# Force and Machines

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For many years, people have waged an uphill struggle against the forces of gravity and friction. Fortunately, we now have machines of all kinds to help us along the way. In this wikibook, you will explore different types of machines, find out how they work and discover that the use of simple machines to perform great feats is nothing new.

# Get Moving

## Force

Like any other object, a bicycle starts to move only when something pushes or pulls on it. A push or a pull on something is called a force. When you ride a bike, you apply force with your legs to keep the bike moving forward. On level ground, most of your effort goes into pushing the bike forward, but when you come to a hill, you also have to work against gravity. So, when you ride up the hill you have to push your bike up against the force of gravity.

Work is done when a force moves an object through a distance. The distance must be in the direction of the force.

## Friction

Friction is a force that resits the motion of one surfacer past another surface. This force creates a resistance on moving objects and causes them to stop. Wheels or rollers help cut friction between moving, touching surfaces. But you can also use a thick liquid like oil or grease to reduce friction. They are lubricants – substances that reduce friction. Grease forms a smooth layer and makes it easy for an object to slip. Ball bearings are small balls that help cut down on friction inside machines by keeping metal surfaces from rubbing against each other. A bicycle has ball bearings where the wheels are joined to the frame.

However, thanks to friction, the tires do not slip and the bike moves.

## Simple Machines

### Inclined Planes

Inclined Planes are a type of simple machine useful for raising or lowering a load. An example of a inclined plane is a ramp. A inclined plane allows you to exert less force over a longer distance to achieve a given workload. It looks like a flat, slanted surface.

### Lever

Levers are machines consisting of a beam resting on or supported by a point called the fulcrum. Levers allow a large force to be distributed over a small area at one end by exerting a smaller force over a larger area on the other. There are three classes of levers.

• Class 1 - the fulcrum is in the center, between the effort, on one side, and the resistance (load), on the other. Examples include scissors.
• Class 2 - the resistance is in the middle, the effort on one side, and the fulcrum on the other. Examples include a wheelbarrow and bottle opener.
• Class 3 - effort is in the middle, fulcrum is one side, and the resistance is on the other. Examples include tweezers or the human jaw.

# Everyday Machines

## Gears

Gears may be defined as any toothed member designed to transmit motion or power from one shaft to another preferably if the distance between the two shafts is small. It is a positive and smooth drive.

Gears are generally used for one of four different reasons:

1. To reverse the direction of rotation.
2. To increase or decrease the speed of rotation.
3. To move rotational motion to a different axis.
4. To keep the rotation of two axes synchronized.

## Bike Design

The Bike of your dreams