A machine is a device that uses energy to do work.
Tools that have only a few parts are called simple machines. For example, hammer is a simple machine.
In science, work means moving something. To move something we use force. The more force it takes to move an object, the more work is done. The more distance something moves, the more work is done. Whenever you push, pull, turn or lift an object, you use force. The amount of force it takes depends on how heavy the object is. It takes a lot more force to move a big rock than to move a small rock.
There are 6 basic types of simple machines.
An inclined plane is a flat surface with one end higher than the other. This allows for heavy objects to slide up to a higher point rather than be lifted. It is generally easier to slide something than to lift it. Examples include slides and ramps.
A wedge is really just two inclined planes that meet. It has a slanted edge which is sharp. It can be used to cut materials apart and also push things apart. For example, the blade of a knife is a wedge. Your front teeth are also wedges. Wedges cut through things by moving them apart. The narrower the wedge, the easier it is to move things apart.
A screw is an inclined plane wrapped around a rod. Examples of the screw include swivel chairs, jars, lids, and screws. Screws can be used to lift things or to hold them together.
A pulley is a type of simple machine that uses a wheel with a groove in it and a rope. The rope fits into the groove and one end of the rope goes around the load. You pull on the other end. The pulley helps you to move the load or change direction of the force. Some examples of pulleys include cranes, flag poles, and window blinds. Pulleys are also used by old-fashioned water wells.
When multiple pulleys are used together it’s called a block and tackle. Another use of the pulley is with a flat wheel and belts. These kinds of pulleys are often used in cars.
The wheel and axle is another simple machine. It uses a wheel with a rod attached in the middle as an axle to help it to lift or move loads. In some cases, this machine works like a lever to multiply force and in other cases, it is used to move objects easier such as with wheels on a bicycle.
The lever is made up of a straight rigid object like a board or a bar that pivots on a turning point called a fulcrum. Levers make work easier by using leverage which multiplies the force. When you use a lever, you move a smaller force a longer distance in order to lift a load a short distance. Examples of levers include a seesaw, pliers, crowbars, and tweezers.
In summary,
Some machines combine several simple machines. These are called complex machines. For example, a wheelbarrow is a lever with a wheel and axle. A bicycle has wheels and axles, pulleys, and gears. A can opener uses a wedge, a lever, and a gear.
Complex machines make difficult or dangerous tasks easier. Electric mixers mix batter over and over. Cranes help us build buildings. Robots build cars and dig through the rubble. Each of these machines combines simple machines to make work easier.
