Simple machines are the basic moving parts in the complex machines that make our lives easier and more efficient. There are many simple machines around your home, and our lives would be much more difficult without them. Doorknobs, faucets, stairs, knives, forks, hinges, wrenches, drill bits and chisels are all examples of simple machines. We depend on simple machines to increase our ability to increase force. Simple machines can also move things farther or faster than we could by ourselves. Golf clubs, tennis rackets, baseball bats, egg beaters, and gears on a bike or car are necessary simple machines that increase force.
Simple machines include levers, wheel and axles, pulleys, inclined planes, wedges, screws and gears.
Levers – A lever is a bar that pivots on a turning point called a fulcrum while it supports two or more forces located at different points on the bar. There are three classes of levers: Class 1, Class 2 and Class 3.
Wheel and Axle – The wheel and axle is an example of a class 1 lever. The wheel and axle is really a continuous lever rotating around a fulcrum.
Pulley – A pulley is also an example of a lever. It includes a grooved wheel over which a rope, chain or belt passes. A fixed pulley is attached to a support and does not move. A movable pulley is one that is attached to a load or counter force and moves as the load moves.
Inclined Plane – An inclined plane is a sloping surface. It can be used to alter the effort and distance involved in doing work.
Wedge – A wedge is an inclined plane that moves to change the direction of a force.
Screw – A screw is an inclined plane wrapped around a shaft. When a screw is driven into a piece of wood, the screw travels only a short distance, but the slope (thread) travels much farther, increasing the effort of turning and driving the screw with a great deal of power.
Gears – Gears are wheels with teeth. The teeth of one gear fit between the teeth of a second gear. As one gear turns, the second one turns also.
Work is the product of a force moving some distance. Machines do not change the amount of work. However, machines can produce a mechanical advantage which alters the amount of effort applied. The ability of a lever to increase the force applied to a load is called its mechanical advantage. The mechanical advantage of a lever depends upon the distance from the fulcrum to the load and the distance from the fulcrum to the effort.