Behavior of Materials in Tension

 Understanding the behavior of materials when loaded is a vital part of creating safe and reliable structures. Of the various stresses a given structural element may be subjected to, tensile stress is perhaps the most concerning. - Not that materials are necessarily always that much stronger in compression and shear, given an equal force per unit area.

It doesn't take a genius to see that beams are weaker to bending than columns are to buckling. This is due to the direction and position of the primary loads and not because of the material's tensile properties. This becomes apparent when both the beams and columns are of the same material, length, and cross section, yet the beams will exhibit major deflection long before the column comes even near buckling.

Due to this phenomenon, a beam must be carefully designed, with its second moment of area and material make-up ultimately deciding its resistance to deformation and failure. Rather than only tension, a horizontal structural member will more likely experience both tension on the upper face, and compression on the lower face, as it bends downward when loaded.

Stress-Strain Curve

Generally speaking, there are two kinds of material-types, ductile and brittle. By using a stress-strain curve one can graph the behavior of these materials starting from its original state to its point of rupture. Ductile materials will exhibit both an engineering or apparent stress-strain curve as well as a 'true' or actual stress-strain curve.

The difference is that the engineering curve bases its stress on the initial cross section of the material in question, whereas the true curve takes instantaneous ratios as the cross sectional area decreases due to Poisson's contractions. So with the engineering curve, the stress decreases with the decrease in cross section, whereas stress in the true curve will continue to rise.

Under normal test conditions, the true stress-strain curve is difficult to determine without continually monitoring the cross section. This is why the engineering curve is commonly used to make quick analysis of materials, even though the true curve is a better representation. As long as you don't get the two mixed up, they both have their individual pros and cons.

Strain-hardening and Necking

Ductile materials also exhibit a phenomenon called strain-hardening or work-hardening when its yield point has been crossed and it enters plastic deformation. As the stress increases due to the strain-hardening, it will eventually reach its ultimate strength, at which point it will begin necking.

Necking is when the material's cross section begins decreasing rapidly in a localized point, as opposed to a uniform decrease across the entire member. Once a member begins necking, rupture will soon follow. Necking is strictly a property of ductile materials, as opposed to brittle materials which will fracture before displaying any major cross-sectional reduction.

Brittle materials do not exhibit the discrepancy between true stress-strain and engineering stress-strain, as they neither have a yield point nor strain-harden. What this means is that the stress-strain curve of brittle materials will be linear, and extend in a linear fashion right up to their point of rupture. There is no yield point where the stress decreases, and no necking after ultimate strength.

Testing A Scientific Hypothesis

It is fair to say that scientists are like detectives. They piece together clues to learn about a process or event. One of the ways scientists collect evidence or clues is by conducting experiments. Experiments test an idea or hypothesis. Although all experiments do not follow the same step-by-step instructions, many do follow a similar investigation procedure.

Experiments begin by posing a question. A scientific question is one that can be answered by gathering evidence. For example, the question, "Which freezes faster - fresh water or salt water?" is scientific question because it can be answered by carrying out an investigation and gathering information.

The next step is to develop a hypothesis. This is a prediction about an experiment outcome. A hypothesis is a type of prediction, meaning it is formulated using observations and previous knowledge and experience. However, a hypothesis differs from a prediction in that it must be testable to prove or disprove fact. A properly worded hypothesis should take the form of an "if...then" statement. For example, "If I add salt to fresh water, then the water will take longer to freeze." Hypothesis statements can be used as a rough outline for conducting an experiment.

Next, the scientist must design an experiment in order to test his or her hypothesis. The plan should be written out in a step-by-step procedure and should describe the details of the observations and measurements. When designing the experiment, there are two important steps that must be included: controlling variables and forming operational definitions.

A variable is any factor that can change in an experiment. A single variable that can be changed throughout the experiment is called the manipulated variable. Using the example above, the manipulated variable is the amount of salt added to the water. The responding variable is what you measure or observe to obtain your results. Using the same experiment, "how long the water takes to freeze" is the responding variable.

The other component of a well-designed experiment is having clear operational definitions. An operational definition is a statement that describes how a particular variable is to be measured or how a term is to be defined. How will you determine if the water has frozen? Insert a stick in each container. What is the definition of "frozen" in relation to the experiment? This is the time at which the stick can't move anymore.

The observations and measurements made in an experiment are called data. At the end of each experiment, data should be analyzed for patterns and trends. Patterns are better revealed when they are classified in tables or graphs. They can then help the scientist answer questions like: Did they support the hypothesis? Do they reveal flaws in the experiment? Is more data needed?

After a thorough analysis, a conclusion must be made to sum up the investigation. When drawing a conclusion, the scientist needs to decide whether the data collected supports his or her hypothesis. Sometimes, it takes several experiments before a definitive conclusion can be made. Often, conclusions lead to posing new scientific questions and planning different experiments, while using the same investigation procedure to test a new hypothesis. If doing experiments seems like an exciting activity, you may want to earn a degree in science! You can pursue this fascinating field by way of an online education.

Archimedes' Law of Floatation Explained

Students with an affinity for Physics always have a quest for gaining knowledge about the mysteries of this world. Have you wondered how a vast ship sails calmly on the sea? Or, how a hot air balloon happens to go up in the air? Unfortunately, students cannot get all their questions answered in a classroom setting as there are several studentr seeking the attention of teachers. In such a case, you must consider hiring a private Physics tutor who will not only clear all your doubts but also explain the concepts further with the help of illustrations. In this article, we will discuss about the Archimedes law of floatation wherein the lies the answer to the above questions.

It is known that Archimedes was one of the best mathematicians of his time. He was also a physicist and an inventor. He was Greek by birth and there are several amazing inventions to his credit. He is known for the famous principle of floatation and the screw propeller. His works in the field of math includes discovering infinitesimals, formulas for measuring a circle, spheres, parabolas, cylinders and cones. The principle of floatation remains of his most recognized and popular inventions till date.

You will find it fascinating to know that Archimedes devised with most of his inventions to help his nation during the time of war. However, this principle was invented when a king asked him to verify the purity of a golden crown without harming it in any way. After days of pondering over it, the great scientist came up with an amazing solution and he took to the streets shouting 'eureka, eureka' in joy. The answer that he found was that he can find the density of the crown by measuring the volume of water that the crown displaced when immersed in a tub.

Thus, the Archimedes' law of floatation states that an object, whether wholly or partially submerged in liquid, experiences an upward thrust and the force is equal to the volume of the liquid displaced by the object. It is interesting to note that for any object that is completely submerged in liquid, the amount of fluid displaced is equal to its volume. And for an object that floats on a liquid surface, the volume of the displaced fluid is same as that of the object. This object experiences an upward force known as the buoyant force. If you wish to know more about the various inventions by Archimedes then hire a private physics tutor today.

Scientific Research Principles

Scientific research methods principally refer to a body of modus operandi used for investigating phenomena, thus acquiring new knowledge in the process. It also involves correcting and integrating previous known information to new heights.

Basis of a research

In order for a research to be considered as scientific, it must be based on certain accepted principles. Some of these are:

    The data collection must be through experimentation and observances.

    Information gathered must be measurable, observable and empirical.

    The evidence sought must be subject to precise principles of interpreting data.

    Steps followed are required to be repeatable in order to facilitate prediction of the upcoming results.

    The process must be out to prove a given hypothesis.

    Interpretation of results must never be biased.

    The evidence and results generated must be precisely documented for future usage by others. This involves writing of thesis and dissertations. The reason for this is to give future scientists an opportunity to have a look at your work, then attempt to improve or reproduce it and in so doing, verifying the results.

Conventional scheme of carrying out a research

At the end of a research, the scientist is projected to have formulated a hypothesis, analyzed and tested the findings, and lastly to have documented the final results. Nevertheless, the following points lead us to a pragmatic and widely accepted technique of carrying out a scientific research as shown below:

    Definition of the underlying question: The question is the subject of inquiry and is required to be well delineated in terms of the relevance, project cost, scope, time frame and availability of the needed resources.

    The information and resources required prior to the commencement of the project must be gathered in advance in order to avoid stalling the given project before its conclusion.

    Forming the hypothesis upon which the experimental processes involved in the research will be based on.

    The scientific data must be analyzed by the use appropriate techniques, for instance, the usage of tabulations, graphs and statistical software packages such as Statistical Package for Social Science (SPSS).

    Making the results accessible by publishing it in appropriate journals for future usage and reference.

    Lastly, retesting the results by other scientists to prove the authenticity of your work.

All in all, it is worthy to note that limitations when conducting a scientific research do exist and must be taken into considerations, and that it is virtually impossible to record everything that took place during the experimentation process comprehensively.

Tom Mc Carrick hosts Scientific Knowledge, a website where you can find out more on topics such as scientific research [] and much more.

Linear Motion System

Linear motion is the most basic of all motions. Objects that are not subjected to external forces will progress uniformly in a straight line permanently. Linear Motion is the movement along a line or length of area. Linear motion can be uniform at a constant speed, or non-uniform with fluctuating velocities (non-zero acceleration). The motion of an object along a line can be described by its position (x), which differs with the amount of time (t). Linear motion is sometimes called rectilinear motion.


A cam follower system is a system/mechanism that uses a cam and follower to create a specific motion. The cam is in most cases merely a flat piece of metal that has a shape or profile machined onto it. This cam is attached to a shaft which enables it to be turned by applying a turning action to the shaft. As the cam rotates it is the profile or shape of the cam that causes the follower to move in a specific way. The movement of the follower is then transferred to another mechanism or another part of the mechanism.


Actuators are devices that put the Linear motion system into automatic action. Actuators are used in a wide variety of applications, from industry machines producing products to computers starting up. Whichever type of actuator you need, there are several different types that can help you achieve putting things into motion. Shapes and styles distinguish actuators by use. There are three types of linear actuators, including basic, compact, and rodless cylinders. Both the basic and compact cylinders are best used when needed for a individual or dual action. Rodless cylinders are best used for long stroke applications in magnetic or mechanical systems. Another type of cylinder is the guided cylinder. This will provide a more stable precise movement that will eliminate bending.


Roller Slides, sometimes called crossed roller slides,are no motor linear slides that provide high precision linear movement for equipment powered by inertia or by hand. Roller slides are based on roller type bearings, which are frequently crossed to provide heavy load capabilities and more precise movement control. Roller Slides are mainly used in industries such as manufacturing, medical and telecommunications, and are versatile,with the ability to be adjusted to meet multiple applications which typically include clean room, vacuum environments, material handling and automated machinery. Roller slides work similar to ball bearing slides, except that the bearings are cylinder-shaped instead of ball shaped. The rollers cross each other at a 90 angle and move in between the four parallel rods that surround the rollers. The rollers are between "V" grooved bearing raceways, one being on the top and the other at the base. The travel ends when it meets the end cap. Typically, bases are constructed from aluminum and the rods and rollers are constructed from steel. Ball bearing slides are the most common type of linear slide. Ball bearing slides offer smooth precise movement along a guide rail, aided by ball bearings housed in the base,for increased reliability. Ball bearing slide applications normally include robotic assembly, cabinetry, high-end appliances and clean room settings, which primarily serve the manufacturing industry. For example, a widely used ball bearing slide in the furniture industry is a ball bearing drawer slide. Linear motion systems play an integral role in all of our lives and will continue to be important as we explore robotics and other technological advancement.

The Earth, the Sun, and the Stars

Our Solar System consists of the sun, planets, dwarf planets (plutoids), moons, an asteroid belt, comets, meteors and other objects. The Sun is the centre of our solar system and everything orbits around it.

The Earth is the third planet of our solar system- meaning it is the third from the Sun. Earth is the fifth largest of the eights planets in the Solar System, but the densest. It is the only astronomical body where life is known to exist.

The Earth's terrain varies from place to place. Roughly 71% is covered by water. The remaining 30% consists of mountains, deserts, plains, plateaus and other geomorphologies.

The Earth provides lots of natural resources, which unfortunately humans have been exploiting for centuries. Some of these are non-renewable resources which are difficult to replace in a short amount of time. Humans have access to useful biological products that are produced by the Earth's biosphere. These products include, food, wood, oxygen and the recycling of many organic wastes. The ecosystem that exists on land is dependent on topsoil and water. And the ecosystem that exists below water depends on the Earth's dissolved nutrients.

The Sun is the star at the centre of the Solar System. It is approximately 149.6 million kilometres away from the Earth. It takes about 8 minutes and 19 seconds for light to travel from the Sun to Earth. Almost all life on Earth is supported by the energy of this sunlight. This is achieved via photosynthesis, which is the chemical process of converting carbon dioxide into organic compounds using energy from sunlight. The sun also controls the Earth's climate and weather patterns.

A star is a luminous ball of plasma held together by gravity. The Sun is a star and it is the star nearest to Earth. By observing the spectrum, luminosity and motion through space of a star, astronomers can determine its age, mass and chemical composition.

For creation and sustainability to take place all parts of our ecosystem must work together. Trees play their part by producing oxygen and reducing carbon dioxide in the atmosphere. They also help to moderate temperatures on Earth. Trees serve many additional purposes such as building material from their wood, fruits from their vines, and their aesthetics for landscaping purposes.

To date humans have exploited quite a lot of the planet's natural resources. It is of course normal that we would need and use some of them, but it is our responsibility to be as prudent as we can. We need to keep our world prosperous and beautiful.

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