basic engineering book

8/6/2019 Basic Engineering Book

1/73

Piston

What is it?

Pistons are round pieces of metal that engage in reciprocating motion (or go up and down) afterbeing moved by a force. Pistons drive many kinds of internal combustion engines.

Give me an example!

Pistons first appeared in steam engines that powered riverboats and railroad engines. Todaypistons power the engines in most trucks and automobiles.

Internal Combustion Engine

What is it?

An internal combustion engine is one that burns fuel in an enclosed, controlled chamber. Theresulting high pressureexhaust gasses are then directed to turn a crankshaft and converted intomechanical energy.

Give me an example!

Most motor vehicles are powered by internal combustion engines. Many use fossil fuels suchas gasoline or diesel oil, and some even burn methane (or natural gas).


2/73

Crankshaft

What is it?

The crankshaft of an internal combustion engine is attached to the pistons. When the pistonsmoveup and down, the crankshaft turns and convertsthe reciprocating motion of the pistons

into rotary motion.

Give me an example!

The crankshaft connects to the vehicle's gearbox(or transmission), which connects to thedriveshaftand differentialto turn the wheels. The crankshaft also uses a belt drive mechanism toturn the camshaft and operate the valves.

Propeller

What is it?

A propeller is a device equipped with bladesthat rotatesat the end of a shaft. Propeller bladesmove air or water and produce thrust.

Give me an example!

Propellers on an airplane are turned by the crankshaft of the engine and pullthe aircraft forwardthrough the air. Propellers on a boat do the opposite: They pushthe boat through the water frombehind.


3/73

Reciprocating Motion

What is it?

Reciprocating Motion is a repeated to-and-fro, back-and-forth, up-and-down, or side-to-sideform of linear motion.

Give me an example!

Have you ever watched someone playing with a yoyo? The up-and-down motion of the yoyo is anexample of reciprocating motion. Another example is the up-and-down motion of pistons insidea car's engine.

Linear Motion

What is it?

Linear motion is movement in a straight line. Another way to think of linear motion is going frompoint A to point B.

Give me an example!

Many machines work by otherkinds of motion, such as the rotary motionthat makes pistons,sewing machines, and rack & pinion steering mechanisms work. That's why converting rotary


4/73

motion to linear motion is very important. On the other hand, sometimes linear motion must beconverted to rotary motion, like in a steam engine

Rotary Motion

What is it?

Rotary motion is when an object moves in a circle centered around a specific point called anaxis. In other words, when something is turning around and around, it is said to have rotarymotion.

Give me an example!

Stand up and turn around. The motion you just completed is called rotary motion because everypart of your body turned around an imaginary point in space called an axis. The wheels of abicycle also turn in rotary motion, and so does the propeller on an airplane and the crankshaft ina car engine.

Wheel

What is it?

A wheel is a disk shaped object, which transfers linear motion into rotary motion.

The wheelandaxleis a simple machine that makes it easier to move heavy loads! Many peopleconsider the wheel and axle as a kind of lever, with the center of the axle serving as a fulcrum.


5/73

Rollerswere the forerunner of the wheel, with several logs placed under some heavy object.

Give me an example!

Have you ever ridden on a bicycle? Bicycles have a wheel in the front that turns for steering anda wheel in the back that you provide torque to by pushing down on the pedals and moving achain which turns the sprocket in the center of the wheel.

Without wheels, most of the things that move in the world wouldn't be able to go anywhere! Cars,busses, trains even airplanes have wheels (called landing gear) for moving on the ground. Howmany sets of wheels do you use every day?

Steam

What is it?

Steam is water in gasseousstate. Steam is generated by bringing water to its boiling point.

Give me an example!

The first railroad locomotives were powered by steam. Coal fires heated water in the locomotive'shuge boiler to generate steam. The steam was then used to push a gigantic piston, which movedthe locomotive's driving wheels. Steam was even used to blow the train's whistle!


6/73

Boiling Point

What is it?

The boiling point of a substance (a compound or element) is the temperatureat which thatsubstance turns from a liquid to a gas.

Give me an example!

Water reaches its boiling point at a temperature of 100 degrees Celsius (equal to 212 degreesFahrenheit). That is the temperatureat which liquid water turns into steam, a gas. When you hearthe tea kettle whistle, you know you have successfully raised the water inside to its boiling point!

Steam Engine

What is it?

A steam engine is an engine driven by steam power! A steam engine usually has a piston orpistons moving in a reciprocating motion, in a closed cylinder using steam generated by a boiler.

Give me an example!

Before the widespread use of electricity or deisel gasoline, trains were moved along by steamengines!


7/73

Power

What is it?

Power is the rate or speed at which work is done. The more power something has, the faster itcan complete a specific task. We measure the power of machines in units such as the Watt orHorsepower.

Give me an example!

Have you ever overheard people talking about the difference in horsepowerbetween two cars?Horsepower is simply a standard measurement used to rate the amount of work an automobileengine (or any machine) can do in a specific time. An engine that is rated at 200 horsepower has200 times the power to pull a specific load at a specific speed as an average horse. The 200horsepower engine also generates twice the power of a 100 horsepower engine, so it does twiceas much work in a given amount of time ... which makes it faster.

Therefore, the higher the horsepower rating an engine has, the faster a vehicle will move.

State

What is it?

The state of a substance refers to which of the three phases of matterthe substance exists in:


8/73

Solid, liquid, or gas.

Give me an example!

Water exists in all three states (or phases of matter) in our world every day. Water in the solidstate can be found in the freezer as ice cubes. Water in the liquid state comes out of the faucet.And water in the gas state is steam, which comes out of a clothes iron or the tea kettle.

Boiler

What is it?

A boiler is a tank in which water or some other liquid is boiled. The resulting superheated andpressurized vapor (or steam, in the case of water)is convertedto mechanical energy by pushing apiston or turning a turbine.

Because of the intense heat and pressures, boilers must be free of leaks and made of materialswith a high tensile strength - such as steel.

Give me an example!

Have you ever seen an old-fashioned steam locomotive? Steam from the locomotive's boilerpushed a piston that turned the wheels of the locomotive.


9/73

Differential

What is it?

A differential gets its name from its ability to turn power in different directionsor at different

speeds. What makes the differential special is that it allows the two output shafts to spin atdifferent speeds. There are other methods of accomplishing this task, but the most common wayuses a grouping of gears.

Give me an example!

When a car makes a turn, the wheels on one side of the car have to turn fasterthan the wheelson the other side. If there was one full axle between those wheels, the wheels couldn't turn atdifferent speeds. That's why we use a differential and two half-shafts between the two wheels.

the Bernoulli Principle

What is it?

Bernoulli's Principle is a law of physics that has to do with gasses (such as air) and liquids (likewater). It states that when the velocity (speed) of a gas or liquid is increased, its pressurebecomes lower.

Give me an example!

When air rushes over the curved top of an aircraft wing, it goes faster than when it passes overthe flat bottom of the wing. Therefore, the pressure or force of the air pressing down on the top ofthe wing becomes less than the force of the air pressing up on the bottom of the wing. The resultis lift, one of the Four Forces of Flight


10/73

Four Forces of Flight

What is it?

The Four Forces of Flight are lift, thrust, gravity, and drag. Together they explain why objects

that are heavier than air can become airborne and stay that way. These forces are constantlyacting on all flying objects, and all at the same time!

Give me an example!

Have you ever thrown a Frisbee? As it flies through the air, liftholds the Frisbee up, while thethrustyou gave it with your arm moves it forward. Drageventually overcomes the forward motionor thrust of the Frisbee, and gravityovercomes lift, bringing the Frisbee back to earth again.

Jet Engine

What is it?

A jet engine is an engine that generates thrust by discharging (or shooting out) a jet of gas orliquid toward the rear. Jet engines on aircraft have special nozzles that shoot jets ofsuperheated air and exhaust gases out the back to producejetpropulsion.

Give me an example!


11/73

Have you been on an airplane lately? If it was a big airliner, you probably noticed that there werea couple of huge tubes hanging out there under the wings or attached to the tail. Those tubes arethe jet engines that provide the thrust to help the plane become airborne and move through theair.

Thrust

What is it?

Thrust is the force that moves objects forward. Without thrust, we would never go anywhere!Thrust is also the opposite force to drag, which tries to keep objects from moving forward.

Give me an example!

Have you ever thrown a dart or paper airplane? The force imparted on the dart or airplane byyour arm is thrust that moves it forward. In aircraft and rockets, thrust is provided by the

backdraft of a turning propeller or by the pressure created by superheated gasses escaping fromthe combustion chamber of ajet engine. After lift makes an aircraft airborne, thrust is whatmoves it through the air like when you throw a paper airplane. In most aircraft, the direction ofthrust is controlled by flaps called rudders and ailerons


12/73

Tensile Strength

What is it?

Tensile strength is the maximumamount of stretching stress a material can withstand before it

tears. Materials rated at a hightensile strength are durable and difficultto tear.

Give me an example!

Lightweight materials with a high tensile strength are often used in high-performance projectssuch as jet aircraft, race cars, and tennis raquets. Titanium, combined in highly refined steel alloy,is used in eyeglass frames and spacecraft components to provide a high degree of tensilestrength without adding weight.

Fulcrum

What is it?

A fulcrum is the place upon which a lever pivots ... the point that it swivels around... the thing thatit rocks up and down on, or back and forth around. Where the fulcrum is positioned on the leverdetermines what mechanical advantage the lever can provide, or how much work it can help youdo.

Give me an example!

Have you ever played on a teeter totter (also called a seesaw)? The board you sat on was anexample of a First Class Lever, and the brace in the middle of the teeter totter was a classicexample of a fulcrum. Did you notice that the farther you sat from the middle (or fulcrum), themore force you could generate by bouncing up and down? In other words, the longer your leverwas, the more mechanical advantage you gained


13/73

Belt Drive

What is it?

A belt drive is a mechanism that uses belts and pulleys to transfer rotary motion (input energy)into output energy. When you turn one pulley in a belt drive system, another pulley will turn.

Give me an example!

Some belt drive systems contain lots of pulleys. In the belt drive model pictured here, notice thatthere are a bunch of pulleys and belts transferring rotary motion to many different parts of thesame machine! See if you can tell which way each of the axles would turn if just one of them isrotated. Do they all turn in the same direction?

Camshaft

What is it?

The camshaft of an internal combustion engine is a shaft equipped with cams that turns in timewith the crankshaft. The cams press down on the inlet valves and exhaust valves to make themopen and close.

Give me an example!

Most engines have their camshafts on top of the engine block so that the valves can be easily


14/73

opened and closed. This type of engine is called an overhead cam (or OHC) engine and was firstintroduced in racecars.

Natural Gas

What is it?

Natural gas is another name for methane(CH4). Methane gases are also hydrocarbons. Naturalgas is one of the fossil fuels, and therefore nota renewable resource.

Give me an example!

Natural gas is used to fire furnaces and hot water heaters in many homes. Natural gas burnsvery cleanlyand does not produce harmful by-products. Does your home have a gas or electricfurnace? How about the hot water heater?


15/73

Fuel

What is it?

Fuel is a substance that is consumed(or burned) in order to do work.

Give me an example!

Internal combustion engines use gasoline and diesel oil as fuel. Campfires burn wood as fuel.Furnaces and water heaters burn natural gas as fuel.

Airplane

What is it?

An airplane is a vehicle that is capable of leaving the ground and flying through the air.

Give me an example!

Airplanes have wings which work because of the Bernoulli Principle. Airplanes can take off andfly because of the four forces of flight -- lift, drag, gravity, and thrust. If the airplane has an engine(either ajet engine or one with a propeller), the engine provides the thrust. If an airplane doesn'thave an engine, it's called a glider

Fossil Fuels


16/73

What is it?

Fossil fuels are made from the compressed remains of ancient plants and animals (calledfossils). Most internal combustion engines that power everything from jet planes to automobilesand railroad locomotives run on fossil fuels.

Give me an example!

Fossil fuels include peat, coal, gasoline, heating oil, methane (natural gas), diesel fuel, andkerosene. Fossil fuels are nota renewable resource, which means that once they areconsumed, they are gone forever.

Watt

What is it?

A watt is a unit of power in the meter-kilogram-second system. It is equal to the power developedin a circuit by a current of one ampere flowing through a potential difference of one volt.

Give me an example!

The watt is named for James Watt, a famous engineer. One watt equals one joule per second, orapproximately .0013441 horsepower! It is symbolized W.


17/73

Horsepower

What is it?

Horsepower is a unit of power for measuring motors and engines. It is equal to 550 foot-poundsper second, (the force needed to raise 550 pounds one foot in one second) or approximatley

745.7 watts. Abbreviated hp.

Give me an example!

An one horsepower engine could raise a 550 pound weight about a foot every second

Stress

What is it?

Stress is a force that is exerted on a solid material from the outside.

Give me an example!

The stronger and more solid something is, the more stress it can tolerate. That is why we buildbridges out of steel girders instead of jelly!


18/73

Force

What is it?

Force is anything that acts on a body to changeits rate of acceleration or alter its momentum.

Give me an example!

If you attach a motor to a toy glider, the force generated by the motor will make the glider gofaster(or change its acceleration and momentum).

In the game of chess, a force is a move necessitated by circumstances, such as a check

Turbine

What is it?

Turbines are wheels or cylinders with fins on their outsides. When a stream of gas or liquidpasses over a turbine, the turbine spins around a shaft and creates mechanical energy.

Turbines are found insidejet engines, where they are turned rapidly by superheated streams ofexhaust gasses. Turbines are also used to generate electricity by harnessing the constant flow ofwater in a river to turn them.

Give me an example!

Have you ever watched a pinwheel turn in the wind? That's exactlywhat takes place inside a jetengine - except the turbine is much bigger and it is turned by hot exhaust gasses instead of agentle breeze!


19/73

Chain

What is it?

A chain is a series of links or loops that are all hooked together. Chains are usually made out ofmetal, but can be made out of just about anything.

Give me an example!

Check out the chain on your bicycle. The gears(or sprockets) on your bicycle have teeth thatstick into the holes in the links of the chain. When you push down on the pedal with your foot andapply torque, the sprockets turn and the chain moves, which creates a transfer of power to thewheels

Fins

What is it?

Fins are airfoils or flat plates that stick out from the main body of an object

Fins on a turbine stick out and catch the passing flow of air or water to turn the turbine. Someaircraft have adjustablefins called rudders and aileronsthat allow the pilot to steer by directingairflow.

Give me an example!

Have you ever seen a windmill? As wind blows, it catches in the fins of the windmill and turns


20/73

them and the shaft to which they are connected. This produces mechanical energy that is used topump water out of the ground

Torque

What is it?

Torque is the ability of a force to produce rotary motion.

Give me an example!

Have you ever climbed a steep hill on a bicycle? Remember how muchforce you had to use toturn the pedals? That force was torque. It turned the crank that turned the sprockets that turnedthe wheels of the bicycle to produce rotary motion. It takes more torque to pedal uphillthandownhill.

Torque can be measured by taking the product of the force and the perpendicular distance from

the line of action of the force to the axis of rotation.

Gear

What is it?

A gear is a wheel with teeth around the outside of it. The teethare designed to fit between the


21/73

teeth on other gears. The teeth engage with other gears or chains to transfer power from onepart of a machine or system to another.

Give me an example!

Have you ever taken a close look at the chain and sprockets on a bicycle? The sprockets arewheels with teeth around their edges, and therefore they are gears. They transfer power fromyour legs to the chain and then on to the sprocket attached to the back wheel, which makes theback wheel turn.

Gears are found in many machines including cars, farm equipment and even kitchen appliances!

Transfer of Power

What is it?

Transfer of power is when power moves through a system from the point of input to the point ofoutput.

Give me an example!

In a car engine, fuel is burned, causing pistons to rise and fall. The reciprocating motion of thepistons is changed to rotary motion, which is then turn transfered from gears to axles to thewheels of the car where it is output as motion. This transfer of power is what turns fuel intomotion


22/73

Propulsion

What is it?

Propulsion is when a body is movedin some direction because forceis applied to it.

Give me an example!

Propulsion can come from many different sources. Wind energy pressing against a sail movesboats through water. Thrust from ajet engine provides propulsion to aircraft. Mechanical energygenerated by an internal combustion engine moves an automobile.

Nozzle

What is it?

A Nozzle is a tubethrough which a gas or liquid flows under pressure.

Jet engines pass their hot exhaust gasses out through a nozzle to provide propulsionto theaircraft.

Give me an example!

Have you ever wondered how spray paint works? The paint is under pressure inside the can.When you push down on the button on the top with your finger, a valve opens and the paintcomes out through a nozzle. Without a nozzle to direct the flow of the paint, it would just explodeall over everything!


23/73

Ampere

What is it?

Amperes (or Amps) are units that measure the flow of current through a system. One Ampere isequal to 6.3 billion electrons per second.

Give me an example!

Fuses are rated by the number of Amperes of current they will tolerate before the piece of metalinside them melts and breaks the circuit, which acts like a switch to turn the system off. A 30-Ampfuse will tolerate 30 Amperes of current before it blows, or shuts down.

Half-shaft

What is it?

A differential housing needs two shafts, or axles, in order to do exactly what it is famous for:turning power in different directionsor at different speeds. Half-shafts are the two axles that turnthe gears inside the differential housing unit.

Give me an example!

When a car makes a turn, the wheels on one side of the car have to turn fasterthan the wheelson the other side. If there was just one single full axle between those wheels, the wheels couldnotturn at differentspeeds. Using two half-shafts and a differential between the two wheelsallows them to turn independently


24/73

Input

What is it?

The input of a mechanical system is the place where the power is entered into the system. It is

the very beginning of a process or chain of events that perfoms work.

In LOGO programming, input refers to any value the programmer puts into a procedure to get aresult or an output.

Give me an example!

A great everyday example of input involves steering a car. In this system, the driver inputs thepower by simply turning the steering wheel. Turning the steering wheel sets into motion a chain ofevents known as a transfer of power which conveys power through a series of mechanicaldevices inside the car's steering system. The result is a change in the angle of the car's frontwheels (combined with the forward rotary motion of the wheels), which makes the car turn acorner.

When you add a value to a variable within a procedure, you are said to be inputting that value.With this input, such as placing a number into a variable, LOGO produces an output, such asshape or a design.


25/73

Bicycle

What is it?

A bicycle is a two-wheeled vehicle that is moved by using your feet to turn the pedals.

Give me an example!

Bicycles use a lot of mechanical engineering principles in their construction and movement.Bicycles use gears, levers and the brakes are even a non-linearflexiblesystem! Wow!

Acceleration

What is it?

Acceleration is the rate of changeof velocityover time.

Automotive engineers pay attention to a car's acceleration - or its ability to speed upin a short

amount of time. They rank cars by how fastthey can accelerate (or change velocity) from zero to60 miles per hour.

Give me an example!

Have you ever rolled a ball down an incline? As it starts rolling down the incline, the ball must firstovercome the force called inertia. As it rolls, the ball's velocity increases as gravity takes over.The rate of change in speed is the ball's acceleration


26/73

Axle

What is it?

The axle is a long skinny rod that attaches to the center of a wheel, gear, or pulley. When theaxle turns, whatever is attached to it alsoturns. This makes it possible to transferrotary motion

from one axle to another with gears or pulleys.

Give me an example!

In the picture above, you'll see a good example of how axles can work together with gears andpulleys to get your project rolling!

Airfoil

What is it?

Airfoils are specially designed fins that provides lift when a current of air passes over it. Aircraftwingsare airfoils.

Hydrofoilsperform the same way as airfoils - except in water.

Give me an example!

Have you ever seen one of those little wings they put on the backs of formula one race cars?


27/73

Those are airfoils. Drivers use them to push againstthe wind and provide downwardpressure tokeep the cars from becoming airborne at high speeds.

Rudders and Ailerons

What is it?

Rudders and ailerons are moving panels that steer aircraft by directing thrust.

Give me an example!

Aircraft rudders are attached to the upright portion of the tail and control the left and rightdirection of the aircraft in the same way that a rudder on the back of a boat controls the boat'scourse as it moves through water.

Ailerons are flaps attached to the back edges of the wings and crossmembers of the tail. Whenailerons point down, the flow of air over the top of the wing becomes faster than the airflow underthe wing, creating lift. When ailerons point up, the opposite is true: The airflow over the top of thewing becomes slower than the airflow under the wing, which makes the aircraft lose altitude


28/73

Shaft

What is it?

The shaft of a motor is the moving part that sticks out from the center of the motor. The shaft

enables the motor to transfer rotary motion to produce motion in other parts of the system.

Give me an example!

In an automobile, the shaft sticking out of the back of the motor is called the driveshaft. It turns aseries of gears attached to the car's axle and makes the wheels turn, creating motion. Follow thearrow in the floating motor pictured above to see exactly where the shaft l ives on your modelmotor

Lift

What is it?

Lift is the force that makes an airplane wing or helicopter rotor rise and helps the aircraft escapethe pull of the earth (gravity). Lift is a product of differences in air pressure and is based on theBernoulli Principle.


29/73

Give me an example!

Have you ever noticed how a hawk soars effortlessly in circles in the sky on a summer afternoon?The hawk is giving his wings a rest by taking a free ride on rising, heated columns of air calledthermals that provide lift

Link

What is it?

A link is an individual unit that is part of a chain.

Give me an example!

Different kinds of chains have different kinds of links. Most chains that are used to pull heavyloads or lock things up have links that are simple metal rings. The chain on your bicycle is madeso that it can be turned by the sprockets without slipping off. The links in your bicycle chain aremuch more complicated than the links in a regular chain


30/73

Inlet Valve

What is it?

The inlet valve in an internal combustion engineopensto allow fuel to flow into the cylinder for

combustion. Then the inlet valveclosesduring combustion until it is needed again to repeat thecycle. Inlet valves are operated by the camshaft and are found on engines equipped with eithercarburetors or fuel injection systems.

Give me an example!

Over time, the combustion chamber at the top of the cylinder sometimes becomes coated withresidue, which can cause the inlet valves to stick (or not open and close properly). There aremany cleaning solutionsyou can add to your gas tank (called gasoline additives) that will helpcleanthe inlet valves.

Exhaust Valve

What is it?

The exhaust valves in an internal combustion engineopenafter the fuel has been burned toallow the exhaust gassesto exitthe combustion chamber. Like the inlet valves, exhaust valvesare opened and closed by the camshaft.


31/73

Give me an example!

The exhaust valve is located near the inlet valveat the top of the cylinder. Exhaust gasses passthrough the exhaust valve, travel down pipes to the exhaust manifold, and then on through themuffler and out the tailpipe

Engage

What is it?

When one gear turns another, we say they engage or meshwith each other. Every gear hasteethon its outer edge which act like tiny levers. As we know, levers are used to lift things. Whenone gear's teeth (or tiny levers) lift the teeth of another gear, the second gear turns about its axis(or central anchor point). The result is what we call transfer of power between the gears.

Give me an example!

The front and rear sprockets on your bicycle are gears (note the teethon their outer edges).When you push down on the pedals, these teeth engage or mesh with the spaces between thelinks in the bicycle chain to move the chain and turn the rear wheel.


32/73

Velocity

What is it?

Velocity means speed- or the distance an object travelsdivided by the timeit took to make the

trip. Velocity may change over the course of a journey, and therefore may be calculated for aparticular portionof a journey or for any specific pointin the journey.

Give me an example!

Have you ever watched the speedometer of a car while driving in traffic? The needle is constantlyin motion to indicate that the car is speeding up and slowing down, or changing its velocity.What's more, you can use the speedometer reading to determine the car's velocity at any givenpoint in the trip

InertiaWhat is it?

In physics, inertia is the force of nature that makes matter tend to maintain or stay in its currentstate of motion. Inertia is the resistance of objects to any change in their speed. Every object hasinertia, and the amount of inertia an object has is directly related to the amount of mass it has;the more mass, the more inertia, and therefore the more resistance to change in speed.


33/73


34/73

Pulley

What is it?

A pulley is a wheel with a groove around the edge. Pulleys can be used as a simple machine to

change the direction of a pulling force. By throwing a rope or chain over a pulley, you can liftsomething upby pulling down.

Give me an example!

If you hook several pulleys up in series, you can create a mechanical advantage and lift severaltimes the weight with less effort. This is called a block and tackle, and is often used to lift pianosand other heavy objects

Rudder

What is it?

A rudder is an oar-shaped device mounted beneath the ships waterline, enabling it to turn. Theyare similar to the rudders and ailerons found on airplanes.

Give me an example!

A rudder controls a boat's course as it moves through water. Ancient Viking longships weresteered by a side rudder. The oldest depiction of a rudder can be found on a pottery model of aChinese ship dating from the first century C.E.


35/73

Momentum

What is it?

The momentum of a body is its massmultiplied by its velocity. A body in motion has more

momentum than the same body at rest.

Give me an example!

If two bodies have the samemass but are traveling at differentvelocities, then the one that istraveling fasterhas moremomentum. If two bodies are traveling at the samevelocity, the onewith the greatermass has moremomentum.

Mass

What is it?

Mass is the physical property that gives objects their resistance to changes in motion. Also, in thepresence of other massiveobjects, it generates the attraction due togravitywhich gives objectstheir weight!

Mass is the amount of matter in an object. The amount does not change because of location, anda bowling ball would have the same mass on the moon and on the Earth.


36/73

Give me an example!

When you hit a volleyball, it might hurt just a bit as it bounces off your hands to go sailing over thenet. That's because, although a volleyball isn't very massive, the mass it does possess makes itresist your effort to change its motion. Bowling balls, on the other hand, possess much moremassthan volleyballs do. If you tried to knock a bowling ball over the net, you just might breakyour arm!

Motion

What is it?

Motion is when a body continues to change position. Another term for motion is movement.

Give me an example!

Some part of your body is in motion 24 hours a day - even when you are asleep! When yousleep, your arms and legs might not move, but your lungsand heartcontinue to pump oxygenand blood through your body.

Weight


37/73

What is it?

Weight is a measurement of the amount of force exerted on a body by gravity. Weight and massare different.

Give me an example!

Your bathroom scale measures your weight - or the amount of force gravity exerts on your body.When you go to the gym and lifta weight, you are using your muscles to overcome the pull ofgravity on a chunk of iron.

Ductility

What is it?

Ductility is the ability of a material to be stretchedinto a new shape withoutbreaking. Ductility isone of the characteristic properties of Metals.

Give me an example!

Have you ever noticed how many differentthings are made out of Aluminum? Everything fromsoft drink cans to airplane parts and engine blocks for automobiles! That is because Aluminum, ametal, has great ductility and can be formed into manyshapes withoutbreaking!


38/73

Pascals Law

What is it?

Pascal's Law states that if you apply pressure to fluids that are confined(or can't flow to

anywhere), the fluids will then transmit(or send out) that same pressure in all directions at thesame rate.

Give me an example!

Have you ever stepped on a balloon? Remember how the balloon bulged out on all sides underyour foot - not just on oneside? That is Pascal's Law in action! The air (our fluid here) wasconfinedby the balloon, and you applied pressurewith your foot.

Magnitude

What is it?

The magnitude of something is its size.

Give me an example!


39/73

Have you ever bounced a ball soft and then bounced it hard? What you were doing wasincreasing the magnitude of the force you applied to the ball.

Automobile

What is it?

Automobiles (or cars) are usually four-wheeled vehicles designed for passenger transportation.

Give me an example!

The first automobile was built by Nicolas-Joseph Cugnot in 1769. Cugnot's vehicle was steampowered and achieved about 2 mph (3.2 kph). Karl Benz and Gottlieb Daimler started theautomobile industry in 1885 in Germany. Henry Ford introduced mass production techniquesthat made automobile production commercially feasible in 1913.

Accuracy


40/73

What is it?

Accuracy is the ability to achieve desired results. Precision is the ability to achieve those sameresults repeatedly.

Give me an example!

If you were shooting at targets and hit a bullseye, you would say that your shooting wasaccurate. If you hit that bullseye 17 times in a row, you would say your shooting was not onlyaccurate, but also very precise

Precision

What is it?

Precision is the ability to achieve the same results repeatedly.

Give me an example!

If you were shooting at targets and hit a bullseye, you would say that your shooting was accurate.If you hit that bullseye 17 times in a row, you would say your shooting was not only accurate, butalso very precise.


41/73

Activation Energy

What is it?

Activation energy is that energy which must be added to a chemical mixture in order to producea chemical reaction at a certain temperature.

Not all chemical reactions occur naturally at a given temperature. In many cases more heatmustbe added in order for the molecules to react. This heat is called activation energy.

Give me an example!

A good example of activation energy is the boilingof water. When water reaches its boilingpoint, it turns from water molecules into water vapor, a mixture of water molecules and gasses.But in order to get water to boil, you must add heat, right? That's why you put the tea kettle on thestove and wait until the water vapor comes whistling out! The stove provides the activationenergy that turns the water into steam.

Aerodynamics

What is it?

Aerodynamics is the study of how air friction effects the performance of vehicles. Scientists use


42/73

wind tunnelswith artificially controlled airflow to study aerodynamics.

Give me an example!

Have you ever noticed the difference between the shape and profile of a sports car and a cargovan? The sports car is designed to go fasterby eliminating more air friction through the use ofaerodynamics

Air-Fuel Ratio

What is it?

The air/fuel ratio is very important to the efficiency of an engine. If the mixture of air and fuel istoo rich(or contains too much fuel) or too lean(too much air), the engine will not burn its fuelefficiently - and it may even stop running all together.

Give me an example!

Have you ever heard someone say their car needs a tune-up? Part of what a mechanic doesduring a tune-up is adjustthe air/fuel ratio so that the engine will run smoother, quieter, andcleaner.


43/73

Angular Acceleration

What is it?

Angular acceleration is a changein angular velocity.

Give me an example!

When a driver pushes down on the accelerator pedal in an automobile, more fuel is sent to theengine, which ultimately changesthe angular velocity of the wheels. This angular accelerationin turn makes the car go faster.

Angular Momentum

What is it?

Angular momentum is the force that keeps a spinning body spinning.

Give me an example!

Have you ever spun a gyroscope? Remember how once it is spinning, it tends to continuespinning? The force of gravity combines with rotational speed to produce angular momentumthat keeps the gyroscope spinning.


44/73

Angular Speed

What is it?

Angular speed is the speed of a rotating body.

Give me an example!

Angular speed is measured in the number of complete turns a spinning wheel or top makes inone minute. This is expressed as revolutions (spins) per minute, or RPM.

Have you ever seen a tachometer in a car? Tachometers measure the number of RPMs thecrankshaft of the engine is doing -- in other words, the speed of the motor, not the speed of thewheels. This helps drivers know when to shift gears to make the most efficient use of the motor'soutput as RPMs change.

Angular Velocity

What is it?


45/73

Angular velocity is the velocity of an object which is in rotary motion. Angular velocity ismeasured in radians per second.

Give me an example!

Imagine a washer tied to a string that is swinging around in a circle (rotary motion). If you swingthe washer at a constantvelocity, you should be able to calculate how far it movesaround thecircle in one secondof time. Then you could take the number of degrees of that angle andmultiply it by piradians per 180 degrees to find the angular velocity

Ball Bearings

What is it?

Ball bearingsreducefriction between fixed and moving parts. Ball bearings are made of smallmetal balls that roll between inner and outer rings.

Give me an example!

Have you ever wondered why the wheels on roller skates turn so easy? They have ball bearingswhere they connect to their axles to eliminate much of the friction between the wheels(movingparts) and the axles (fixedparts).


46/73

Load

What is it?

The term load has several meanings.

In physics, a load is something that must be moved or supported.

In electricity, a load is a device that needs electric current in order to function.

In computer science, loading refers to the placing of information on a computer.

Give me an example!

In a simple machine like a seesaw, the load is the person that just sits there and must be movedor balanced by the person applying the effort.

In an architectural structure, a load is a heavy part of a building that must be supported by astructural member of the building. A roof is part of the load that must be supported by the walls.In an electric circuit, a load is a device that must be powered, such as a lightbulb!

Beam


47/73

What is it?

A beam is a generic term for a structural member that carries a load across between two uprightsupports.

Give me an example!

Joists are wooden beams that hold up the floors in houses. Girders are steel beams that hold upskyscrapers. Rafters are beams that hold up a roof from the inside. Lintels are beams that aresupported by posts.

The architrave, the frieze, and the cornice are examples of beams in classical architecture.

Band Brakes

What is it?

Band brakes work on the principle of friction between a band or belt tightening around a wheel inorder to stop the wheel from turning.

Give me an example!

Many emergency brakes in automobiles are band brakes. Band brakes are also used to stopand slow down assembly lineconveyor belts in factories.


48/73

Vehicle

What is it?

A vehicle is a machine, usually with wheels and an engine which is used for transporting people

or goods on land, mostly on roads.

Give me an example!

A car, truck, motorcycle, and bus are all examples of vehicles!

Automobile

What is it?

Automobiles (or cars) are usually four-wheeled vehicles designed for passenger transportation.

Give me an example!

The first automobile was built by Nicolas-Joseph Cugnot in 1769. Cugnot's vehicle was steampowered and achieved about 2 mph (3.2 kph). Karl Benz and Gottlieb Daimler started theautomobile industry in 1885 in Germany. Henry Ford introduced mass production techniquesthat made automobile production commercially feasible in 1913.


49/73

Assembly Line

What is it?

An assembly line is a mechanical system in a factory where an article is conveyed through

different places, usually by conveyor belt, and different tasks are done to the article.

Give me an example!

The first automobiles that were inexpensive to produce were made on an assembly line byHenry Ford! The vehicle would start at one end of the factory and each worker would add a pieceonto the car, making car production much faster!

Machine

What is it?

In general, a machine is any assemblage of parts that can transmit force, motion, and energy.

Give me an example!

There are many awesome machines! A lemon squeezer, a motor and a sewing machine are allexamples of machines!


50/73

British Thermal Unit

What is it?

A British Thermal Unit (BTU) is the amount of heatneeded to raise the temperature of one

poundof water by one degree Fahrenheit.

Give me an example!

British Thermal Units from the old-fashioned English system, and therefore not often used inmodern scientific experimentation. However, BTUs are frequently used today to measure theoutput of household furnaces. Newer furnaces function with greater efficiency and produce agreater number of BTUs with a given amount of electricity or natural gas.

Brittleness

What is it?

Brittleness is the property of a material that makes it breakeasily withoutbending. Brittleness isthe oppositeof ductility.


51/73

Give me an example!

Have you ever dropped something made of glass and seen it shatter? Glass does this because ofits brittleness.

Buckling

What is it?

Buckling is when an object bendsunder compression from a load. In architecture, bucklingsometimes happens to supporting structural members, such as walls, columns, beams, or posts.

Give me an example!

Have you ever stood on top of an aluminum can until it collapsed? Your weight caused the can tobuckle. To put it another way, you overloaded the can with compression force and caused it to

buckle.

Buckling

What is it?


52/73

Buckling is when an object bendsunder compression from a load. In architecture, bucklingsometimes happens to supporting structural members, such as walls, columns, beams, or posts.

Give me an example!

Have you ever stood on top of an aluminum can until it collapsed? Your weight caused the can tobuckle. To put it another way, you overloaded the can with compression force and caused it tobuckle.

CAD

What is it?

CAD stands for computer-aided design or drafting. It refers to the use of a computer to designsomething (such as art), or in the creation of a technical drawing! CAD is another term for design

software.

Give me an example!

There are many different CAD programs. One great one is POV-RAY, which allows you to create3D images!


53/73

Design Software

What is it?

Design software is simply a computer program that helps you design something.

Give me an example!

BlockCad, GryphonBricks, Lview and LEGOCad are examples of design software that allow youto design LEGO creations

Cantilever

What is it?

In general, a cantilever is any lintel supported by a post, such as a flagpole sticking out from abuilding.

Give me an example!

A cantileveredbeam is one that is supported on one end but appears to "float" at the other. Aflight of steps, a balcony, a cornice, or a canopy may also be built in this way and calledcantilevered


54/73

Cantilever Arm

What is it?

Cantilever arms are architectural elements that project outwards from their supporting post.

They are only supported on one side, and look much very strong diving boards.

Give me an example!

Cantilever arms are often found in cantilever bridges supporting a suspended span.

Cantilever Bridge

What is it?

A cantilever bridge is a bridge constructed of sets of cantilevers that meet in the middle.Cantilever arms project outward from supporting piers and meet in the middle of each span.Sometimes there is a suspended span between the two extended cantilever arms. A cantileverbridge is a form of truss bridge.

Give me an example!

The Forth Railway Bridge (completed in 1890) crossing the Firth of Forth near Queensbury,Scotland, is an example of cantilever bridge.


55/73

Cantilevered

What is it?

A cantilevered structure is one that is supported on one end but not the other.

Give me an example!

A cantileveredbeam is one that is supported on one end but appears to "float" at the other. Aflight of steps, a balcony, a cornice, or a canopy may also be built in this way and calledcantilevered.

Carburetor

What is it?

The carburetor in an internal combustion engine is where the air and fuel are mixedbefore theyare sent to the cylinders for combustion.

Fuel from the fuel pump enters the carburetor and is mixed with clean air coming from the airfilter. When the driver opens the throttle valve, a butterfly valve opens and allows the mixture toflow to the cylinders.

Give me an example!


56/73

Carburetors are not high in efficiency, which is why most automobiles today have fuel injectioninstead. Because of their complex mechanism, carburetors require periodic adjustmentas partof an engine tune-up.

Charles Law

What is it?

Charles' law is one of the gas laws of physics. It states that the volume of a gas is directlyproportional to the temperature of the gas as long as the surrounding pressure remains the same.In other words, if the volume of a gas is increased, the temperature also increases. Likewise, ifthe volume is decreased (and the pressure remains constant), the temperature also is decreased.

Give me an example!

Imagine the air (a common gas) in your bike tire. After a cold night, your bike tire will have cooleddown and will be a little squishy. The tire probably hasn't lost any air, but with the cooler nighttemperatures, the volume has decreased. Later in the day, under a warm sun, the tire feels fullbecause both the temperature and volume have increased, even though you haven't increasedthe air pressure inside the tire!


57/73

Chassis

What is it?

A chassis is the frame of a vehicle, usually including the wheels and engine, onto which a metal

covering is fixed.

Give me an example!

All cars and trucks have a chassis. It is the part that holds all the pieces in place. Consider thechassis like a the frame of a house being built, the walls couldn't stand up unless the frame wasthere. A car would just be a pile of machinery if the chassis wasn't there!!

Combustion

What is it?

Combustion means burning. A combustion reaction gives off light and heat.

Give me an example!

Without combustion, there wouldn't be automobiles! The standard gasoline-powered automobileengine is called an internalcombustion engine. Have you ever noticed how an automobileengine gets hotafter it runs for a while? That's heatproduced by combustion of the liquid fuel


58/73

(gasoline).

You can't seethe lightproduced by the combustion because it's internal(or inside).

Compressor

What is it?

A compressorincreasesthe pressure of a substance that passes through it. Compressors areused in refrigeration and air conditioning equipment.

Give me an example!

Have you ever why the refrigerator makes noise when it is running? The electric pump motorinside the compressor is what makes the noise! The compressorpumpsrefrigerant from theevaporator inside the refrigerator to the condenser outside, adding pressure to the system.

Cone Clutch


59/73

What is it?

A cone clutch serves the same purpose as a disk or plate clutch. However, instead of matingtwo spinning disks, the cone clutch uses two conical(or cone-shaped) surfaces to transmitfriction and torque.

Give me an example!

The cone clutch transfers torque with greater efficiency than the plate clutch because it offers agreater amount of surface area. Remember, friction is caused by the differencesin two surfaces.

Conservation of Mass

What is it?

Conservation of mass is a physical law which states that mass can be convertedfrom one formto another, but mass is neverlost all together.

Give me an example!

When a piece of wood burns, its mass is converted into ashes and gas. Conservation of masssays that the mass of the wood beforeburning is equal to the mass of the ashes and gasses (ifyou could collect them) afterburning. The wood changes form, but its mass is conserved.


60/73

Conservation of Energy

What is it?

Conservation of energy is a physical law which states that energy can be converted to a

different form, but it is neverlost all together.

Give me an example!

When the internal combustion engine in an automobile burns gasoline, it produces heat energy.The engine then uses this heat to drive pistons and turn a crankshaft, convertingthe heat tomechanical energy. The heat energy is not lost - merely changedto another kind of energy.

Crown Gear

What is it?

A crown gear is a gear that looks like a crown with the teeth jutting out at a 90-degree angle tothe wheel. Crown gears are used to change the direction of the powerwhen they engage a spurgear at a 90-degree angle.

Give me an example!


61/73

Did you ever wonder how to change the direction of rotation of the axles in your machine? Oneway to do this is by using a crown gear like in the diagram.

Conservation of Momentum

What is it?

Conservation of momentum means that the momentum of a body will remain constant, as longas no outside forcesact on it.

Give me an example!

Have you ever shot pool? Did you notice how the cue ball moves in a straight lineand at thesame speed-- that is, until it hits a bumper or another ball? The momentumof the cue ball wasconserved up until it was acted upon by an outside force(another ball or a bumper).

Couplings


62/73

What is it?

Couplings are used to connect the ends of shafts.

Give me an example!

Four-wheel-drive vehicles have a special coupling that can be connected and disconnected topower the front axle when you want to use 4WD. When the coupling is engaged to the engine'sdriveshaft, you can go four-wheeling!

Daltons Law

What is it?

Dalton's Law of partial pressures states that the sum of the pressure of each gas equals the totalpressure of a mixture of these gasses.

Give me an example!

John Dalton was an English chemist and is considered a founding father of physical sciencebecause of his many scientific observations and discoveries!


63/73

Damping

What is it?

Damping is when a sound, a vibration, oscillation, motion, or any form of energy is reducedby an

outside force.

Give me an example!

Have you ever rung a small bell and then put your hand on it to stop its ringing? You weredamping (or reducing) the vibration of the bell with your hand.

Deformation

What is it?

Deformation is when the shape or size of something is changeddue to outsidestress. Someforces that cause deformation include heat, cold, gravity, and chemical reactions. Objects oftenexpand or contract due to changes in atmospheric moisture, too.

Give me an example!

Have you ever noticed how wooden doors can be harder to open and close on a rainy day? That


64/73


65/73

What is it?

The direction of motion is the direction an object is moving!

Give me an example!

The direction of motion can be important when steering an automobile or a robot!

Direction of Rotation

What is it?

Direction of rotation is the direction that a wheel, pulley, or gear is turning -- left to right or rightto left.

Give me an example!

Have you ever watched the hands on a clock face? They have a specific direction of rotation asthe hours, minutes, and seconds tick by. This direction of rotation even has its own specialname -- clockwise! If the hands on the clock would somehow start rotating in the oppositedirection, that direction of rotation would be called counterclockwise.


66/73

Directional Movement

What is it?

Directional movement is movement in a single direction.

Give me an example!

Have you ever ridden an old-fashioned bicycle with a coaster brake? The pedals on those bikeswill only go so that you can move forward -- if you try and pedal backward, you hit the brake!That's an example of directional movement

Disk Brakes

What is it?

Disk brakes operate by means of a spinning disk attached to the car's wheel. When the driverpresses on the brake pedal, the car's hydraulic system causes two calipers to pushthe brakepads onto the disk. This generates frictionand slows the turning of the wheel.

Give me an example!

Have you heard of a car's brakes overheating? This means that too much frictionhas beenproduced by the brake pads rubbing on the disk. This sometimes happens when driving downlong, steep mountain roads where brakes are used frequently. All the driver needs to do then ispull over and let the brakes cool down


67/73

Disk Drive

What is it?

A disk drive is a device that reads and writes data to and from a disk. The two most commontypes of disk drive are a floppy disk drive and a hard drive.

Give me an example!

To save information to a diskette, you would put the disk into the disk drive. It would then storeof retrieve your information and load it onto your computer.

Disk Or Plate Clutch

What is it?

A disk or plate clutch is a device that disconnectsthe engine in a car from the rest of thedrivetrain, which cuts off the transfer of power to the wheels. When the clutch is released, theflywheel comes in contact with the engine's flywheel, and friction transfers torque to the drivetrainonce more.

When the driver pushes on the clutch pedal, a flywheel connected to the drivetrain is pulled awayand power to the wheels is cut off. The clutch allows shifting of gears in a car with a manualtransmission (or stick shift).

Give me an example!


68/73

Using a clutch to shift gears requires practice - especially if you want to do it smoothly! If you letthe clutch out too fast, the car will lurch forward - and sometimes the engine will die. But once youget the hang of it, using a clutch and shifting gears becomes second nature.

Efficiency

What is it?

Efficiency is the balancebetween the form of an object and its function. If the form of an object(like a building or a car) is well suited to its function, the that object is said to be highly efficient.

Give me an example!

Have you ever heard someone talk about cars in terms of fuel efficiency? A car that is designedto travel moremiles on a gallon of gasoline (or is rated at a highernumber of miles per gallon) ishigher in efficiency because it saves the driver money at the gas pump!

Energy


69/73

What is it?

Energy is matter which is vibrating at an extremely high rate. Energy has the capacity to dowork. Energy can take several forms - heat, elecricity, chemical, and mechanical, to name a few.

Give me an example!

Have you ever rubbed your hands on a fuzzy towel and felt the warmth? That heat is energywhich has been released by friction. Have you ever heard someone who is really tiredsay theyhave run out of energy? That means they feel like they feel too weakto do anything (or performany work).

Energy Transfer

What is it?

Energy transfer is when energy goes from one place to another -- or from one form to another.

Give me an example!

When you switch on an electric lamp, you make an energy transfer from the wiring system inyour house through the circuit in the lamp, which makes the lightbulb light up. In that sameexample, you are turning electric current (a flow of electrons) into light and heat energy as itpasses through the filament in the lightbulb -- another energy transfer!


70/73

Entropy

What is it?

Entropy is the scientific measurement of the change in the randomnessor disorderin a chemical

system as the result of a reaction. A positivechange in entropy means the system is lessordered after the reaction than it was before.

Give me an example!

Have you ever watched an ice cube melt at room temperature? You were watching entropy inaction! As the ice passes from a solid state to a liquid state, the level of entropy (or randomness)of the molecules rises

First Law of Thermodynamics

What is it?

The First Law of Thermodynamics states that the amount of heatenergy contained within aclosed system is always constant. This is the basis of the principle of conservation of energy.

Give me an example!

When a battery powered light is switched on and heat is produced, that heat energy actually


71/73

already existedinside the system as chemical energyinside the battery. So no energy is eithergainedor lostas a result of switching on the light.

Freezing Point

What is it?

When you take a liquid and reduceits heat content (or enthalpy) sufficiently, at some point it willturn into a solid. This is called freezing the liquid. The temperature at which this occurs is thefreezing point. Different substances have different freezing points.

Give me an example!

The freezing point of water is 32 degrees Fahrenheit (or 0 degrees Celsius). That's whygardeners watch the weather report to see if overnight temperatures are predicted to dip belowfreezing, or 32 degrees. That's when they cover up their prize plants to protect them!

HOOKES LAW

Hookes Law - Strength (Mechanics) of Materials

Mechanics of Materials Table of Content

Hookes Law - If a metal is lightly stressed, a temporary deformation, presumably permitted by anelastic displacement of the atoms in the space lattice, takes place. Removal of the stress resultsin a gradual return of the metal to its original shape and dimensions. In 1678 an English scientistnamed Robert Hooke ran experiments that provided data that showed that in the elastic range ofa material, strain is proportional to stress. The elongation of the bar is directly proportional to thetensile force and the length of the bar and inversely proportional to the cross-sectional area andthe modulus of elasticity.


72/73

Hooke's experimental law may be given by:

Where:

P = force producing extension of bar (lbf)

= length of bar (in.)

A = cross-sectional area of bar (in.2)

d = total elongation of bar (in.)

E = elastic constant of the material, called the Modulus of Elasticity, or Young's Modulus (lbf/in.2)

The quantity E, the ratio of the unit stress to the unit strain, is the modulus of elasticity of thematerial in tension or compression and is often called Young's Modulus.

Tensile stress, or simply stress, was equated to the load per unit area or force applied per cross-sectional area perpendicular to the force measured in pounds force per square inch.

Tensile strain, or the elongation of a bar per unit length, is determined by:

For the equations described above we may adequately expressed by Hooke's Law for elasticmaterials. For materials under tension, strain (e) is proportional to applied stress s.


73/73

Where:

E = Young's Modulus (lbf/in.2)

s = stress (psi)

e = strain (in./in.)

basic engineering book

Documents