# engineering topics – sorted

2014.8.4 That’s engineering

• acceleration – the rate of change of velocity. length/time¬≤ or metre/second¬≤. To accelerate an object is to increase its velocity over a period of time.
• adhesive – a compound that adheres or bonds two items together. A mixture of ingredients (typically polymers) dissolved in a solvent. Glues and rubber cements are members of the drying adhesive family. As the solvent evaporates, the adhesive hardens. Depending on the chemical composition of the adhesive, they will adhere to different materials to greater or lesser degrees. These adhesives are typically weak and are used for household applications.
• Aerodynamics – topics included are: Newton’s basic equations of motion; the motion of a free falling object, that neglects the effects of aerodynamics; the terminal velocity of a falling object subject to both weight and air resistance; the three forces (lift, drag, and weight) that act on a glider; and finally, the four forces that act on a powered airplane. Because aerodynamics involves both the motion of the object and the reaction of the air, there are several pages devoted to basic gas properties and how those properties change through the atmosphere.
• aerodynamics – When a golf ball is hit, the impact, which lasts less than a millisecond, determines the ball‚Äôs velocity, launch angle and spin rate, all of which influence its trajectory (and its behavior when it hits the ground). A ball moving through air experiences two major aerodynamic forces, lift and drag. Dimpled balls fly farther than non-dimpled balls due to the combination of these two effects.
• Aerodynamics: used in airplane design. Forces acting on a flying object are: lift, gravity, thrust, drag. Lift is produced through Bernoulli’s Principle and angle of attack. Thrust may be generated by a propeller or a jet. Drag is the result of friction between the flying object and the air.
• air resistance – air pushing on a moving object which slows it down.
• alloy – a uniform mixture made up of two or more chemical elements, at least one is a metal. An alloy has properties different from the metals it is made of. Most alloys are made by melting the metals, mixing them while they are liquid to form a solution, then leaving them to cool and turn solid again.
• alternating current (AC) – an electrical current where the magnitude and direction of the current varies cyclically, as opposed to direct current, where the direction of the current stays constant.
• anaerobic – does not need oxygen
• Apatite – a group of phosphate minerals. It is one of a few minerals produced and used by biological micro-environmental systems. Hydroxyapatite is the main component of tooth enamel and bone mineral.
• apron
• atmospheric pressure: This is also the pressure caused by air, but usually thought of as the normal value or standard value of 14.7 pounds per square inch. The atmospheric pressure at the place where we are on the face of the earth is usually less than this because we are above sea level, and hence have less “weight” pushing down on us. Again, used with the same activities as air pressure.
• auger
• automation – the printing press automates the process of inking the reverse text, pressing it against the paper, and advancing the paper to repeat the process for the next copy of this page.
• backspin – in almost every shot due to the golf club’s loft (i.e. angle between the clubface and a vertical plane). A spinning ball deforms the flow of air around it similar to an airplane wing. A backspinning ball experiences an upward force which makes it fly higher and longer than a ball without spin would.
• Bernoulli’s Principle – in fluid flow, an increase in velocity occurs simultaneously with decrease in pressure.
• Bernoulli‚Äôs Equation
• bit
• blueprints
• boom
• bowl
• bucket
• casting – for making decorative metal buttons
• catalyst – A substance that triggers or speeds up a chemical reaction without itself being affected.
• cellular technology – 2G, 3G, 4G
• center of gravity – the point where an object can be balanced perfectly by a sharp point holding it up under the object. It is the center of mass acting in a gravitational field.
• centripetal force – the force pulling an object toward the center of a circular path as the object goes around the circle. An object can travel in a circle only if there is a centripetal force on it. For an object at the end of a rope, the centripetal force is the tension of the rope and acts towards whatever the rope is anchored to.
• charge-coupled device (CCD) – an integrated circuit containing an array of linked, or coupled, capacitors. Under the control of an external circuit, each capacitor can transfer its electric charge to one or other of its neighbours.
• chemical reaction – a process involving one, two or more substances (called reactants), characterized by a chemical change and yielding one or more product(s) which are different from the reactants.
• chisel – a tool for carving and/or cutting a hard material such as wood or stone or metals. A chisel, typically made of hardened or tempered steel, consists of a sharpened end (called the blade) attached to a straight handle. The user forces the chisel, into the material to cut the material. The driving force may be manually applied, or in some cases using a mallet or hammer.
• Coaxial rotors – uses a pair of helicopter rotors mounted one above the other to produce both lift and thrust. Sikorsky‚Äôs high speed technology demonstrator the X2 uses this design as well as many Russian helicopters. To neutralize the torque, the rotors spin in opposite directions creating equal and opposite torques that cancel each other and eliminate the need for a tail rotor. Yaw control is achieved by increasing the collective pitch of one rotor and decreasing the collective pitch on the other.
• color depends on the gas – Neon (Ne) (gas) tube generally only Illuminates red, orange, and amber. Most other colored tubes you see are usually Argon (Ar) gas filled tubes. More than 150 colors that can be produced using neon and argon.
• compression ratio of an engine – the ratio of the volume of space in a cylinder when the piston is at the top of the stroke to when it is at the bottom of the stroke. A higher compression ratio generally means higher engine efficiency.
• compressive stress – the stress applied to materials resulting in their compaction (decrease of volume). When a material is subjected to compressive stress then this material is under compression. Usually compressive stress applied to bars, columns, etc. leads to shortening.
• compressor
• copper – metallurgy, ductile, oxidation – Copper is easily shaped into complex curves, so it a good material for making the “skin” of a sculpture like the Statue of Liberty. The statue looks very lifelike with fine details in her face. The “drape” of the folds in her robe look like they were made of fabric. Using copper and tools available at the time, the workers were able to make the huge pieces that could be assembled for the final statue. The surface turns green through oxidation after prolonged exposure to the weather in New York harbor. Copper is not very strong, so the statue was designed with an iron framework inside to hold the shape and support the weight of the copper skin of statue.
• Counterweight – a mass attached to the rear of the forklift truck frame. The purpose of the counterweight is to counterbalance the load being lifted. In an electric forklift the large lead-acid battery itself may serve as part of the counterweight.
• Cutaway – If a parachute is tangled or fails to open, the skydiver needs to be able to release or “cutaway” the defective parachute, get clear air and launch the spare emergency chute. This all has to be done in a few seconds as the skydiver is falling to earth. In some cases, the defective chute may have partially filled so there is considerable pressure on the harness, making it even more difficult to remove. 3-Ring release system animation. It allows a skydiver to cutaway a main parachute. Mechanical advantage 200 to 1
• Cylinder – in an internal combustion engine is the space within which a piston travels. Multiple cylinders are commonly arranged side by side in a bank, or ‘block’.
• Digital photography uses an electronic sensor such as a charge-coupled device (CCD) or CMOS semiconductor to record the image as a piece of electronic data rather than as chemical changes on film.
• drag coefficient – a dimensionless quantity that is used to quantify the drag or resistance of an object in a fluid environment such as air or water. It is used in the drag equation, where a lower drag coefficient indicates the object will have less aerodynamic or hydrodynamic drag. The drag coefficient is always associated with a particular surface area.
• drag coefficient – a dimensionless quantity that is used to quantify the drag or resistance of an object in a fluid environment such as air or water. It is used in the drag equation, where a lower drag coefficient indicates the object will have less aerodynamic or hydrodynamic drag. The drag coefficient is always associated with a particular surface area.
• Drainage is the natural or artificial removal of surface and sub-surface water from a given area. Many agricultural soils need drainage to improve production or to manage water supplies.
• dynamics
• dynamics – Bridges actually move a lot even if the distances may be very small. Wind, the number of cars, the loads on the trucks crossing the bridge will cause the bridge structure to move just a fraction of an inch. This is considered Dynamics.
• electric motor – Current flows through the wire coil and creates an electromagnet. One face of the coil becomes a north pole, the other a south pole. The permanent magnet attracts its opposite pole on the coil and repels its like pole, causing the coil to spin.
• electrical circuits – to deliver the correct amount of electric current from the battery through the capacitors to stimulate the heart when needed
• electromagnetic field – a field composed of two related fields ‚Äîthe electric field and the magnetic field.
• Electromagnetic Force –
• electronics – the study and use of electrical parts and circuits. These “electronic components” manipulate the force of electricity. There are many electronic components that are used in electrical devices such as – resistors, capacitors, coils of wire called inductors, integrated circuits, connection wires and circuit boards.
• embedded systems – takes the input from the sensors detecting heart beats, determine when there is a problem and direct the circuity to deliver electric current as necessary
• Engineering is about problem solving. Many of life’s little problems can be solved by an engineer with the right tools.
• ferrous – indicate the presence of iron, mostly in metallurgy or related industries.
• fiber optic cable
• fluid dynamics – One of the key components of a waterslide is water, of course. However, making sure that there is water flowing over the entire surface as riders make their way through the twists and turns on their way to the bottom requires a lot of planning and testing. Too much water is unnecessary and wasteful. Too little water can be unsafe and uncomfortable for the riders. Engineering is required to get it just right
• Fork Positioner – is a hydraulic attachment that moves the tines (forks) together or apart. This removes the need for the operator to manually adjust the tines for different sized loads.
• four-stroke (Otto} cycle – four strokes, or straight movements in a single direction, of a piston inside a cylinder: 1. intake (induction) stroke, 2. compression stroke, 3. power (ignition) stroke, 4. exhaust stroke
• free-body diagram of a projectile would show a single force acting downwards and labeled force of gravity (or simply Fgrav). Regardless of whether a projectile is moving downwards, upwards, upwards and rightwards, or downwards and leftwards, the free-body diagram of the projectile is still as depicted in the diagram at the right. By definition, a projectile is any object upon which the only force is gravity.
• friction – the resistive force that occurs when two surfaces travel along each other when forced together. It causes physical deformation and heat buildup. The frictional force is the force pressing the surfaces together and the coefficient of friction between the materials. The coefficient of friction depends on the materials used — for example, ice on metal has a very low coefficient of friction (they rub together very easily), while rubber on pavement has a very high coefficient of friction (they do not rub together easily). The force of friction is always exerted in a direction that opposes movement.
• geostationary orbit – Satellites in geostationary orbit, such as the current GOES and the future GOES-R, are ‚Äúparked‚Äù above the equator. They orbit Earth just once a day. As Earth spins on its axis, a geostationary satellite always ‚Äúhangs in the sky‚Äù over the same spot on Earth.
• Gimbal – a device to control rotation. The device is usually a set of two or three rings mounted on axes at right angles so as to allow a Ferris wheel seat to remain suspended in a horizontal plane, regardless of the motion of its support.
• graphite – Carbon. Thin flakes are flexible but inelastic, mineral can leave black marks on hands and paper, conducts electricity, and displays superlubricity. Graphite powder is used as a dry lubricant.
• grasping
• gravity, weight and mass – we say things fall because the Earth’s gravity pulls on them. Weight changes when the pull of gravity changes. The Moon is much smaller and the pull of gravity on the Moon is about 1/6th that of Earth. So any object on the Moon weighs 1/6th of its weight on Earth. What does not change is the amount of matter in an object. That is called its mass. On Earth, mass and weight are the same, for practical purposes.
• heat exchange
• heat transfer – transfer of heat is normally from a high temperature object to a lower temperature object. Heat transfer changes the internal energy of both systems involved according to the First Law of Thermodynamics.
• Horizontal stabilizers – deployed to prevent the vehicle from tipping laterally when the arm is extended.
• humidifier – The most common type of humidifier is called an evaporative humidifier. A reservoir holds cold water and dispenses it into a basin. A wicking filter absorbs the water from the basin. A fan then blows air through the moistened filter. As the air passes through the filter, it evaporates some of the water there.
• HVAC (pronounced”H-VAK”) stands for “heating, ventilation and air-conditioning”. This is sometimes referred to as climate control. These three functions are closely interrelated, as they control the temperature and humidity of the air within a building in addition to providing for smoke control, maintaining pressure relationships between spaces, and providing fresh air for occupants. In modern building designs, the design, installation and control systems of these functions are integrated into a single “HVAC” system.
• Hydraulic press – moving the weight of the blade and the material being moved. The addition of power down-force provided by hydraulic cylinders instead of just the weight of the blade made them the preferred excavation machine.
• hydraulic ram
• Hydroacoustics – an electrical impulse from a transmitter is converted into a sound wave by an underwater transducer, called a hydrophone, and sent into the water. When the wave strikes something such as a fish, it is reflected back and displays size, composition, and shape of the object. The exact extent of what can be discerned depends on the frequency and power of the pulse transmitted. Knowing that the speed of the wave in the water is 4921 ft/s (1500 m/s) in seawater, 4800 ft/s (1463 m/s) in freshwater (typical values used by commercial fish finders), the distance to the object that reflected the wave can be determined.
• hydrophilic – Strongly attracted to (or readily dissolving in) water.
• hydrophobic – Repelling (or not absorbing) water.
• image sensor – In a digital camera, the lens forms an image of the scene on a small electronic chip called the image sensor]. The sensor measures this light and converts it to a digital image.
• inert – something that is not chemically active. The noble gases were described as being inert because they did not react with the other elements or themselves.
• Inertia – the tendency of a body to maintain its state of uniform motion unless acted on by an external force. This is called Newton’s first law of motion, taken from Galileo’s principle.
• ionizing radiation – carries a large energy in each particle, can change things that it hits, hurting people or animals or causing chemical changes.
• kinetic energy – the energy that moving objects have. Kinetic energy is the energy of movement.
• Lift – Lift is created as an airstream passes by an airfoil and is deflected downward. The force created by this deflection of the air creates an equal and opposite force upward on an airfoil (see Newton’s third law.) Both the top and bottom surfaces of the airfoil play important roles in deflecting the airflow downward. Nearly any shape will produce lift if tilted with respect to the air flow direction (inclined) or cambered (curved). However, most shapes will be very inefficient and create a great deal of drag. One of the primary goals of airfoil design is to devise a shape that produces the most lift while producing the least drag.
• light emission from gas discharge – electricity flows through the tube. The electricity charges the gas and creates plasma inside of the tube. The plasma glows a special color depending on what kind of gas is inside.
• locking mechanism – over-center action
• locking system – extensive engineering studies favored a canal using a lock system to raise and lower ships from a large reservoir 85 ft (26 m) above sea level. The water to fill and empty the locks would be taken from Gatun Lake by opening and closing enormous gates and valves and letting gravity propel the water from the lake.
• lubricant – A common way to reduce friction is by using a lubricant such as oil that is placed between the two surfaces, often dramatically lessening the coefficient of friction.
• marble – metamorphosed limestone, composed of fairly pure calcite (a crystalline form of calcium carbonate, CaCO3). It is extensively used for sculpture, as a building material, and in many other applications.
• Mast – the vertical assembly that does the work of raising and lowering the load. It is made up of interlocking rails that also provide lateral stability. The interlocking rails may either have rollers or bushings as guides. The mast is driven hydraulically, and operated by one or more hydraulic cylinders directly or using chains from the cylinder/s.
• material fatigue – Some materials will breakdown or fatigue with use and time. Some materials will withstand bending with wind and traffic without much change. Other materials will fail after repeated bending and flexing.
• metallurgy – the composition of the metal case that is small and light as well as bio-non-reactive for housing the electrical components surgically implanted into the patient’s chest
• methane – a hydrocarbon that is a gas at room temperature (20¬∞C). It is often found as the main part of natural gas. It oxidates carbon dioxide and water.
• motherboard : The principal board that has connectors for attaching devices to the bus. Typically, the mother board contains the CPU, memory, and basic controllers for the system. On PCs, the motherboard is often called the system board or mainboard.
• motion – a change in the position of a body with respect to time, as measured by a particular observer in a particular frame of reference.
• no mechanical lock or spring pressure, but is kept in the open position during use by the leverage imparted by the user’s hand.
• non-ferrous metals – metals that have no iron in them at all.
• non-ionizing radiation – does not cause microscopic damage, but some types can cause chemical changes or make things hotter.
• Ohm’s Law – Resistance, discovered by Georg Simon Ohm in 1827, is the ratio between voltage and current. Ohm’s law said that the voltage between any two points in a conductor changes directly as the current between the two points, given the temperature remains the same.
• orthographic
• Other areas include geology of the bridge foundations, the study of the wind forces on the bridge, metal strengths, load carrying abilities and transferring to the foundations
• phase change heat pump – converts a refrigerant from gas to liquid and back again by compression in a refrigeration cycle.
• photovoltaic cells – photovoltaic meaning literally “light-electricity”. Solar cells or PV cells rely on the photovoltaic effect to absorb the energy of the sun and cause current to flow between two oppositely charged layers. A solar cell, or photovoltaic cell, a semiconductor device consisting of a large-area p-n junction diode, which, in the presence of sunlight is capable of generating usable electrical energy.
• Polyethylene terephthalate (PET) – a thermoplastic polymer resin of the polyester family. It is used in synthetic fibers; beverage, food and other liquid containers
• polymer – Substances whose molecules are made of long chains of repeating groups of atoms. Manufactured polymers include nylon, polyvinyl chloride (better known as PVC) and many types of plastics. Natural polymers include rubber, silk and cellulose (found in plants and used to make paper, for example).
• Portcullis – (from the French porte coulissante or gliding door) is a latticed grille made of wood, metal or a combination of the two. Portcullises fortified the entrances to many medieval castles, securely closing off the castle during time of attack or siege. Each portcullis was mounted in vertical grooves in castle walls and could be raised or lowered quickly by means of chains or ropes attached to an internal winch.
• Pressure as Stored Energy
• Printed Circuit Board (PCB) – a thin plate on which chips and other electronic components are placed. Computers consist of one or more boards, often called cards or adapters.
• programmable – the ability to program a computer ‚Äî provide it with a set of instructions for execution ‚Äî without physically reconfiguring the machine is a fundamental design feature of most computers.
• Projectile at an angle (video 12:46) – The men launching the trebuchet were remarkably accurate in hurling rocks at enemy castles and fortresses. They figured out what worked and did it. Later on, someone discovered the math and physics that explained it. They knew the performance characteristics of the machine – length of beam, force of the release. They determined the distance to the castle and the weight (mass) of the rock. From that they were able to determine the angle of the path for the rock to reach the target. They adjusted the trebuchet so the rock traveled that path once it was released.
• refrigeration – the cooling of a body by the transfer of a portion of its heat away from it.
• regular pliers
• resistance – the repulsion of a current within a circuit. It explains the relationship between voltage (amount of electrical pressure) and the current (flow of electricity).
• Rotation – the movement of a body in such a way that the distance between a certain fixed point and any given point of that body remains constant. In 3-dimensional space, for a given rotational movement there is more than one fixed point: these form a line known as the axis of rotation. An object may allow rotation with respect to an attached other object by means of one or more hinges .
• screw – used to make the adjustable wrench adjustable. Rotating the screw, connected to the movable side of the wrench makes the moveable side move in and out.
• semiconductor – a material with an electrical conductance that is intermediate to those of an insulator and a conductor. A semiconductor behaves as an insulator at very low temperature, and has an appreciable electrical conductance at room temperature.
• sensor – a device that measures a physical quantity and converts it into a ‘signal’ which can be read by an observer or by an instrument.
• Shock Loading – Large but short lived forces, known as shock loading, can cause huge problems for engineers as they can break a structure that is otherwise very strong. Shock loading means the incredibly strong cables used to tow ships can break if they are suddenly pulled tight. Shock loading can also be useful; when you hammer in a nail you are applying a very quick huge force to the nail, causing the material you are hammering into to break, and allowing the nail to move forwards.
• shovel
• Spin – The fixed point can be within the body, in which case the body is said to rotate upon itself.
• standards
• statics – We usually think about a bridge just standing in place. The forces and loads associated with a stationary object are addressed in “Statics”.
• strength of materials – The engineer needs to know how strong of each of the materials in the bridge, to ensure that the bridge will support its own weight as well as that of the load – cars, trucks, trains, etc that will be crossing the bridge.
• stress and strain – These are specific kinds of changes that occur during the life of a bridge.
• Strong magnets are used to separate out ferrous metals (tin-plated or steel cans), while non-ferrous metals are ejected by magnetic eddy currents.
• structural analysis – the determination of the effects of loads on physical structures and their components. Structures subject to this type of analysis must withstand loads, such as buildings, bridges, vehicles, machinery, furniture, attire, soil strata, prostheses and biological tissue. Structural analysis incorporates the fields of applied mechanics, materials science and applied mathematics to compute a structure’s deformations, internal forces, stresses, support reactions, accelerations, and stability. The results of the analysis are used to verify a structure’s fitness for use, often saving physical tests. Structural analysis is a key part of the engineering design of structures.
• Surface tension – an important factor in boat and water craft design
• surface tension – many desalination units rely on surface tension. Sea water evaporates in a closed container, the salt is left behind. The fresh water condenses, and can be drained off thanks to surface tension.
• Surface tension is caused by the attraction between the molecules of the liquid, due to various intermolecular forces. In the bulk of the liquid each molecule is pulled equally in all directions by neighbouring liquid molecules, resulting in a net force of zero. At the surface of the liquid, the molecules are pulled inwards by other molecules deeper inside the liquid, but there are no liquid molecules on the outside to balance these forces, so the surface molecules are subject to an inward force of molecular attraction which is balanced by the resistance of the liquid to compression.
• tempering
• tensile strength – The Golden Gate Bridge deck is supported by steel cables. A single steel cable can not support the entire weight, but many cables working together can. Engineers calculate the load and the tensile strength of the cable to determine how many cables are required to support the bridge. They add in a margin of safety – some extra capacity to be on the safe side.
• tension – The button can slip through the slit or buttonhole, and relies on strain or tension pulling out to the sides to keep it in place
• thermal energy of sunlight can also be captured and used for water heating and space heating; various active solar methods are used to collect heat from sunlight and store it for later use.
• thermoplastic – a material which becomes soft when heated and hard when cooled. Thermoplastic materials are used for electronics to protect against electrostatic discharge and radio frequency interference. They can be recycled.
• third class lever
• Third law of thermodynamics – any closed system will tend to minimize its free energy. Without any outside influence, any reaction mixture, too, will try to do the same.
• Tip speed ratio – The ratio between the speed of the wind and the speed of the tips of the blades of a wind turbine. Modern wind turbines are designed to spin at varying speeds (a consequence of their generator design). Use of aluminum and composites in their blades has contributed to low rotational inertia. Newer wind turbines can accelerate quickly if the winds pick up, keeping the tip speed ratio more nearly constant. Operating closer to their optimal tip speed ratio during energetic gusts of wind allows wind turbines to improve energy capture from sudden gusts that are typical in urban settings.
• Titanium – a very strong metal. It does not corrode, and is resistent to sea water and chlorine. It is used in making the strongest and lightest parts of modern fighter jet planes and medical devices.
• Torque – the tendency of a force to turn or twist. If a force is used to begin to spin an object, or to stop an object from spinning, a torque is made. The force applied to a lever, multiplied by the distance from the lever’s fulcrum, multiplied again by the sine of the angle created, is described as torque.
• torsion – a twisting force
• Touch – The sense of touch is spread through the whole body. Nerve endings in the skin and in other parts of the body send information to the brain. There are four kinds of touch sensations that can be identified: cold, heat, contact, and pain.
• toxic – Poisonous or able to harm or kill cells, tissues or whole organisms. The measure of risk posed by such a poison is its toxicity.
• track
• tracks
• turning
• two-part articulated arm
• ultraviolet – part of the electromagnetic spectrum beyond the visible violet light in terms of frequency, wavelength, and energy. Its wavelengths are between about 10 nanometers (nm) about 400 nanometers.
• unlocking
• UVA (between 320 and 400 nanometres), which damages the skin with more long-term effects, such as premature skin aging.
• UVB (ultraviolet radiation with wavelength between 290 and 320 nanometres), which can cause sunburn
• Vacuum in space – Much of outer space is an almost perfect vacuum, with only a small number of atoms per cubic metre, the most common being hydrogen (H) and helium (He), dust, photons (background radiation), and neutrinos. The current temperature is about 3 K – about 3 degrees above the absolute zero of temperature. Neither these photons nor the neutrinos produce a significant interaction with matter, so stars, planets and spacecraft move freely in this near perfect vacuum of interstellar space.
• velocity – a measure of how fast something has moved in a particular direction. In physics, velocity means the time it took an object to move from one place to another (displacement), and the direction of movement
• Viscosity – the viscosity of the hydraulic fluid is an important factor in designing the capacity of the lift system.
• visualization
• voltage
• Wall tension – LaPlace’s Law – The larger the vessel radius, the larger the wall tension required to withstand a given internal fluid pressure. Soda or beer in a can exerts pressure on the can wall. This is an important consideration in determining how thick the aluminum can needs to be.
• water pump – to transport water from source to desalination facility, and for fresh water distribution – pumping capacity necessary to move the volume of water being processed based on distance and change in elevation.
• Water to electric power – Hydroelectric dam A – reservoir, B – powerhouse, C – turbine, D – generator, E – intake, F – penstock, G – long distance power lines, H – river. Water from the river is diverted down to the powerhouse where it turns a generator. Electricity from the generator is tranmited to the grid and users through the long distance power lines.
• watt is the rate a source of energy uses or produces one joule during one second. The more watts, the more energy used per second.
• wavelength – the distance between repeating units of a wave pattern.
• wheel lean
• Wind erosion, also known as eolian erosion is the movement of rock and/or sediment by the wind. Windbreaks can be planted to reduce wind erosion. This includes the planting of trees, shrubs, or other vegetation, usually perpendicular to the principal wind direction.
• worm gear (animation) – used to reduce speed. For each complete turn of the worm shaft the gear shaft advances only one tooth of the gear. As the speed is reduced the power to the drive increases correspondingly. Worm gears are a compact, efficient means of substantially decreasing speed and increasing power.
• yensile stress (or tension) – the stress state leading to expansion (volume and/or length of a material tends to increase). Tensile stress is induced by pulling forces across a bar, specimen etc.