A machine is a tool used to make work easier. It can do so by changing the direction of a force, increasing the distance or speed of a force, transferring a force from one place to another or increasing the magnitude of a force. Machines are everywhere in our daily lives and make peoples' lives today much simpler, but no matter how complex a machine may appear, it is simply a combination of the six simple machines.
Inclined Plane: Easy Lifting
An inclined plane is simply an even, sloping surface. One common example of an inclined plane is a ramp. Lifting heavy items onto a higher surface is much easier if you just slide the item up a ramp.
Wedge: Splitting and Separating
A wedge is a modification of an inclined plane. Wedges are usually used as either separating or holding devices. An axe blade is one example of a wedge — you can make a small crack much larger by using an axe blade. Another example is a door stop.
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Screw: Fastening and Moving
A screw is another modified inclined wedge. This can be hard to visualize, but just think of a screw as an inclined plane wrapped around a cylinder.
Lever: Multiplying Force
Any tool that is used to help pry something loose is a lever. A lever is an arm that pivots against a fulcrum. An example is the claw end of a hammer, being used to pry nails out of wood. Another example is a seesaw.
Wheel and Axle: Rolling
A wheel and axle consist of a large wheel secured to a smaller shaft, here referred to as an axle. If the wheel turns but the axle remains stationary, it isn't a true wheel-and-axle machine. Wheels and axles are everywhere — think of a childhood play wagon for one example of a wheel and axle in motion.
Pulley: Hoisting Heavy Loads
A pulley is a machine similar to a wheel and axle, but where rope is turned rather than the axle. As the wheel rotates, the cord is moved in either direction. This can help lift or move objects. A flagpole is one example of a pulley.
Scissors: Making the Cut
As a machine, a pair of scissors seems pretty simple, though it's actually a complex machine. A scissors combines two levers with the cutting action of the wedge. The levers multiply the force on the object to be cut, making it easier to use and more effective than a knife.
Hand Truck: Mover's Friend
Like the scissors, a two-wheeled hand truck is also a complex machine. The lever and the wheel and axle partner to make a machine that lets you lift and move furniture, appliances and other objects too awkward or heavy to carry by hand.
Automobile: Many Machines
It should be no surprise that an automobile with a gasoline engine is a complex machine, made of thousands of simple machines. Inside the engine, each rocker arm that operates the many valves is a lever. The timing belt is a type of pulley, and the car rides on four wheels mounted to two axles.