stop because of friction disadvantages of friction how is friction a new sense force how is friction a nuisance falls how is friction bad all those three words mean the same disadvantages of friction how is friction bad how why is friction called a nuisance force now number one it causes wear and tear as much transmission is good it is also very bad how is it bad it causes wear and tear our shoes tear they wear out machines wear out and they stop working look at the tires of vehicles they wear out and that's why we people keep on changing the tires of their vehicles because they wear out due to friction their friction delays work it makes work to be done at a very slow pace for example if you are using a machine and the machine breaks down because of friction it is delayed one then it does work sometimes work cannot be done by machines because of friction so if he does work it produces unwanted noise you've had those making noise whenever you open a door the hinges over though makes a lot of noise why do they make out of noise it is because of friction then it produces unwanted heat friction produces unwanted heat then it lowers the efficiency of a machine it lowers the efficiency of a machine so machines will be in a position to do very good work but sometimes they would work that way machine is reduced because of friction how does the friction lower the efficiency of a machine it doesn't work or it makes the machine grow up at a very small pace how to increase friction because we need friction we have to increase it one making smooth surfaces rough remember we said we looked at the properties of friction we said friction is greater on rough surfaces meaning that when we want to increase friction we make smooth surfaces rough when small cells are made rough we have increased friction putting treats on vehicle tires putting treads on vehicle tire look at this diagram here these are what you call trips trips are those marks on tyres they are like designs on tire and the soles of our shoes if you look at my shoe look at my shoe look at my shoe these are what you call treats i think these designs here these designs are called tricks and these strings they help to increase friction to prevent people from sliding when they are walking or moving so these are what we call trips trees are not only on soils or shoes but they are also found on car tires also bicycles and motorbikes tires you find their treats so are putting treats on their hotels putting tricks on shoe soles putting treats on shoe solve then putting spikes on sports boots putting spikes on sports boots then putting grips on bicycle handles if you got bicycle handles where you hold there are grips there they are marks where you hold those marks are there to increase friction so these are tricks and we are saying trips help to increase friction treats treats help to increase friction so let's look at how to reduce friction how to reduce friction how to reduce friction one by using rollers by using rollers number two by using ball bearings number three by lubricating moving parts to lubricate simply means to grease or to oil because oil and grease are called lubricants so oil oiling and greasy moving parts is another way of saying lubricating moving parts of a machine then by streamlining moving objects streamlining moving objects to streamline moving objects means you make them sharp at the front and the back they become sharp at the front all that is done to reduce friction then by moving by making rough surfaces smooth by making rough surfaces smooth we can make rough surfaces smooth that is one way of reducing friction by making rough surfaces smooth by by making rough surfaces smooth let's look at example of streamlined objects we have cars aeroplane fish bots ship burns all these are streamlined objects why are they streamlined to reduce friction they can ask you why are airplanes streamlined why are they made sharp why are they pointed at the front like this so this one is a streamlined object like a sphere a spear is also streamlined to reduce friction fish baths are streamlined to reduce friction in air fish are stimulating to reduce friction when swimming in water when airplanes are moving in air they are able to reduce friction because they are streamlined as simple as that so next we look at the machines what is a machine okay so let's look at machines what is the machine remember we've been looking at friction reset friction is a force that proposes movement between objects in contact and the topic of today is simple machines and friction so we've looked at what friction is next look at what a machine is what is a machine a machine is a device that simplifies work a machine is a device a machine [Music] is a device a machine is a device that simplifies work simplifies work a machine is a device that simplifies what a divide that simplifies what i repeat a machine is a device that simplifies work a machine is a device that simply [Music] work how do machines simplify work how do machines simplify what that's a question simply [Music] machines simplify wow so machines can simplify work in three ways one by changing the direction of force by changing [Music] the direction of force by changing the direction of force number two machines can simplify work by reducing the effort needed to do up by reducing the effort by reducing the efforts by reducing the effort needed to go up by reducing the effort needed new work number three how do machines simplify work machines can simplify work by increasing the speed of being one by increasing the steam by increasing the speed of doing work increasing the speed of doing work so that's how machines simplify wow machines can simplify work one by changing the direction of force by reducing the effort needed to do work by increasing the speed of the work so if you had a machine you do work at a very short period of time for example if you are building a house and you need to carry building materials if you have bricks to carry one person is cutting bricks using hands then another one is carrying bricks using a vehicle who will do work faster the one using a vehicle automatically will do work faster because it's using a machine then who will use a lot of energy the one using hands will use a lot of energy to kind of breaks but the one using a vehicle will use less energy because he's using a machine so that's how machines simplify work by changing the direction of force reducing the effort needed to do work then by increasing the speed of doing work next we look at types of machines we have two title machines we have simple machines and complex machines types of machines one we have simple machines simple machine [Applause] then two we have complex machines complex machines also known as complicated machines let's begin by looking at complex machines what are they what are the examples complex machines these are machines made up of many parts and simplify wow these are machines all these are devices this are devices and devices and devices made of manipuls made up of many parts and simplified work these are devices made up of many pads and [Music] simplify work examples of complex machines examples of complex machines examples of complex machines examples of complex machines one we have vehicles vehicles are complex machines number two we have bicycle structures bicycles number three we have tractors number four we have the ship number five we have airplanes airplanes all these are examples of machine no all these are examples of complex machines why are they called complex machines they are made up of many parts and simplify work and the question why are cars why are cars called complex machines they are made up of many parts they are made up of many parts they are made up of many parts and simplified work and simplify [Music] work they are made up of many parts and simplified work then why are cars called machines why are cars called machines why are cars called machines colorful machines because they simplify work why are cars called machines they simplify they simplify what that's why they are called machines next we look at simple machines simple machines simple machines are devices made up of few parts and simplified work simple machines simple machines our devices are devices made up of few parts of medical fitness and simplify work and simplify work as simple as that so remember the topic is simple machines and friction so we are going to look at major simple machine and what is a simple machine a simple machine is a device that is made up of few parts and simplifies work a simple machine is a b rice made up a few packs a simplified one simple machines are devices made up of impacts and simplify work as simple as that then you look at the example of simple machines examples of simple machines [Music] examples of simple machines okay we said simple machines are devices made up of a few parts and simplified work look at examples simple machines a hole wheelbarrow pair of scissors fishing rods staircase and so on why are they called simple machines for example let's have a question here why is a fishing rod why is a fishing rod called a simple machine why is the fishing rod called a simple machine white is a fishing rod called a simple machine it is made up is made up of few parts it is made up of few parts and simplified work and simplify work then why is why is a fishing rod called a machine why is a fishing rod called a machine a fishing rod we go back to the definition of a machine you say the machine is a device that simplifies work so one is a fishing rod called a machine a fishing rod is called a machine because it simplifies what it simplifies wow that's why it's called a machine why is it called a simple machine it's called a simple machine because it is made up of few parts and simplify work then we look at the classes of simple machines we have six classes simple machines classes of simple machine glasses or simple machines glasses of simple machines so simple machines are valued into six classes we have believers leave us as one class then we have inclined flames inclined planes also known as slopes we have pulleys we have pulleys as a glass we have screws we have screws as i trust then we have will and exhale will and also will and number six we have wages we have to call wages we have wages so the six classes of simple machine we have livers inclined plants inclined planes also known as slopes and the uninclined plane is a slanting surface and surface which is slightly is called a slope or an inclined plane we have livers we have pulleys we have screws with an axle then lastly we have wedges those are the six classes of simple machines let's begin by looking at rivers leave us and what is [Music] fulcrum or pivot a leveler is a stiff rod a lever is a steel frog that turns freely that stands freely on a fixed point on a fixed point called debut or frontrunner a liver or liver is as defraud that turns freely on a fixed point called pivot of fulcrum a lever is a stiff rod that turns freely on a fixed point called pivot of our problem let's pass our liver parts of a level let's look at parts of our liver we have the load the effort the pivot the effort arm and the load arm what is the effort the effort is the force you overcome the lord then what is the lord the lord is the weight of the body to be lifted so the weight of the body to be lifted is what we call the weight or the load that's the weight of the body to be lifted then you look at the foot look at the fulcrum or pivot pivots or fulcrum now pivot off fulcrum is the turning point of a machine is the turning point is the turning point of a machine is the turning point so the turning point of a machine is called pivot or fulcrum then we have the lord arm the lord arm the lord arm is the distance between the lord and the effort the lord [Music] is the distance the distance between the lord and the efforts no the distance between the lord and the people is called the lord arm pivot or fulcrum is the distance between the lord and the pivot oh fulcrum that is called the load arm then we have what we call the effort arm the effort arm [Music] effort arm effort arm is the distance the distance between is the distance between the pivot and the effort is that distance is the distance between the people and the effort so that distance between the pivot and the effort is called a front arm the distance between the load and the pivots called load arm then the load is the weight of the to be lifted then the effort is the force used to overcome the load is the force used to overcome the load next look at classes of lemurs classes of livers glasses of levels classes levels we have three classes of levels depending on the position of the load effort and pivots there are three classes of levers depending on the position of the fulcrum load and effort so we have three classes we have [Music] first class lemurs number two [Music] we have second class second class leave us then we have third class levers and b class olympus are named according to the position [Music] classes of believers are named according [Music] the position according to the position [Music] of the load efforts and pivots classes of livers are named according to the position of the lord efforts and people so we have three classes of livers and these three classes believe us the first and third first class second class and third class and this class delivers a name according to the position of a lot that effort and payroll or fulcrum that is how we name classes of livers so in our next lesson we shall look at these classes of livers beginning with first-class viewers otherwise thank you so much for being attentive in my lesson may the almighty god bless you abundantly