What Are the 6 Simple Machines?
Simple Machines in Everyday Life.
By Joan Whetzel
There six types of simple machines, some with moving parts, some without. They provide mechanical advantage, meaning they supply that extra force needed to perform certain jobs, the type of force that a person couldn't perform or doesn't have on his or her own. The six simple machines - the lever, wheel and axle, inclined plane, wedge, pulley, and the screw - help the user push, pull or lift items they otherwise couldn't. Some make it easier to change which direction or the distance that an object needs to move or travel.
What Is a Lever?
Levers apply both a pushing and a pulling force, using a fulcrum as a pivot point or an axis between the pushing and pulling forces. There are three classes of levers. The first class leave has the fulcrum in the middle like a teeter totter or scissors. The fulcrum of the second class lever is at the far end of the bar or tool, such as with the hammer, shovel, pry bar, wheelbarrow, or bottle opener. The fulcrum is at the near end of a third class lever such as the human forearm or a fishing pole.
What Is a Wheel and Axle?
Wheels spin around a central axle. They allow objects to be lifted with less difficulty. The lifting force moves objects upward - with a pulley or flagpole for instance - or in a horizontal direction, which makes moving objects over a distance much easier than carrying them by hand. Examples, are cars, bicycles, wheelchairs, roller skates, and dollies. Other examples of wheel and axles are the doorknob and pizza cutter. The doorknob's force consists in changing the direction of the door latch so that the door can be opened or closed. The pizza cutter is uses the wheel and axle to move the blade along, but the force is more like a wedge that forces a space between the slices of pizza.
What Is a Pulley?
Pulleys use a rope, belt or chain wrapped around a grooved wheel to exert an lifting force. They allow heavy objects to be lifted straight upward with less effort and energy needed by the person on the other end of the rope, belt or chain. There are two types of pulleys - a single, fixed pulley and a multiple pulley. An example of a single, fixed pulley is the flagpole pulley. The flag, or other object being lifted, is not all that heavy. However, like the flag, the item needs to be lifted a great distance, like hoisting that flag up a 100 foot flagpole. The person raising the flag couldn't climb the flagpole to hang the flag, so the single, fixed pulley does the work for him or her. The multiple, or compound pulley, allows the rope, belt or chain to make several loops around multiple pulleys in order to lift heavy objects. The weight of the heavy object is distributed over the pulley system so less effort is required by each pulley. Cranes are an excellent example of the compound pulley.
What Is an Inclined Plane?
An inclined plane is a sloped surface that allows objects to be moved upward at an angle with less effort than it would take to lift them straight upward. The difference between lifting an object using a pulley (straight up) and lifting the object using an inclined plane is that the inclined plane requires a longer distance, which means a larger space allocation to accommodate it. Examples of inclined planes include, freeway entrance and exit ramps, driveways, wheelchair ramps, and even staircases. Though the staircase isn't a flat, slanted surface, it's risers work on the same principle; they gradually progress upward in a slanted direction.
What Is a Wedge?
A wedge frequently has the same shape as an inclined plane, or it may be a simple flat surface at an angle. A wedge either uses force to lift objects (i.e. a shovel), pries two objects apart (e.g. pry bar, axe, knife, chisel), or prevents things from moving, like rubber doorstops holding a door open or shims leveling a window or door and preventing them from sagging.
What Is a Screw?
Screws use a twisting force - torque - to hold two things together. They are shaped like an inclined plane twisted around an interior column, like a spiral staircase. A pushing force is required to insert a screw whereas a pulling force removes the screw. The wider the spacing on the screw's threads, the more force it takes to turn the screw. Tighter screw threads require less force, but a lot more turning is needed to turn the screw. Examples of a screw includes, corkscrews, a screw, drill bits, electric drill motors, and the base of a light bulb.
Examples of simple machines are all around us. We use them in everyday life for all kinds of jobs.
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