School’s out and you just need something fun to do (besides those piling holiday homework!) Hanging out aimlessly is just so passe, not to mention a waste of your brilliant mind. So, what would be a greater thing to do this holiday than learning up a new science concept to satiate the geek within us? XD

A gear is a rotating machine part having cut teeth, or cogs, which mesh with another toothed part in order to transmit motion (torque). Geared devices can change the speed, magnitude, and direction of a power source.

The gear wheel being turned is called the input gear and the the one it drives is called the output gear.Gears with unequal numbers of teeth alter the speed between the input and out put. This is referred to as the Gear Ratio.

As you see from the diagram above, A and B has different number of teeth. Say, A has 10 teeth and B has 30 teeth, the Gear Ratio is 3 to 1 (ratio of the number of teeth of the output gear B to the number of teeth of the input gear A). That means, for every one full revolution of the input gear (A), the output gear only completes 1/3 revolution. This process is called Stepping Down.

Stepping Up

If the input gear has more teeth than the output gear, the ratio will be less than 1, and for every one full revolution of the input gear, the output gear completes more than 1 revolution. This is called Stepping Up.

In essence, you would want to step up if you want to create a fast movement. But note that this gain in speed is counterbalanced with much reduction in power. Often, the output gear of a stepping-up transmission becomes tensed and/or stuck as it does not have sufficient power to do work. Stepping down is then relevant as it gives you more power albeit at a slower rate.

Gears are widely used in today’s world. Example of its application is shown below:

1) Windshield wiper uses motorized gears to move the wiper arms to and fro around its pivot.

2) Bicycle gears are used in mountain bikes to adjust desired output power/speed. Lower gears (stepping-down gears) are used when traveling through an upward sloping terrain as it allows the biker to exert less power to do the same work, making it’s easier to climb the slope. Higher gears (stepping-up gears) are used when you want to whip up your bike speed to take over the biker in front of you.

Must gears always be round in shape? If your answer is yes, then think again.

You can follow the link given after the youtube video to create oddly-shaped gears of your own! That’s another real fun science project to do this holiday.