CV Carburetor ....explained perfectly

How a carburetor works, schemes and explanations

2 stroke outboard Vrs. 4 stroke outboard

> Difference between #pressure and #velocity

 > Difference between #pressure and #velocity

You hold a water hose in your hand. Turn on the faucet and watch the water coming out of the hose. If you place the palm of your hand over the open end of the hose, you can feel the force of the water hitting the palm of your hand.
Pressure = Force ÷ area

You are feeling the force that the water is exerting on a specific area of your skin. As the water collides with your skin, the water’s velocity will decrease to 0 m/s. Your skin exerted a force on the water that caused the water to decelerate.

So, pressure measures the force that the water exerts on hole at the open end of the hose.
I have an attachment on the hose to decrease the area of the open end of the hose. As I decrease the area, the water’s velocity increases.

Velocity measures the distance that the water moves each second. Pressure supplies the force that caused the water to have enough kinetic energy to move that distance each second.

How a Car's A/C System Works - A/C Pro

DIFFERENCE BETWEEN TURBOSCHARGER AND SUPERCHARGER

There are key differences between a Turbocharger and a Supercharger. Many cars came from the factory with them, Mitsubishi, Saab, Audi, Volkswagen, Mercedes, Ford, Chevrolet and Nissan are all manufactures that do. Chances are, if your car came with one, you've wondered what they do and what the differences between the two are. Whether or not you've got a diesel powered or gasoline powered engine, companies such as Garrett, Holset, Mitsubishi and Borg Warner lead the way with factory forced induction applications. 

To understand the difference between the two, it is important to know the function of a turbocharger and a supercharger.  Both are forms of forced induction.  Both force air into the engine to achieve what we all want and crave – more power. 

The supercharger can be powered by a belt, gear, shaft, or chain.  There are quite a few different types of superchargers but the take-away point is this – a supercharger is connected to the crankshaft.  Meaning, a supercharger is always driven by the car’s engine.

A turbo does the same job as the supercharger – force more air into the car’s engine to make more power.  However, a turbo uses a turbine and is NOT connected to the crankshaft.  Instead of the engine, the turbo gets driven by the car’s exhaust gases.

The advantages and disadvantages are obvious.  Supercharger, being attached at the crankshaft, equals less efficiency – more fuel to power it.  With a turbo, you don’t affect efficiency because it is exhaust driven – no additional stress on the engine.  However, you deal with turbo lag.  With a supercharger, you get the benefits of forced induction from the very beginning.  With turbo, you have to wait til it “kicks in.”

It is important to note advances in both supercharger and turbo technologies are making great progress.  New turbos have all but eliminated turbo lag and there are highly efficient superchargers on the market as wel

SUPERCHARGER CUTAWAY

TURBOCHARGER CUTAWAY 

 https://www.youtube.com/watch?v=_vaw5zwnhrA 

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common material basics from mikecurtis check their website

List of Common Materials        source:http://www.mikecurtis.org.uk/ks2_materials.htm

:

---

SUBSTANCE	Description	USE/PROPERTY
Iron	Grey metal	Cheap and strong but rusts easily. The only magnetic metal.
Sulphur	Yellow solid	Soft and crumbly. Burns to make a gas with a chocking smell.
Brass	Yellow metal	An ALLOY of copper and zinc. Used to make water taps. (Often covered with a shiny layer of CHROME metal)
Copper	Pink Metal	Used to make water pipes and electric wires.
Mercury	Grey metal	The only liquid metal. Very heavy and very poisonous. Used by dentists for 'fillings'.
Aluminium	Pale grey metal	Low density (very light). Used to make saucepans and kitchen foil.
Gold	Yellow metal	Very heavy precious metal. Does not corrode. Used for jewellery and electrical contacts.
Perspex	Colourless, transparent	Often used instead of glass as it is strong and light but scratches and melts easily.
Glass	Pale green, transparent	Very hard (does not scratch easily) but easy to break.
Zinc	Grey metal	Plated over iron to stop it rusting (called GALVANIZED iron and is used for buckets, water tanks)
Lead	Grey metal	Soft and bendy. Melts easily. Used on roofs. Used to used in pencils.
Tin	Grey metal	Placed in a very thin layer on the inside of 'tin' cans to stop the iron going rusty.
GMaterials can be placed into groups:       Metals Shiny, conduct electricity and heat, strong, often heavy Girders, Bicycle frames, Electric wires, Tools, Saucepans and good quality cuttlery. Ceramics Substances made from pottery. They have been 'fired' at some stage in their manufacture. They look attractive, do not burn or melt but are usually brittle and break easily Tiles, kitchen plates, good quality cups Plastics Plastics usually melt or burn easily,. They are not very strong but can easily made into different shapes. They arecheap to produce and are good electrical insulators Washing up bowls, covering to electric wire, plugs, cheap cuttlery, containers for food Glass :Glass looks attractive and can eaily be made into different shapes. Transparent, Is not effected by liquids. Brittle but hard. (Breaks easily but will not easily scratch) Windows, mirrors, glasses, bottles Wood Cuts easily and can be polished so it is shiny. Looks attractive Furniture, building materials	Grey /black solid	Formed from carbon. Used in pencils instead of lead (which is poisonous). Properties of materials A property of a material is something about it that we can measure, see or feel Examples of different properties Strong Weak Heavy Light in weight Rough Smooth Shiny Dull Hard Soft Flexible Brittle Magnetic Non-magnetic Transparent Opaque Conduct electricity Electrical insulator Conductor of heat Thermal (heat) insulator Burns when heated Does not burn Melts easily  Does not melt easily

Difference between hardness and toughness

Difference between hardness and toughness: 

Toughness describes how much total energy has to be used before a material breaks. If the material takes a lot of energy (it may change shape) before breaking, then it is a tough material. If only a little energy is needed to break the material it is weak or brittle


Hardness describes how much energy it takes to deform (stretch, compress, bend, etc.) a material. If the material takes a lot of energy to change only a little, it is said to be hard. Conversely, if only a little amount of energy is needed to make a lot of shape change, then the material is soft. Metals would be considered hard, chewing gum would be soft. source:
http://www.newton.dep.anl.gov/askasci/mats05/mats05189.htm

cam mechanicsm

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The Impulse-Momentum Theorem

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MAKE presents: The Capacitor

MAKE presents: The Capacitor

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engine-notes

    
The Internal Combustion Engine (IC Engine) is a heat engine that converts chemical energy of fuel into mechanical energy. 
Chemical energy of a fuel is first converted into thermal energy by means of combustion with air inside the engine.  This thermal energy is again converted into useful work through mechanical mechanism of the engine. 
Most of the IC Engines are reciprocating engines having piston that reciprocate back and forth in cylinders within the engine.

*IC ENGINE COMPONENTS: 

The main components of a four stroke cycle engine are cylinder, piston, connecting rod, piston rings, cam shaft, crank shaft, inlet and outlet valves, fuel injector, cylinder head, push rod, cam follower, valve spring, big end bearing, etc.,.
The IC Engine used in heavy vehicles like bus is six cylinder four stroke diesel engine.
The piston reciprocates inside the cylinder.  Piston rings are inserted in the circumferential grooves of the piston.  The cylinder and cylinder head are bolted together.
The reciprocating motion of the piston is converted into rotary motion of the crankshaft by means of a connecting rod and crank.  The small end of the connecting rod is connected to the piston by a gudgeon pin or piston pin.  The big end of the connecting rod is connected to the crank pin.

*Cylinder Block:

*It is the main body of an engine which contains cylinders.
*The piston reciprocates inside the cylinder to develop power.
*The cylinders are accurately finished to accommodate pistons.
*During combustion, high pressure and temperature will be developed inside the cylinder.
*It is made of grey cast iron.
*The cylinder block is provided with water jackets for circulation of cooling water in     water cooled IC Engines.

Reconditioning:
*Reconditioning of cylinder block (or) an engine is needed above running over 5 lakhs kilometer.  In cylinder block, diameter of cylinder is checked for locality.  If needed boring is done.

Cylinder Head:
*The cylinder head is bolted to the top of the cylinder block.  It houses the inlet and exhaust valves through which the charge is taken inside of the cylinder and burnt gases are exhausted to the atmosphere from the cylinder.  It also contains fuel injector and cooling water jacket.  The materials used for cylinder heads are cast iron.


Crank Case:
*It may be cast integral with the cylinder block.
*It supports the crankshaft and camshaft with the help of bearings.
*It is also made of cast iron.

Oil Sump or Oil Pan:
*Oil Sump is fitted at the bottom of crankcase by using gasket.
*It contains lubricating oil.
*A drain plug is provided to the oil sump to drain out the oil.
*It is made up of pressed steel sheet. 
Reconditioning:
*Oil Sump is checked for cracks to avoid leakage.

Piston:

*It is a cylindrical shaped mass that reciprocates inside the cylinder.

*The top of the piston is called as crown and sides are called as skirt.

*It has grooves to hold piston rings and oil ring.

*It is opened at the bottom end and closed at the top.

*Piston is made of cast iron, aluminium alloy, cast steel.

*The firing order for HINO Engines which are used in BS1, BS2, BS3 are 1-4-2-6-3-5

*The main function of the piston are

*To transmit the force by explosion to the crankshaft.

*To form a seal, so that the high pressure gases in the combustion chamber do not escape into the cylinder.

*To serve as a guide and a bearing for small end of the connecting rod.

Reconditioning:
*Check for cracks in piston and make another groove on the top.
*Grooves are to stop the pressure leakage.

Piston Rings:

Fig.2.4. Compression Ring and Oil Ring
*They are used to maintain air tight sealing between piston and cylinder to prevent gas leakages.
*Piston rings are fitted in the grooves which are provided in the top portion of the piston skirt.
*There are two types of piston rings used in a piston.  They are
Compression Ring:
*These rings provide an effective seal for the high pressure gases inside the cylinder.  Each piston is provided at least with two compression rings.

Oil Ring:
*These rings wipe off the excess oil from the cylinder walls.  It also returns this excess oil to the oil sump through the slots provided on the rings.  Piston rings are generally coated with Chromium or Cadmium.


Connecting Rod:


*It is used to connect the piston and crankshaft with the help of bearing.

*It is usually in I-Section.

*Its small end is connected with the piston by the piston pin and its big end is connected to the crank by the crank pin.


Crankshaft:

*It is used to convert reciprocating motion of the piston into rotary motion.  The crankshaft can be held in position by the main bearings.

*Flywheel is mounted at the rear end of the crankshaft.
Counter Weights are provided to keep the system in perfect balance.



Reconditioning:
*For HINO Engine, standard diameter for connecting rod journals is 61.95 mm.  In reconditioning, it can be reduced upto 60.95 mm by (0.25+0.25+0.25+0.25) four times.

*Fillet radius also reduced.  This process is done by special grinding machine.

*The cracks are checked by using ultraviolet ray machine.
                                       
Camshaft:  



      *It is used to convert the rotary motion of the camshaft into linear motion of the follower.

*It operates the inlet and exhaust valves through rocker arms.

*It has so many cams as the number of valves in an engine.

*It is rotated at half of the speed of the crankshaft.


Engine Valves:
*Valves are used for closing and opening passage of the cylinder.
*There are two valves in an engine cylinder namely inlet and exhaust valves.
*Valves are operated by cam and rocker arm mechanism.
*Inlet Valves are larger than the Exhaust Valve.
*Valve face angle is generally kept 45⁰ or 30⁰.

COOLING SYSTEM:
*Cooling system reduces the heat of the engine.

Coolant:
*Coolant is an oil based liquid used in the water cooling system
*It acts as a cooling medium.






Radiator:

*Water cooling system is called as Radiator.  In this system engine cylinders are surrounded by water jackets through which the cooling liquid flows.
Heat transferred from the cylinder walls into liquid. The liquid goes to the radiator where the liquid losses its heat by the air.

Reconditioning:
*While reconditioning the leakage should be checked. 
*If any leakage that should be welded or the tube should be blocked.

Water pump:
*A pump is necessary for the forced circulation of engine cooling System.  
The pump is mounted at the front end of the engine and is driven by crank-shaft through a ‘V’ belt.

LUBRICATION SYSTEM:
For the friction free running of inner part of the engine, lubrication system plays a vital role.  If friction increases the temperature of the engine also increases.  So, the lubrication system is installed. There are two types of lubrication system. They are as follows:

Splash System:
A Scoop is made in the lowest pall of the connecting rod and oil is stored in the oil pump.



Pressure System:
In pressure system, an oil pump takes oil from the pump through a strainer and delivers through the strainer and filter to the main oil gallery at a pressure of 200 to 400 kPa.


FUEL SUPPLY SYSTEM:
The fuel supply is done through fuel injection pump.

Fuel Injection Pump:  

The function of the fuel injection pump is to deliver accurately metered quantity of fuel under high pressures at the correct sequence, to the injector(nozzle) fitted on the each cylinder.  The injection pressure generally employed in case of automotive fuel injection range from 7 to 30 MPa.  In some systems injection pressures can be as high as 200mpa 

Reconditioning:
The filters are thoroughly cleaned. If any wear the filter should be changed.
The casing should be checked for any cracks.

Fuel Injector:
This is also known as nozzle, atomizer or fuel valve.  Its function is to inject fuel in the cylinder in properly atomized form and in proper quantity.


STORAGE BATTERIES:  
Storage battery is perhaps the most important comport of the on tire electrical system of a vehicle.
It gives power to the starting motor. Also it gives power to all electrical system when engine is in off condition.  The different parts in the batteries are as follows:
Container
Separators
Cell covers
Electrolyte (dil.H2SO4)
In buses, two 12V Batteries are connected in series to get 24V. 

Reconditioning:
By adding electrolyte in an exact dilute condition and check the separator condition and plate’s effectiveness.

STARTING MOTOR (SELF-MOTOR):
Starting motor used to give initial rotating moment to the fly wheel. Thus engine gets started. 
When given positive and negative of battery actuates the armature,  the armature starts rotating and when self-button is pressed, there is signal along the solenoid section which indulge in proper & horizontal motor until the time of the button release time.
When the flywheel starts rotating, the pinion from the self-motor disengage from the flywheel.

ALTERNATOR:
Alternator gets rotary moment from crank-shaft by means of ‘V’ belt.
It gives current to electrical system while engine running.
The battery charged with the current from alternator.
Alternator is a device which is used to convert mechanical energy to electrical energy where DC to AC Conversion takes place.
When the self button is pressed the self-motor starts which gives a slight rotation to the flywheel which in turn connected to the crankshaft of the engine gets rotated.
So the alternator at 1 side gets rotated & produces the DC out.

TRANSMISSION SYSTEMS:
Clutch:
Clutch is a mechanical arrangement which is used to engage and disengage the drive shaft and driven shaft.

Parts:
Fly wheel
Pressure plate
Clutch plate
Clutch spring

Reconditioning:  
The pressure plate fingers are chance to get wear.  So by grinding or metal adding the same depth is maintained in all fingers.
Clutch plate liners are changed.

Gear box:
When the gear is changed through the gear lever, it transmits the motion to the gear box through linkages.
According to the change in gear, the corresponding sliding dog moves and attach with the gear. 
Now the speed ratio changes and correct torque will be gained through the gear box.
The main functions are
At low speeds, the torque produced by engine is very small, which increases with increase of speed peaks at some optimum speed and starts decreasing beyond that.
The transmission also provides a neutral position.
It gives reverse rotation.

Types:
Sliding mesh gear box
Synchromesh gear box
Constant mesh gear box

Reconditioning:
Check all the teeth if there is any broken teeth.
Check the bearing.
Check main shaft teeth.
If any breakages that should be changed.

Propeller Shaft: 
This shaft is transmits the drive from the transmission to the level pinion or worm of final drive in front engine, rear drive vehicles and from the transfer box to the front and rear axles in all wheel drive vehicles.
Parts:
Shaft
Universal joints
Slip joint
Reconditioning:
The universal joint cross kits should be changed.
Bending of shafts should be checked failure bearings should be change.

FRONT AXLE AND STEERING:
Primary function of the steering is to achieve angular motion of the front wheels to negotiate a turn.
Front axle is a dead axle, in four wheel drive vehicles it is live axle.
In right side of the front wheel, the Track Liner is connected.  It is connected 

Bet
 ween the sub-axle and the steering.
Tie Rod is one of the mechanical linkage which is connected above the front axle, which is used to turn the front set of wheels, when right wheel is turned by the action of steering.

Reconditioning:
In power steering system teeth of the steering gears should be changed
There should be checks for leakages.
In ordinary rotary valve type steering systems, rotary balls should be changed
The bearing guide should be checked.
King pin should be checked for any deformation which connects the front axle with the sub axle.
Socket is cleaned and the tooth is checked.

BRAKES:
The brakes are  used to stop the vehicle which in motion
When the driver applies the brake, the brake lever actuate the leak valve.
It actuate the air cylinder.
The compressed air from the air cylinder is passed to the brake chamber.
In Brake Chamber, by the pressure of compressed air, the diaphragm is pushed against the concentric spring force.
Now, the push and pull rod extends from the brake chamber which is connected with the slock adjuster.
The slock adjuster actuate the brake shoe to expand towards outer which is kept inside the wheel drum.  Thus the air brake is applied.
Hand Brake or Parking Brake is only available on the rear set of wheels.

Reconditioning:
Brake shoe checked for shearing and cracks.
The retracting spring thickness should be checked.
Brake lining is changed as per the condition of wear.

DIFFERENTIAL ARRANGEMENT:
When the bus is taking a turn, the outer wheels will have to travel greater distance compared to the inner wheels in the same time.
The differential should reduce the speed of inner wheels and increase the speed of outer wheels when taking turns.
This arrangement is kept in the rear axle.  Propeller Shaft drive the differential gear.

Parts:
Crown Wheel
Bevel Pinion
Sun Gear (2 nos)
Star Gear (4 nos)
Cross or cage


     Reconditioning Advantages:
It increases the life of the vehicle.
It reduces the cost.
It is a well economic process.
Cost of operation is less.

TYRE REBUTTONING:
The tyre which is weared is re-button in this section.
Initially the tyre is undergone Buffing Process.
New Tyre - 21⁰ angle
1st Re-buttoning Tyre - 20⁰ angle
2nd Re-buttoning Tyre - 19⁰ angle
Radial Tyre - 22⁰ angle
Next, the Bonding Vulcanizing Cement is coated over tier.
Bonding Gum is used to join the button sheet and weared tier.
Then, it is covered by a protective cloth and enclosed in an envelope.
Then tyre is boarded into a pressure chamber which is maintained above 125⁰ C for 2 hours.
After 2 hours, the tyre is taken from the chamber which is re-buttoned.

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Education in tamilnadu

                                     EDUCATION IN TAMILNADU 
                                                                                                                      There are totaly 592 affliated engineering colleges in tamilnadu.The seats are filled on the basis of cutoff (physics,chemistry,mathematics).Once after hsc examination there was entrance exam for undergraduate courses, but it has been cancelled.Due to this cancellation,most of the schools have started skipping 11th standard and started focusing on 12th standard to get good results.Duration of study for a single exam is now 2 years of study thereby it is easy for any school's to produce good result.Some districts like namakal,kanyakumari,tirunelveli are dependent on this.As far as I gathered ,from a reputed school in namakkal (rasipuram), students are been highly stressed ,to get a clear idea of what Iam talking chk this video link  https://www.youtube.com/watch?v=6X8a0igR1Lk .Students are not made creative,they are made to memorize their books,the beauty of physics ,chemistry ,the universal language maths are taught in the wrong way.Students who get good marks ie)above 450 in 10th standard ,and district toppers are given open offers to join their schools by making them believe that by joining their schools those students can produce good cutoff in 12th and so they can enter CEG campus or medical colleges.Since the competition is high,students as well as parents are also trapped in this net.These schools do produce higher results.  

 REASONS

1.Most of the schools finish their 11th standard portion just for some record sake some schools even don't commit that one.

2.coaching after the schools are over upto 6/8 

3.coaching in morning 6-8 o clck

4.2 years of study
5.frequent cyclic tests/model tests /notes/important questions


                                                                                        6.even questions asked in exams are    very much frequently  repeated and can be guessed  --------will be continued

GEAR BASICS

gear transmission

Download engineering terms.pdf

Download engineering terms.pdf

Enthalpy: Crash Course Chemistry #18

BASIC ELECTRIC CONCEPTS

The concepts of voltage and current are not easy to explain. Both properties are invisible to the human eye, and work in ways that are counter-intuitive. The only reasonable means with which to explain the properties of electric voltage and current would be to relate it to more visible, everyday terms, such as the flow of water in pipes. Most people have used come type of faucet or plumbing fixture in their lifetimes, and therefore can visualize water flowing from some form of piping or valve. Another general means of conceptualize the flow of water would be a river or stream. This flow of water is often referred to as the stream (or pipe’s) current, which analogous to the current flowing in an electric wire. Just as in an electric wire, the bigger the pipe, the more water that can flow through it, so the more current the pipe can allow. The comparison holds up so well that even the amount of resistance from the size of the pipe can be related to the resistivity of the electric wire. Electric current is measured in Amps, or Amperes everywhere across the globe.

Voltage is somewhat more difficult to conceptualize. Electric Voltage in the past and still throughout modern industries is referred to as “electric potential” or “electro-motive force.” Much like the force of gravity pulls water down pipes or mountainsides, this “potential” of electricity causes electric current to flow through wires from higher to lower voltage. Therefore, voltage can be somewhat conceptualized as analogous to the vertical drop with which water traverses in a waterfall or through plumbing. The higher the voltage, the higher the waterfall (or water tower). Since the pressure of the water in plumbing is directly proportional to the height of the water tower, it is also correct to conceptualize electric voltage to being analogous to the pressure of the water within the pipes as well.

With electrical applications, power is simply the voltage of the wire multiplied by the current running through it. In the analogous plumbing terms, it’s easier to think of it as the amount of water falling by the distance it fell. Kind of like the area of a waterfall…a short but wide waterfall might have the same power output as a narrow but tall waterfall. Naturally, a waterfall that was both tall and wide would have higher power output than the previous two mentioned. The exact same rules apply for the voltage and current of an electric circuit.

Resistance is somewhat tricky to describe in terms of a water-analogy. The resistivity of the pipes themselves matches well with electrical wiring; so in essence, the electrical component of a resistor can be seen analogous to a section of smaller pipe inserted into an otherwise thicker pipe of water. This smaller section causes back-pressure on the water-line, causing the overall current in the pipe to drop by a certain amount. The higher the resistance, the smaller the pipe. This is exactly the same as how electrical current responds to a resistor in a wire. With electrical wiring, the amount of current passing through a wire is dependent on the voltage of the electricity applied to the wire as well as the resistance of the load or resistor placed in the circuit. This relationship is known to the Electrical Engineering community as Ohm’s Law, which states that: the current between two points on an electrical circuit is proportional to the voltage difference across those two points. An image of this relationship is shown below.

The last major concept to cover in terms of electricity is the diode, or one-way valve for electricity. Without focusing too much on the details of a diode’s construction, it’s a component that only allows current to flow in a single direction through it. Essentially, the mechanism for which this accomplished is very similar in concept to a waterfall. An intrinsic potential voltage is created within the component’s material itself, creating somewhat of a “ledge” that electric charge can flow across from higher-to-lower potential. However, just like in a waterfall, the charge is not able to flow from a lower ledge to a higher one. While the mechanism for which this accomplished is done through semiconductors, the fundamental concepts still hold true throughout the analogy between water and electric charge.

http://sargosis.com/articles/science/intro-guide/basic-electric-concepts/

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Thermodynamics: Basic Terms

Thermodynamics:  The branch of science that deals with the study of different forms of energy and the quantitative relationships between them.

System:  Quantity of matter or a region of space which is under consideration in the analysis of a problem.

Surroundings:  Anything outside the thermodynamic system is called the surroundings. The system is separated from the surroundings by the boundary. The boundary may be either fixed or moving.

Closed system:  There is no mass transfer across the system boundary. Energy transfer may be there.

Open system:  There may be both matter and energy transfer across the boundary of the system.

Isolated system:  There is neither matter nor energy transfer across the boundary of the system.

State of the system and state variable:  The state of a system means the conditions of the system. It is described in terms of certain observable properties which are called the state variables, for example, temperature (t), pressure (p), and volume (v).

State function:  A physical quantity is a state function in the change in its value during the process depends only upon the initial state and final state of the system and does not depend on the path by which the change has been brought about.

Macroscopic system and its properties:  If as system contains a large number of chemical species such as atoms, ions, and molecules, it is called macroscopic system. Extensive properties: These properties depend upon the quantity of matter contained in the system. Examples are; mass, volume, heat capacity, internal energy, enthalpy, entropy, Gibb's free energy. Intensive properties:  These properties depend only upon the amount of the substance present in the system, for example, temperature, refractive index, density, surface tension, specific heat, freezing point, and boiling point.

Types of thermodynamic processes:  We say that a thermodynamic process has occurred when the system changes from one state (initial) to another state (final).

Isothermal process:  When the temperature of a system remains constant during a process, we call it isothermal. Heat may flow in or out of the system during an isothermal process.

Adiabatic process:  No heat can flow from the system to the surroundings or vice versa.

Isochoric process:  It is a process during which the volume of the system is kept constant.

Isobaric process:  It is a process during which the pressure of the system is kept constant.

Reversible processes:  A process which is carried out infinitesimally slowly so that all changes occurring in the direct process can be exactly reversed and the system remains almost in a state of equilibrium with the surroundings at every stage of the process.

Exothermic Process:

Process that releases heat to its surroundings.

Energy:

Capacity for doing work or supplying heat

Calorie:

Quantity of heat needed to raise the temperature of 1 gram of pure water by 1 degree C

Conversion used to go between calorie and joule

4.184 J=1 calorie

SENSIBLE HEAT VS LATENT HEAT

Two forms of heat are relevant in air conditioning:

• Sensible heat
• Latent heat

Sensible heat

When an object is heated, its temperature rises as heat is added. The increase in heat is called sensible heat. Similarly, when heat is removed from an object and its temperature falls, the heat removed is also called sensible heat. Heat that causes a change in temperature in an object is called sensible heat.

Latent heat

All pure substances in nature are able to change their state. Solids can become liquids (ice to water) and liquids can become gases (water to vapor) but changes such as these require the addition or removal of heat. The heat that causes these changes is called latent heat.

Latent heat however, does not affect the temperature of a substance - for example, water remains at 100°C while boiling. The heat added to keep the water boiling is latent heat. Heat that causes a change of state with no change in temperature is called latent heat.

Stress on an Inclined Plane.MP4

Stress on an Inclined Plane.MP4

Why Mohr's Circle - Brain Waves.avi

lower centre of gravity -application

Every single body and thus the athletes themselves, is made up of individual components each of which has its own weight. So our weight is just the sum of individual weights, of components such as our arms, legs, etc. The point, about which the distribution of these individual weights is symmetrical, is the center of gravity of the body. Thus, if a body has more mass distributed in its upper part, the center of gravity will be closer to the top of the body. This applies to humans, as the center of gravity of an average person is located approximately at a height of one meter, thus being above the waist

There are two properties of the center of gravity that have a great impact on sport. First of all its location is dependent on the shape of the body. So if the same body is to take a different shape, the position of the center of gravity will shift. An athlete that bends his/her legs will lower his/her center of gravity position. This, amongst other things, will result in greater stability, something especially important in sports such as wrestling. Also, and this may sound the strangest, the center of gravity can lie entirely outside the body itself. For example, if the body is hollow it will literally be positioned somewhere in the air. During the Olympic Games in Mexico, in 1968, an, until then unknown athlete, the American Dick Fosbury, came from nowhere to teach the world about both of these properties.

The truly ingenious leap (!) in the technique was that by clearing the bar with his back and by changing the shape of his body, the athlete could clear the bar without his center of gravity having to also clear it. By this change in body shape he was able to move his center of gravity outside his body. The energy required for a jump depends on the maximum height of the center of gravity and so by lowering its position one also lowers the energy required to clear the bar 

structural basics-centre of mass ,centre of curvature , stable ,unstable,neutral equilibrium

Centre of mass and centre of curvature source:http://www.mace.manchester.ac.uk/project/teaching/civil/structuralconcepts/Statics/mass/mass_mod7.php chk this website guys a lot of useful stuff and very very useful

This demonstration shows the relationships between the three states of equilibrium and three relative locations of the centres of mass to the centres of curvature of bodies.

      
a.                                            b.
Figure 2.A1: The models

Figure 2.A1 shows four small aluminum axially symmetric objects that have different dimensions and different relative locations of their centres of mass to the centres of curvature (The centre of curvature of a curve at any point is the centre of the circle which is tangent line at the point on the curve. If a line is drawn perpendicular to the curve at the point, the intersection point of the line and the vertical axis of symmetry is the centre of curvature):

    a. A round ball: The centre of mass and the centre of curvature of the ball are at the same point, the centre of the ball.

    b. A circular solid cylinder attached to a small part of a solid sphere: The centre of mass of the object is lower than the centre of curvature at any point on the spherical surface.

    c. A circular solid cylinder attached to a half of a solid sphere: The centre of mass of the object is higher than the centre of curvature at any point on the spherical surface.

    d. A hollow circular cylinder attached to a small part of a solid sphere: The centre of mass of the object is lower than the centre of curvature at any point on the spherical surface.

An experiment may be conducted as follows:

    a. Applying a small lateral force on the ball causes it move from its original equilibrium position (Figure 2.A2a). It moves to a new position and a new state of equilibrium (Figure 2.A2b). The original state of equilibrium is a position of neutral equilibrium.

      
a. Initial position of the ball                       b. New position of the ball
Figure 2.A2: Neutral equilibrium

    b. Applying a lateral force on the top of the object (b) rotates the object as shown in Figure 2.A3a. Releasing the force, the object returns to its original equilibrium position (Figure 2A3b). The original state of equilibrium is a position of stable equilibrium.

      
a. Object (b) with applied lateral force                       b. Object (b) returns to its original position
Figure 2.A3: Stable equilibrium

    c. Allying a force on the top as above but object (c) of the third object and holding it to the position from its original equilibrium position as shown in Figure 2.A4a. When the finger is removed the object falls over as shown in Figure 2.A4b. This original state of equilibrium is a position of unstable equilibrium.

      
a. Object (c) with applied lateral force                       b. Object (b) Object (c) topples over
Figure 2.A4: Unstable equilibrium

    d. Applying a lateral force on the top of object (d) to the position shown in Figure 2.A5a. When the force is removed, the object moves back to its original position. The original state of a position of stable equilibrium.

      
a. Object (d) with applied lateral force                       b. Object (d) returns to its original position
Figure 2.A5: Stable equilibrium

It is observed from this demonstration that the states of equilibrium relate to the relative positions of the centres of mass to the centres of curvature of bodies:

• If the centre of mass and the centre of curvature of a body are at the same point, the body is in a state of neutral equilibrium.
• If the centre of mass is lower than the centre of curvature of a body, the body is in a state of stable equilibrium.
• If the centre of mass is higher than the centre of curvature of a body, the body is in a state of instable equilibrium