Giving a dramatic increase in speed at the blades. Each rotation of the large wheel (blue) makes the smaller wheels turn round several times (red), This large wheel meshes with a pair of small gear wheels fitted to the top of the When you crank the handle, you turn the large outer gear wheel at moderate speed. Photo: In an egg whisk, gears help to make light work of mixing in twoĭifferent ways-by increasing speed and changing direction. That's what we'd expect from a pair of gear wheels where one (red) is twice the size and has twice as many teeth as the other (blue). So when we get to point (3), we have twice the speed and half the force that we had at point (1). But the blue bar will work the other way and maybe halve the speed and double the force. The red bar might give us four times the speed and a quarter of the force at point (2). Putting everything together, what do we get? We apply a certain force and speed at point (1). So if we apply a force at point (2), it's magnified by the leverage of the blue bar and we get more force (and less speed) at point (3). Now the blue bar is also a lever, but it's working the other way: like a spanner. As the two bars touch, they must be going at the same speed. That's the red bar, which is just touching the blue bar. If you turn at point (1) instead, the opposite is true: you get more speed and less force at point (2). Then point (1) would turn with less speed and more force. If you can't see this, suppose the red bar were a spanner and you pushed at point (2) to undo a nut at point (1) in the center. The bar connecting points (1) and (2) moves faster and with less force at point (2) because it's working as a lever. Thinking of gears as levers shows exactly how they work. But a wheel is really just a lever, so a pair of wheels that touch is like a pair of levers that touch (bottom). The pair of gear wheels (top) works in exactly the same way as an ordinary pair of wheels the same size that are touching (middle) the only difference is that the gears have teeth cut around the edge to stop them slipping. Gears sound like magic, but they're simply science in action! Look at the diagram here and you'll see exactly how they work. Through 90 degrees and turn the back wheels. The middle of the rear axle of a rear-wheel drive car) uses aĬone-shaped bevel gear to turn the driveshaft's power In a car, for example, the differential (a gearbox in You canĪlso use specially shaped gears to make the power of a machine turn One turns clockwise, the second one must turn counterclockwise. Together, the second one always turns in the opposite direction. (Turn theīlue wheel and the red wheel goes slower but has more force.) Wheel), it turns slower than the first one but with more force. Would make the blue wheel (with 20 teeth) go twice as fast but with halfĪ pair of gears has more teeth than the first one (that is, if it's a larger Looking at ourĭiagram below, turning the red wheel (with 40 teeth) Turns faster than the first one but with less force. So this arrangement means the second wheel Means it's a bigger-sized wheel), the second one has to turn round Gears together and the first one has more teeth than the second one (generally that Power from one gear wheel to another, you can do one of three things: You can have any number of gears connected together and they canīe in different shapes and sizes. Running under the car that ultimately powers the wheels. That takes power from the engine) to the driveshaft In a bicycle, for example, it's gears (with the help of aĬhain) that take power from the pedals to the back wheel. Gears are used for transmitting power from one part of a machine That's simply because the pedal wheel and the back wheel are some distance apart and a chain is the easiest way to link them together. Wheel you pedal with those on the back wheel. Lubricated chain connects together the gears (known as sprockets) on the In a bicycle, the gears don't link by meshing together directly. So the teeth of one wheel lock into the teeth of another that stops them slipping, which means power is transmitted In a car or a motorcycle, the gears "mesh" An opened-up gearbox on show at Think Tank, the science museum in Birmingham, England. Or send the force of a machine off in another direction. They're a simple way to generate more speed or force Gears are helpful in machines of all kinds, not justĬars and cycles. Flick to a different gear and you can go incrediblyįast: you can magically make your wheels turn round much faster than Once you're back on the straight, it's aĭifferent story. Much impossible unless you use the right gear to Have you ever tried pedaling a bicycle up a really steep hill? It's pretty
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