How Wheels Help Us (1966)

foreign [Music] how do Wheels help us a wheel rolls and things that roll are easy to move [Music] it's much harder to slide something than to roll it as the barrel slides over the rough cement the boys have to use a lot of strength to move it the barrel is rubbing against the sidewalk at the same time the sidewalk is rubbing against the barrel slowing it down we say it slows down because of friction stop sliding and you reduce the friction now there's almost no sliding so the boys are working against very little friction that's why a rolling object is easier to move but what does this have to do with wheels you don't need wheels for a barrel no but what if you want to move one of the boys here's a better way or is it that's right you need more barrels to move a longer distance of course you'd never really use barrels this way but you might use metal rollers which work much the same way as barrels rollers or barrels are not so good for moving boys wheels are better each wheel turns on an axle between the Turning wheel and the axle there is some friction there's not as much friction between this wheel and axle the roller skate wheel turns easily because it's on ball bearings you can see the bearings when we remove part of the wheel see tiny metal balls between the wheel and axle with these bearings the wheel rolls very easily around the axle ball bearings are also used on a bicycle wheel the wagon doesn't have ball bearings but there's still less friction than if the wagon were dragged over the ground notice that each wheel is free to turn by itself the axle doesn't turn with it but sometimes wheels are fastened to an axle most train wheels are made this way both wheels and Axle turn together these toy wheels are fastened to the axle in the same way see if you turn one wheel the axle and the other wheel turn also this doesn't work so well when you try to make the wheels follow a circle the outside wheel skids because it isn't free to turn a greater amount than the inside wheel now we fix the wheels so that each one can turn about the axle separately this is a better arrangement for following a circle now the outside wheel can move a greater amount than the inside wheel and it doesn't slide remember that the wheels on the wagon are also free to turn separately the wagon can turn around in a small space tractors must also turn in very small circles so the wheels are made so they can turn different amounts what about the wheels on a car yes each one is free to turn a different amount can you think of other uses for a wheel suppose we change the wheel a little by cutting out notches now it's a special kind of wheel a gear The Notches or teeth of the gears they're called can fit between the teeth of another gear so if you turn one you turn the other they turn at the same speed because they're the same size by making one gear smaller than the other with fewer teeth we can make one gear turn faster than the other how can we be sure Mark both gears to give each a starting line now watch the line on the small gear as we turn the large one see the small one turned several times in the time it takes the large one to turn once Gears of different sizes can help us in many ways a hand drill works with gears the hand turns a large gear the large gear drives a small gear connected to the drill the drill turns several times each time the hand goes around once so it's possible to turn the drill very fast when you turn the pedals of a bicycle you're turning another kind of wheel something like a gear sprocket wheel the sprockets or teeth of this wheel fit between the links of a chain the chain moves when you turn the wheel the sprocket wheel with the pedals is much larger than a second sprocket wheel attached to the bicycle wheel so each time your feet go around once the rear wheel turns several times that's one of the reasons you can go so fast on a bike a sewing machine makes use of Wheels driven by a belt instead of by a chain this wheel has raised edges to keep the belt from sliding off there's a lot of friction between the wheel and the belt because the belt presses tightly against the wheel when the belt is moved the wheels move along with it she keeps her fingers away when the motor is on here's a wheel used in another way recognize the round handle of a faucet with the wheel off try turning it on using just your fingers it's pretty hard to do it's much easier with a wheel with the wheel you can apply more Force this boy is applying Force to a wheel on this cart the steering wheel the steering wheel is fastened to a long post connected to the post at the bottom are two rods turning the post moves the rods the other ends of the rods are connected to the front wheels controlling their Direction in this way the steering wheel can be used to control the direction of the cart you've seen some of the ways in which Wheels help us but have you seen all the ways of course not there are many many other uses for Wheels just look around you [Applause] [Music] [Applause] [Music] thank you