Category Science

Pulleys are wheels with grooves through which a rope can run. It is much easier to pull something down than to lift it up, as you can use your body weight to help. A pulley enables a downward force to be converted into an upward force. Lifts often use this principle by employing a counterweight. The dropping down of the lift causes the counterweight to rise. Then the dropping of the counterweight helps the lift to go up again.

One wheel

If you have a single wheel and a rope, a pulley helps you reverse the direction of your lifting force. So, you pull the rope down to lift the weight up. If you want to lift something that weighs 100kg, you have to pull down with a force equivalent to 100kg, which is 1000N (newtons). If you want to raise the weight 1m into the air, you have to pull the loose end of the rope a total distance of 1m at the other end.

Two wheels

Now if you add more wheels, and loop the rope around them, you can reduce the effort you need to lift the weight. Suppose you have two wheels and a rope looped around them, The 100kg mass (1000 newton weight) is now effectively supported by two sections of the same rope (the two strands) instead of just one (ignoring the loose end of the rope you’re pulling with), and this means you can lift it by pulling with a force of just 500 newtons—half as much! That’s why we say a pulley with two wheels, and the rope wrapped around it this way, gives a mechanical advantage (ME) of two.

Mechanical advantage is a measurement of how much a simple machine multiples a force. The bigger the mechanical advantage, the less force you need, but the greater the distance you have to use that force. The weight rises 1m, but now we have to pull the loose end of the rope twice as far (2m). How come? To make the weight rise 1m, you have to make the two sections of rope supporting it rise by 1m each. To do that, you have to pull the loose end of the rope 2m. Notices that we can also figure out the mechanical advantage by dividing the distance we have to pull the rope by the distance the weight moves.

Picture Credit : Google

An electronic circuit is made up of a number of components linked together to form a circuit through which electricity flows. Components are devices that have different jobs within the circuit. They may be fixed in position on a circuit board. Electronic components can be made so tiny that thousands of them will fit into a chip a fraction of the size of a postage stamp.

You may have heard the term chip, especially when the subject of computer hardware comes up. A chip is a tiny piece of silicon, usually around one centimeter square. A chip may be a single transistor (a piece of silicon that amplifies electrical signals or serves as an on/off switch in computer applications). It can also be an integrated circuit composed of many interconnected transistors. Chips are encapsulated in a hermetically sealed plastic or ceramic enclosure called a package. Sometimes people refer to the whole package as a chip, but the chip is actually inside the package.

There are two basic types of integrated circuit — monolithic and hybrid. Monolithic ICs include the entire circuit on a single silicon chip. They can range in complexity from just a few transistors to millions of transistors on a computer microprocessor chip. A hybrid IC has a circuit with several chips enclosed in a single package. The chips in a hybrid IC may be a combination of transistors, resistors, capacitors and monolithic IC chips.

A printed circuit board, or PCB, holds an electronic circuit together. The completed PCB with components attached is a printed circuit board assembly, or PCBA. A multilayer PCB may have as many as 10 stacked PCBs. Electroplated copper conductors passing through holes called vias connect the individual PCBs, which forms a three-dimensional electronic circuit.

The most important elements in an electronic circuit are the transistors. Diodes are tiny chips of silicon that act as valves to allow current flow in only one direction. Other electronic components are passive elements like resistors and capacitors. Resistors offer a specified amount of resistance to current, and capacitors store electric charge. The third basic passive circuit element is the inductor, which stores energy in the form of a magnetic field. Microelectronic circuits very rarely use inductors, but they are common in larger power circuits.

Most circuits are designed using computer-aided design programs, or CAD. Many of the circuits used in digital computers are extremely complex and use millions of transistors, so CADs are the only practical way to design them. The circuit designer starts with a general specification for the functioning of the circuit, and the CAD program lays out the complex pattern of interconnections.

The etching of the metal interconnection pattern on a PCB or IC chip uses an etch-resistant masking layer to define the circuit pattern. The exposed metal is etched away, leaving the pattern of connecting metal between components.

Strictly speaking, a wheel on its own is not very useful, but a wheel on an axle is the basis of a huge number of machines. A wheel can be used to magnify a force. A steering wheel, for example, has a force applied to the outer edge, which moves a much longer distance than the centre (axle). The axle moves a much shorter distance and therefore exerts a greater force. When a force is applied to the axle, a wheel can be used to magnify distance, which is what happens in wheeled vehicles. A force applied to the axle moves a much greater distance at the outer edge of the wheels. Finally, a wheel can be used to change the direction of a force. Wheels convert the circular motion of the axle into the forward motion of the vehicle.

This simple machine involves two circular objects — a larger disc and a smaller cylinder, both joined at the centre. The larger disc is called the wheel, and the smaller cylindrical object or rod is referred to as the axle. Sometimes, there may be two wheels attached to both ends of the axle. A wheel alone or an axle alone is not a simple machine. They need to be joined to be called a simple machine.

If you look closely at how a wheel and axle works, you will notice that it is a kind of class one lever. Here, an action on the axle (turning the axle) will cause an output at the other end (wheel turns too). The fulcrum is where the axle meets the wheel. The Wheel and axle work in two basic ways.

Force applied to wheel:

Let us take a screwdriver for instance. If you apply a force to the wheel (the handle), the wheel spins and multiplies the effort to make the output force of the axle (shaft) greater.

A simple door knob is another great example of the wheel and axle. The locking mechanism of the door knob is inside of the door and can only be controlled by the knob. Since it will be difficult turning the axle to open the door, we can turn the wheel instead and that does that job for us.

Force applied to axle:

Now let us also consider a windmill. If you apply a force to the axle, it will multiply the force to the wheel (blades) and result in a greater distance covered. It is because the wheel is larger than the axle and covers more area. A ceiling fan works in a similar way. As the axle turns, it powers the larger wheel (fan blades) to cause the desired output.

The Wheel and axle are perfect for turning turbines and fans; they are also used in automobiles. For example, when you turn the steering wheel of a car, your effort is multiplied by the axle and results in more turns of the car wheels.

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A screw is really an inclined plane wrapped around a cone or cylinder. It works on the opposite principle to a staircase. This time, by lengthening the distance travelled in the circular motion of the screw, the forward force (as the screw moves into the wood or metal) is magnified.

Screws are one kind of simple machines. They have a corkscrew-shaped ridge, known as a thread, wrapped around a cylinder. The head is specially shaped to allow a screwdriver or wrench to grip the screw when driving it in.

The most common uses of screws are to hold objects together — such as wood — and to position objects. Often screws have a head on one end of the screw that allows it to be turned. The head is usually larger than the body of the screw. The cylindrical portion of the screw from the underside of the head to the tip is called the shank. Bolts are a type of screw that usually is designed to work with a nut or another threaded fastener.

Historians do not know who invented the screw. Although it seems to have been invented only in the last few thousand years. The first known use of a screw was as part of the screw pump of Sennacherib, King of Assyria, for the water systems at the Hanging Gardens of Babylon and Nineveh in the 7th century BC.

Around 250 BC, the Greek inventor Archimedes made a screw pump. Archimedes’ machine had a revolving screw-shaped blade inside a cylinder. The blade was turned by hand. This type of machine is called the Archimedes screw. It is still used today for pumping liquids and other materials like coal and grain. By the 1st century BC, wooden screws were commonly used throughout the Mediterranean world in devices such as oil and wine presses.

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There are three different kinds of lever, depending on where the force applied and the loads are in relation to each other. A lever is a rod that can turn on a pivot, or fulcrum.

Levers have four very important parts — the bar or beam, the fulcrum (the pivot or the turning point), effort (or force) and the load. The beam is simply a long plank. It may be wood, metal or any durable material. The beam rests on a fulcrum (a point on the bar creating a pivot).

When you push down one end of a lever, you apply a force (input) to it. The lever pivots on the fulcrum, and produces an output (lift a load) by exerting an output force on the load. A lever makes work easier by both increasing your input force and changing the direction of your input force.

The parts of the lever are not always in the same arrangement. The load, fulcrum, and effort may be at different places on the plank.

Class One Lever

In this class, the Fulcrum is between the Effort and the Load. The mechanical advantage is more if the Load is closer to the fulcrum. Examples of Class One Levers include seesaws, boat oars and crowbar.

Class Two Lever

In this class, the Load is between the Effort and the Fulcrum. The mechanical advantage is more if the load is closer to the fulcrum. Examples of Class Two Levers include wheelbarrows.

Class Three Lever

In this class, the Effort is between the Load and the Fulcrum. The mechanical advantage is more if the effort is closer to the load. An example of Class Three Lever is a garden shovel.

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A slope, or inclined plane, makes work easier because the force needed to move a load is spread out over a longer distance. The amount of work needed to move an object from one point to another does not change, but as the distance is lengthened, less force is needed.

An inclined plane, also known as a ramp, is a flat supporting surface tilted at an angle, with one end higher than the other, used as an aid for raising or lowering a load. The inclined plane is one of the six classical simple machines defined by Renaissance scientists. Inclined planes are widely used to move heavy loads over vertical obstacles; examples vary from a ramp used to load goods into a truck, to a person walking up a pedestrian ramp, to an automobile or railroad train climbing a grade.

Moving an object up an inclined plane requires less force than lifting it straight up, at a cost of an increase in the distance moved. The mechanical advantage of an inclined plane, the factor by which the force is reduced, is equal to the ratio of the length of the sloped surface to the height it spans. Due to conservation of energy, the same amount of mechanical energy (work) is required to lift a given object by a given vertical distance, disregarding losses from friction, but the inclined plane allows the same work to be done with a smaller force exerted over a greater distance.

The angle of friction, also sometimes called the angle of repose, is the maximum angle at which a load can rest motionless on an inclined plane due to friction, without sliding down. This angle is equal to the arctangent of the coefficient of static friction between the surfaces.

Two other simple machines are often considered to be derived from the inclined plane. The wedge can be considered a moving inclined plane or two inclined planes connected at the base. The screw consists of a narrow inclined plane wrapped around a cylinder.

The term may also refer to a specific implementation; a straight ramp cut into a steep hillside for transporting goods up and down the hill. It may include cars on rails or pulled up by a cable system; a funicular or cable railway, such as the Johnstown Inclined Plane.