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Throughout history, people have developed several simple machines to make work easier. The best known of these are known as the “six simple machines”: axle, lever, ramp, pulley, screw, and wedge, although according to the Encyclopædia Britannica, the last three are really just extensions or combinations of the first three.
According to Boston University, since work is defined as the force acting on an object in the direction of motion, a machine can make work easier by doing one or more of the following:
Simple machines are devices with no or few moving parts that make work easier. According to the University of Colorado at Boulder, many of today’s complex instruments are simply combinations of half a dozen simple mechanisms or more complex shapes. For example, we can attach a long handle to an axle to make a winch, or use a pulley to pull a load up a slope. As simple as these machines may seem, they continue to give us the means to do many things that we would never have done without them.
The wheel is considered one of the most important inventions in world history. “Before the invention of the wheel in 3500 B.C. people were severely limited in how much and how far they could carry things overland,” Live Science previously reported. Wheeled carts made it easier to transport goods to and from the market and saved people from having to travel long distances, thus facilitating agriculture and trade.
Wheels greatly reduce the friction that occurs when an object moves across a surface. According to the University of Tennessee, “If you put a file cabinet on a small cart with wheels, you can greatly reduce the effort required to move the file cabinet at a constant speed.”
In his book Ancient Science: Prehistory – 500 AD. e.” Charlie Samuels writes: “In some parts of the world, heavy objects such as rocks and ships were moved with log rollers. When an object moves forward, the roller is removed from the back and replaced by the front.” This was the first step in the development of the wheel.
However, the biggest innovation was the addition of the wheel to the axle. The wheels may be attached to an axle supported by bearings, or may be free to rotate around the axle. This led to the development of mounds, wagons and chariots. According to Samuels, archaeologists use the development of a spinning wheel as a sign of a relatively advanced civilization. The earliest evidence of wheels mounted on an axle dates back to the Sumerians around 3200 BC. The Chinese independently invented the wheel in 2800 BC.
In addition to reducing friction, the axle acts as a force multiplier. If a wheel is attached to an axle and a force is used to turn the wheel, the rotating force or torque on the axle is much greater than the force acting on the rim. Alternatively, a long handle can be attached to the rod for a similar effect.
All other five machines help people increase and/or change the force applied to objects. Janet L. Kolodner and her co-authors write in their book Moving Large Objects: “Machines provide a mechanical advantage to help move objects. Mechanical advantage is the relationship between strength and distance trade-off.” by increasing the input forces we will be ignoring friction because in most cases the friction is very small compared to the input and output forces involved.
When a force is applied at a distance, it does work. Mathematically, this is expressed as W = F × D. For example, in order to lift an object, we must do work to overcome gravity and lift the object up. To lift an object twice as heavy, it takes twice as much work to lift the same distance. According to Auburn University, it takes twice as much work to lift the same object twice the distance. As the math shows, the main advantage of machines is that they allow us to do the same amount of work with less force over a greater distance.
“Give me a lever and a point of support and I will move the world,” this boastful statement is attributed to Archimedes, a Greek philosopher, mathematician and inventor who lived in the third century AD. While this may be an exaggeration, it does express the power of leverage, at least figuratively, to move the world.
The genius of Archimedes was that he realized that levers could be used to exchange force and distance to get the same volume or work done. According to NYU’s fictional book Archimedes in the 21st Century by Chris Rorres, his law of leverage states that “magnitude is in equilibrium over a distance inversely proportional to weight”.
A lever consists of a long beam and a fulcrum or hinge. The mechanical advantage of a lever depends on the ratio of the lengths of the beams on either side of the fulcrum.
For example, let’s say we want to lift 100 pounds. (45 kg) weight 2 feet (61 cm) above ground. We can apply 100 pounds. For a force acting on a weight in an upward direction over a distance of 2 feet, we are doing 200 lb-ft (271 Nm) of work. However, if we use a 30 ft (9 m) long lever with one end under the load, and place a fulcrum 1 ft (30.5 cm) under the beam 10 ft (3 m) from the load, we get just the other end. pushed down with 50 pounds. (23 kg) strength for lifting heavy objects. However, we had to lower the end of the arm 4 feet (1.2 m) to raise the weight 2 feet. We compromised by doubling the distance the lever had to move, but halving the effort needed to do the same amount of work.
A ramp is simply a flat surface raised at an angle like a ramp. According to Bob Williams, professor of mechanical engineering at Ohio University’s Lass School of Engineering and Technology, ramps are a way to lift loads that are too heavy to lift straight up. The angle (steepness of the slope) determines how much force is needed to lift the load. The steeper the slope, the more effort required. This means that if we lift 100 pounds. By adding 2 feet of weight, rolling it down a 4-foot slope, we halve the required force and double the distance it has to travel. If we were to use an 8 foot (2.4 m) high ramp, we could reduce the required force to 25 pounds. (11.3 kg).
If we want to lift the same 100 pounds. With the rope load, we can attach the pulley to the beam above the load. So we can pull the rope down instead of up, but it still requires 100 pounds. force. However, if we were to use two pulleys – one attached to the top beam and the other to the load – we would attach one end of the rope to the beam, pass it through the pulley on the load and through the pulleys to the lintels, we only need 50 pounds. to pull the rope. Lifting force, although we need to pull the rope 4 feet to lift the weight 2 feet. Again, we trade an increase in distance for a decrease in power.
If we want to use less force over a longer distance, we can use a block. According to the University of South Carolina course materials, “a pulley block is a combination of pulleys that reduces the force required to lift something. The trade-off is that the block pulley needs a longer rope to travel the same distance.”
Despite their simplicity, pulleys find use in the most advanced new machines. For example, the Hangprinter, a 3D printer that can create furniture-sized objects, uses a system of wires and computer-controlled pulleys attached to walls, floors, and ceilings.
“A screw is essentially a long inclined plane wrapped around an axis, so its mechanical advantage can be studied in the same way as tilt,” says Georgia State University. Many devices use a screw to apply a force much greater than the force used to turn the screw. Such devices include locksmith vise and lug nuts on car wheels. They derive mechanical advantage not only from the propeller itself, but in many cases also from the leverage of the long handle used to turn the propeller.
According to the New Mexico Institute of Mining and Technology, “Wedges are moving inclined planes that move under the load to lift, or into the load to separate or separate.” have a greater mechanical advantage, but the wedges do something else: the main function of the wedge is to redirect the input force. For example, if we want to split a log, we can use a sledgehammer to drive a wedge hard into the end of the log, and the wedge will redirect that force outward, causing the log to split. Another example is the door stop, the force with which it is pushed under the edge of the door is transmitted downward, creating friction that prevents it from sliding on the floor.
John H. Lienhard, professor emeritus of mechanical engineering and history at the University of Houston, is “revisiting the invention of the wheel.” Visit the Center for Science and Industry in Columbus, Ohio for an interactive explanation of simple mechanisms. Six simple machines are also illustrated on the HyperPhysics website by Georgia State University.
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Post time: May-31-2023