How Do Gears Work?

Gears are simple machines that help us increase the force needed to push or pull something. Other simple machines are levers, pulleys, inclined planes, and wheels and axles.

Gears are a part of many machines, like bicycles and cars. A gear is a rotating machine which has teeth (cogs). When they connect to another gear, they transmit torque, which is like a twisting force. When two gears work together, it is called a transmission. Gears are helpful in transmitting power from one part of a machine to another. 

Gears are helpful in three ways. They:

• Increase speed - When a gear with more teeth is connected to a gear with less teeth, the second turns faster, but with less force. This increases speed as the second one is turning faster.
• Increase force - Force is increased if the second wheel has fewer teeth, so it is smaller, and it will turn slower but have more force.
• Change direction - A change of direction occurs because the second gear always turns in the opposite direction of the first gear.

Not all gears are just two wheels with teeth.

• Worm gears have one circular gear which meshes with a screw-like gear. It is useful as it makes the larger wheel turn with more force and also changes the direction of rotation.

• In a rack and pinion gear, the pinion is the gear wheel and it meshes with the rack, which is a long bar with cogs. When steering a car, the steering wheel is connected to a pinion that makes the rack move from side to side, which in turn moves the wheels from left to right.

Other Simple Machines

Gears and other simple machines allow us to be stronger and do a job without using as much force. They can be knives, thumbtacks, hammers, or a ramp. Following are explanations and examples of simple machines.

Levers

Levers make use of a fulcrum, or pivot point, like a seesaw. The farther away you are from the fulcrum, the bigger the force you can produce. There are three classes of levers:

• Class 1 levers have the force applied on the opposite side of the fulcrum, like scissors and pliers.
• Class 2 levers have the fulcrum at one end, like wheelbarrows, nail clippers, and nutcrackers.
• Class 3 levers also have the fulcrum at one end, but the force is applied in the center, like in tweezers and tongs.

Pulleys

Pulleys work by redirecting and increasing the force applied which makes it easier to move a big load.  When the distance is increased, less force is needed, like when you use a screwdriver with a longer handle, you use less force to get the job done.

When you put two or more wheels together, and run a rope around them, you have created a pulley and a great lifting machine. As you add more pulleys, you increase your mechanical advantage. Pulleys can either be fixed, mobile, or a combination of the two. A bull dozer is a good example of a pulley.

Ramp

The simplest example of an inclined plane is the ramp. Even though you cover more ground, the force you need is less.

Other Simple Machines

Sometimes, screws and wedges are included as separate simple machines, but they can be classified as inclined planes. A screw is like a ramp wrapped in a circle. The head of the screw is actually like a wheel or lever. Wedges are two inclined planes together, like a knife, a nail, the tip of a fork, and a door stop.

When wheels and axles were invented over 5000 years ago, it made a huge impact on the amount of work we could do and on transportation. Wheels and axles made it much easier to push a heavy cart or box. On cars and bicycles, the bigger the wheel the faster you can go with the same amount of force that you apply. Examples of wheels, other than the obvious, are wheelbarrows that add a lever to the wheel and axle, and clocks.