Simple Machines

Simple machines help us in everyday tasks such as opening a door, getting to school, or even washing your clothes. A simple machine is a device that either multiplies or redirects force. There lies a difference between simple and compound machines. Compound machines are just two or more simple machines working together. Mechanical advantage is the ratio of the resistance force to the effort force and may be calculated using either force or distance. There are six types of simple machines. We’ll talk about three of them; the inclined plane, the lever, the pulley.

There are three different classes of levers. A class-1 lever has its fulcrum located between the load and the effort. The direction of force is changed with this type of lever. Scissors, a crowbar, and pliers are all examples of class-1 levers. When the fulcrum is centered between the load and the effort, the mechanical advantage is 1. When the fulcrum is closer to the load, the effort required increases. On the other hand, if the fulcrum is closer to the effort, less effort is needed to lift the same load. In a class-2 lever, fulcrum is at one end, the effort is at the other end, and the load is in the middle. With this kind of lever, the direction of effort is not changed. Examples of class-2 levers include screwdrivers, catapults, staplers, and wheelbarrows. The mechanical advantage is still the ratio of the effort arm to the resistance arm. With a class-3 lever, the effort force is applied between the fulcrum and the resistance force. In a third-class lever the effort and resistance both move in the same direction. Class-3 levers always decrease the output force, but gain in terms of the distance and speed with which the resistance moves. Examples of third-class levers include tweezers, baseball bats, and hockey sticks. A third-class lever does not change the direction of force; third-class levers always produce a gain in speed and distance and a corresponding decrease in force.

An inclined plane is a sloping surface. An inclined plane may slope at any angle between the horizontal and vertical. The inclined plane makes it easier to move a weight from a lower elevation to a higher elevation. Ramps, sloping roads, chisels, hatchets, plows, air hammers, and carpenter’s planes are examples of inclined planes. The inclined plane produces a mechanical advantage, making it feel like it is easier to move an object between surfaces of different elevation, it does so by increasing the distance through which the force must move.

A pulley consists of a grooved wheel that turns freely in a frame. A pulley can be used to simply change the direction of a force or to gain a mechanical advantage. Examples of pulleys include a basketball lift, a crane, an engine, window blinds, forklifts, chain fans, and a hose crank. A fixed pulley changes the direction of a force; however, it does not create mechanical advantage. A fixed pulley takes advantage of gravity instead of fighting against it while lifting an object. A single moveable pulley creates mechanical advantage; however, it does not change the direction of force.