As we’ve seen earlier, simple machines form the basis of mechanical physics. All complex machines are actually made of a number of simple machines working in tandem with each other. Simple machines help make our work easier. Given their importance in the world of Physics, anyone interested in the STEM subjects must have a basic knowledge of what constitutes simple machines.
Simple Machines are divided into the following six types-
- Wheel and axle
- Inclined plane
All six of the simple machines have been in use for thousands of years. Interestingly, the physics behind several of them were quantified by Archimedes.
So let us study these six types of simple machines in a little more detail-
Archimedes famously said about the lever-
“Give me a lever and a place to stand, and I’ll move the world.”
That, according to him, was the unparalleled power of the lever.
A lever is a rigid bar that is free to pivot, or rotate, around a fixed point called the fulcrum. Applying a force to one end of the rigid bar causes it to pivot about the fulcrum, resulting in a magnification of the force at another point along the bar. A crowbar, scissors, knife, seesaw are examples of lever.
A pulley consists of a wheel with a groove along its circumference, and a rope that is placed inside the groove of the wheel. It uses the principle of applying force over a longer distance, and also the tension in the rope or cable, to amplify the magnitude of the applied force.
The drive element of a pulley system can be a rope, cable, belt, or chain that runs over the pulley inside the groove.
Pulleys can be of many types- fixed pulley, movable pulley, compound pulley.
Pulleys are used on ships to raise and lower sails, in industry to raise and lower heavy cargo, or on cranes for use in moving heavy construction equipment. Elevators also use pulleys to move the car up and down from floor to floor.
Wheel and Axle-
The wheel is considered the most important invention in the history of mankind. And the introduction of the axle to the wheel changed the course of world history. An axle is a rod or pole centred in the wheel in such a way that it allows the wheel to turn around it. The wheel and axle rotate together and transfer force from one to the other.
Sometimes, there may be two wheels attached to both ends of the axle.
Gears are a form of the wheel and axle. An electric motor, electric fan, car, bicycle, a Ferris wheel are all examples of uses of wheel and axle.
An inclined plane does not have any moving parts. It is simply a surface with an even slope. Sliding a heavy load over the slope makes it easier for us to move that load to a higher or lower surface, than if we tried to just lift the load directly upwards. According to historical evidence, ancient Egyptians used inclined planes to carry heavy stones to build pyramids.
The most common example of an inclined plane is a ramp used in houses and public spaces to move wheelchairs or trolleys loaded with shopping.
A wedge is technically an inclined plane or two inclined planes put together to form a pointed triangle that moves to exert a force along the lengths of the sides. Axes, knives, and chisels are all wedges.
The longer and thinner a wedge is, i.e. the sharper it is, the more work it does with little effort.
Wedges have been used by man for millions of years. The earliest tools used by man, such as sharp stones used as spears to hunt and cut trees, were forms of wedges. Modern cars, bullet trains, speed boats and jets also use the concept of wedges. All these have wedge-shaped pointed noses that help them to cut through air and water.
A screw is simply an inclined plane wrapped around a cylindrical shaft. The inclined plane is in the form of helical grooves or ridges called threads that wrap around the cylindrical shaft on the outside.
Screws are of utmost importance in construction as they can hold things together. Additionally, they can be used to lift very heavy objects and tighten things. Corkscrews, taps, light bulbs, bottle caps all make use of the concept of screws to work.
A drill bit becomes a powerful tool that can drill holes in hard materials like metal and stones when attached to an electric drill machine.