# Simple machines & Compound machines

## Levers (1st 2nd and 3rd class)

A lever has a bar that rotates at a fixed point called a fulcrum. The force that is applied to the lever is called an input force. The object being lifted by the lever is called the load. The purpose of the lever is to apply a force to move a load. A first class lever is a lever in which the fulcrum is between the input force and the load and the direction of the input force always changes direction on this type of lever and can be used to increase either force or distance of the work. A second class lever is a lever is where the load is between the fulcrum and the input force, like a wheelbarrow. The last type of lever is a third class lever is when the input force is between the fulcrum and the load, like a hammer. Levers reduce the force required to lift the load by increasing the distance in which that force is applied so in order to increase the mechanical advantage of a lever you increase the length of the effort side by moving the fulcrum closer to the load.

## Pulleys (Fixed, movable, block and tackles)

A Pulley is a simple machine with a grooved wheel that holds a rope or cable. An input force is applied to one end of the cable and the object being lifted is called the load.There are many different types of pulleys a fixed pulley is a pulley that is connected to something that does not move, to use it you pull down on the rope to lift the load and the direction of the force changes since the size of the output force is the same as the input force the mechanical advantage is 1. A movable pulley is a pulley that is directly attached to the load, in this type of pulley the direction of the force does not change but the size of the force does the mechanical advantage of movable pulleys is 2 so less force is needed to lift a load. The last type of pulley is actually a system of pulleys, the combination of a fixed and movable pulleys together, the block and tackle and the mechanical advantage of the block and tackle is equivalent to the number of sections of rope in the system.

## Wheel and axles

A wheel and axle is a simple machine that is made up of two round objects that move together. The larger object is the wheel and the smaller is the axle. The mechanical advantage of a wheel and axle is calculated by dividing the radius of the wheel by the radius of the axle so you increase the mechanical advantage of a wheel and axle by increasing the radius of the wheel or decreasing the radius of the axle. Using a wheel and axle makes work easier because when you turn the wheel the axle turns a smaller distance because its smaller resulting in a greater output force than input force.

## Inclined Plane

An inclined plane is a simple machine that has a flat, slanted surface like a ramp. It makes work easier by increasing the distance work is done and decreasing the amount of force required to do the same work,making it easier. The mechanical advantage of the inclined plane is calculated by dividing the length of the inclined plane by the height the load raised. To make work easier by decreasing the input force by putting it over a larger distance

## Wedge

A wedge is a simple machine made of two inclined planes that move, just like an inclined plane a wedge needs a small input force over a large distance making work easier. The mechanical advantage of a wedge is the length of the wedge divided by the largest thickness of the wedge. Examples of wedges would be scissors and ax heads.

## Screw

A screw is an inclined plane that is wrapped around a cylinder. To turn a screw a small force over a long distance is needed and the screw applies a large output force over a short distance. In order to find the mechanical advantage of a screw u need to first unwind the inclined plane and if you compare the length of the inclined plane with its height you can calculate the mechanical advantage the same way you would an inclined plane (length of inclined plane/height load raised)

## Compound Machines

Compound machines are machines that are made up of two or more simple machines for example a can opener which is made up of the wedge, wheel and axle, and second class lever simple machines. The mechanical efficiency (Percent of work input that gets done as work output) of most compound machines is low because compound machines tend to have moving parts meaning more parts are in contact with each other and causes more friction and lowers the output work.