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mnemonic pdf for memorising maxwell equations in thermodynamics

on_MRS_Thermodynamic_Mnemonic.pdf

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Thomas Suarez: A 12-year-old app developer

Ultrasonic welding

Ultrasonic welding

Ultrasonic welding

Ultrasonic welding

Transfer Molding

Blow molding

Thermit welding used to join Railway tracks - Dragonfly Education

TIG Welding Aluminum Basics 4: Introducing Filler Metal to the Puddle

Resistance Spot Welding - How It Works

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Plasma Arc Welding

beautiful enginering pics

Matter Song

The NEW Periodic Table Song (In Order)

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

structure basics for civil and mechanical

Centreofmassandstability source:http://www.mace.manchester.ac.uk/project/teaching/civil/structuralconcepts/Statics/mass/mass_mod5.php

This demonstration shows how the stability of a body relates to the location of its centre of mass and the size of its base.

       (a)                                                                      (b)        (c)                                                                      (d) Fig. 2-9: Centre of mass and stability of three aluminum blocks

Fig. 2-9a shows three aluminum blocks with the same height of 150mm. The square sectioned block and the smaller pyramid have the same base area of 29mm x 29mm. The larger pyramid has a base area of 50mm x 50mm but has the same volume as that of the square sectioned block. The three blocks are placed on a board with metal stoppers provided to prevent sliding between the base of the blocks and the board when the board is inclined. As the board is inclined, its angle of inclination can be measured by the simple equipment shown in Fig. 2-9b. Basic data for the three blocks and the theoretical critical angles calculated using Eq. 2-7 are given in Table 2-1. Theory predicts that the largest critical angle occurs with the large pyramid and the smallest critical angle occurs with the square sectioned block.

The demonstration is as follows:

1. The blocks are placed on the board as shown in Fig. 2-9 in the order of increasing predicted critical angle.
2. The left hand end of the board is gradually lifted and the square sectioned block is the first to become unstable and topple over (Fig. 2-9b). The angle at which the block topples over is noted.
3. The board is inclined further and the pyramid with the smaller base is the next to topple (Fig. 2-9c). Although the height of the centre of mass of the two pyramids is the same, the smaller pyramid has a smaller base and the line of action of its weight lies outside the base at a lower inclination than is the case for the larger pyramid. The angle at which the smaller pyramid topples over is noted.
4. As the board is inclined further the larger pyramid will eventually topple over but its improved stability over the other two blocks is apparent (Fig. 2-9d). Once again the angle at which the block topples is noted.

The angles at which the three blocks toppled are shown in Table 2.1.

Table 2.1 Comparison of the calculated and measured critical angles

Model	Cuboid	Small Pyramid	Large Pyramid
Height of the model (mm)	150	150	150
Height of the centre of mass (mm)	75.0	37.5	37.5
Width of the base (mm)	29	29	50
Volume ( )
Theoretical Max Inclination (deg.)	10.9	21.9	33.7
Measured Max Inclination (deg.)	10.0	19.0	31.0

The results of the demonstration as given in Table 2.1 show that:

• The order in which the blocks topple is as predicted by Equation 2.7 in terms of the measured inclinations and confirms that the larger the base or the lower the centre of mass of a block, the larger the critical angle that is needed to cause the block to topple.
• All the measured critical angles are slightly smaller than those predicted by Eq. 2-7.

Repeating the experiment several times confirms the measurements and it can be observed that the bases of the blocks just leave the supporting surface immediately before they topple, which makes the centres of the masses move outwards. In the theory the bases of the blocks remain in contact with the support surface before they topple.

This demonstration shows that the larger the base and/or the lower the centre of gravity, the larger will be the critical angle needed to cause the block to topple and that this angle is slightly less than that predicted by theory.

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The Bernoulli effect

The Bernoulli effect

#Structures-#tension-#compression-#stress

ENGINEERING GAMES http://engineering-games.net/

Taken With Webpage Screenshot    http://engineering-games.net/

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VISUALISING STRESS

Balloons on nails

This demonstration shows the effect of stress distribution.

      
(a)                                                                                  (b)
Fig. 6-1: Balloon on nails

Place a balloon on a single nail and hold a thin wooden plate above the balloon and position the balloon as shown in Fig. 6-1a. Gradually transfer the weight of the plate onto the balloon. Before the full weight of the plate rests on the balloon, it will burst. This happens because the balloon is in contact with the very small area of the single nail, resulting in very high stress and causing the balloon to burst.

Now place another balloon on a bed of nails instead of a single nail. Put the thin wooden plate on the balloon and add weights gradually onto the plate as shown in Fig. 6-1b. It will be seen that the balloon can carry a significant weight before it bursts. It is observed that the shape of the balloon changes but it does not burst. Due to its changed shape, the balloon and hence the weight on the balloon are supported by many nails. As the load is distributed over many nails the stress level caused is not high enough to cause the balloon to burst.

Fig. 6-2: A person lying on a nail bed

A similar example was observed at a science museum as shown in Fig. 6-2. A 6000-nail bed is controlled electronically allowing the nails to move up and down. When the nails move down below the smooth surface of the bed, a young person lies on the bed. Then the 6000 nails move up slowly and uniformly and lift the human body to the position shown in Fig. 6-2. If the body has a total uniform mass of 80kg and about two third of the nails support the body, each loaded nail only carries a force of 0.2 N or a mass of 20 grams. Thus the person is not hurt by the nails.

      
a) 49 plastic cups placed upside down                                   b) A person standing on the cups
Fig. 6-3: Uniform force distribution

A similar but simpler demonstration can be conducted following the observation of the nail beds. Fig. 6-3a shows 49 plastic cups which are placed upside down and side by side. Place two thin wooden boards on them and invite a person to stand on the boards. The boards spread the weight of the person, 650 N, over the 49 cups, each cup carrying about 13 N, which is less than the 19 N capacity of a cup. SOURCE:http://www.mace.manchester.ac.uk/project/teaching/civil/structuralconcepts/Statics/stress/stress_mod1.php

Experimental Stress Analysis Lab

Cavitation Demo.mp4

important symbols

Greek Symbol		Greek Letter Name	English Equivalent
Upper Case	Lower Case
Α	α	Alpha	a
Β	β	Beta	b
Γ	γ	Gamma	g
Δ	δ	Delta	d
Ε	ε	Epsilon	e
Ζ	ζ	Zeta	z
Η	η	Eta	h
Θ	θ	Thet a	th
Ι	ι	Iota	i
Κ	κ	Kappa	k
Λ	λ	Lambda	l
Μ	μ	Mu	m
Ν	ν	Nu	n
Ξ	ξ	Xi	x
Ο	ο	Omicron	o
Π	π	Pi	p
Ρ	ρ	Rho	r
Σ	σ	Sigma	s
Τ	τ	Tau	t
Υ	υ	Upsilon	u
Φ	φ	Phi	ph
Χ	χ	Chi	ch
Ψ	ψ	Psi	ps
Ω	ω	Omega	o

f

MAKE presents: Ohm's Law

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streamline flow of a fluid over a surface

Hydraulic Gradient Line And Total Energy Line- meaning

Hydraulic Gradient Line And Total Energy Line

Hydraulic Gradient Line And Total Energy Line

Hydraulic Gradient Line And Total Energy Line are the graphical representation for the longitudinal variation in piezometric head and total head.
Consider two points 1 and 2 in a pipe line having 'l' meters apart with the reference to this potential datum line,z1,p1/w and v1^2/2g represent datum head,pressure head,velocity head at section 1. similarly the corresponding values at 2.
The some of potential and pressure head.ie,[z+p/w] at any point is called the piezometric head.if a line joining the piezometric levels at varies points,the lines so obtain is called hydraulic gradient line (HGL)
The some of potential head,pressure head and velocity head is known as total head.
If a line joining the total heads at various points,the line so obtained is called total energy gradient line.

moment of inertia

Second moment of area (I)

The second moment of area is also known as the moment of inertia of a shape. It is directly related to the area of material in the cross-section and the displacement of that area from the centroid. Once the centroid is located, the more important structural properties of the shape can be calculated. The axis that determines the centroid is also known as the neutral axis (N/A).

The second moment of area is a measure of the 'efficiency' of a shape to resist bending caused by loading. A beam tends to change its shape when loaded. The second moment of area is a measure of a shape's resistance to change.

Certain shapes are better than others at resisting bending as demonstrated in the diagram. Clearly, the orientation of the shape also influences bending. 

WHAT IS THE DIFFERENCE BETWEEN STREBGTH AND STIFNESS?

General Concepts and Definitions



• Strength The ability to sustain load.
• Stiffness Push per move; the ratio of deformation to associated load level.
• Stability The ability of a structure to maintain position and geometry. Instability involves collapse that is not initiated by material failure. External stability concerns the ability of a structure's supports to keep the structure in place; internal stability concerns a structure's ability to maintain its shape.
• Ductility The amount of inelastic deformation before failure, often expressed relative to the amount of elastic deformation.



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Meanings at various levels of scale

Material

Strength Material strength is measured by a stress level at which there is a permanent and significant change in the material's load carrying ability. For example, the yield stress, or the ultimate stress.
Stiffness Material stiffness is most commonly expressed in terms of the modulus of elasticity: the ratio of stress to strain in the linear elastic range of material behavior.
Stability As it is most commonly defined, the concept of stability applies to structural elements and systems, but does not apply to materials, since instability is defined as a loss of load carrying ability that is not initiated by material failure.
Ductility Material ductility can be measured by the amount of inelastic strain before failure compared to the amount of elastic strain. It is commonly expressed as a ratio of the maximum strain at failure divided by the yield strain.



	Strength	Stiffness	Stability	Ductility
M a t e r i a l