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Ley de Coulomb | Fórmula

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Culture & Science - Science
Tuesday, 19 March 2013 14:08

In Space Science we have already explained some of the principles of physics that have changed the course of history, see the Law of gravity , but the truth is that we can expand on this topic a lot more and speak now of the law is Coulomb and strongly related to the aforementioned universal gravitation. Let us now see what is, what is its formula as applied Coulomb's Law.

Article Index:

  1. What is the law of Coulomb
  2. Formulas Coulomb's Law

What is Coulomb's law:

  • We can define the Coulomb law as the law that determines the properties of electrostatic force arising from one or more electrical forces. It closely resembles the Law of Universal Gravitation.
  •   It was stated by Charles-Augustin de Coulomb in 1785, thanks to a torsion balance with which the experiments performed (thus measuring the force of attraction or repulsion suffering two electric charges).
  • As stated by Coulomb can say that: "The electric force exerted between two electrically charged bodies is directly proportional to the product of their charges and inversely proportional to the square of the distance that separated".

Formulas Coulomb's Law:

The equation of Coulomb's law is:

time F = frac {1} {4 pi epsilon} q_2 cdot frac {q_1} {d ^ 2} vec {u} _d = frac {1} {4 pi epsilon} cdot q_1 q_2 frac {(vec vec {d_2} {d_1})} {| vec {d} _2-time {d} _1 | ^ 3},!
  • F = force vector is suffering electrical loads. It can be attractive or repulsive, depending on the sign appears (depending on whether the positive or negative charges).
  • q = loads are subjected to the experiment.
  • Epsilon = permittivity.
  • ud = direction vector connecting the charges q1 and q2.
  • d = distance between charges.

The ratio 1/4 (pi) E is called Coulomb constant.

This law is also used for various loads (nth), the following equation:

time F = sum_i F_i vec = ^ N ^ N kappa sum_i q_i frac {q} {r_i ^ 2} time {u_r} _i,!

indicating the force caused by loads regarding a i, q.

  • As we can see by simple comparison, is very similar to the equation of universal gravitation, formulated by Isaac Newton
F = Gfrac {m_1 m_2} {r ^ 2},!

Application of Coulomb's law:

  • In case you have been very clear, or you need to give you an example of the application of Coulomb's law, perhaps one of the simplest is that of polythene bags.
  • Have you ever noticed that if you break a polythene plastic, which usually carry these appliances to protect them, possibly some piece will be attached to your clothes?.
  • Also costs quite suddenly remove it or not re-stick. This happens because we are "charged" by the friction of our clothes, air, etc.. these charges are opposite to the plastic and it is attracted to us and beats us.
  • Another example is to rub a rule against our clothes, then went through a sheet of paper and see how it stands up. Or put two balloons inflated, the rub and you can see the action of the Coulomb force.

Video on Coulomb's law:

Other items of interest in Espaciociencia:


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The 10 extinct animals that could come back to life

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Culture & Science - Science
Tuesday, 19 March 2013 14:08

I recently came the news that he could resurrect the mammoth thanks to advances in genetics , and also said he might even do it with Neanderthals . And is that both species have managed to sequence the genome altogether. Now they have gone further, and in an article in New Scientist named to the 10 extinct animals that could revive in a few years.

All that is needed is a well-preserved specimen which to extract a DNA sample, and thus obtain genetic information that could help complete the genome of these extinct animals.

So you just could do with some animals become extinct relatively recently, such as the dinosaurs is very difficult to be able to get enough genetic material to complete a genome. The DNA in the bones can not survive more than a million years.

So scientists are now sequencing the genomes of several extinct animals to someday bring them back to life. This should get some kind alive today that is similar, so that you can grow the embryo.

New Scientist has made the selection of the 10 animals that would be brought to life again. This has been based not only on the ability that can be made, but also with those animals charisma extinct.

Obviously to bring back to life animals that are extinct for a reason that has nothing to do with man, it would be a problem, because we should think about where they would live, etc.. But do not spoil the fun, and get on with the game, let's see the list:

1 - Homo neanderthalensis. Extinct about 30,000 years ago

Reconstrucción de muejer neandertal In the first place we have the Neanderthal undoubtedly one of the most charismatic extinct creatures, and the last human species among us modern humans. I have been working on finding the Neandertal Genome years, and has successfully completed a draft thereof. were believed to the end of 2009 will have the full genome.

2 - T igre Sabretooth ( Smilodon fatalis ) Extinct 11,000 years ago

There are many specimens of saber tooth tiger gives complete, and lions are similar enough to make surrogate.

3 - giant short-faced bear ( Arctodus simus ). Extinct 10,000 years ago

These huge bears on all fours had the height of a man is the giant version of the current bear. Frozen discovered many specimens as in the case of the mammoth .

4 - Tasmanian Tiger or Thylacine ( Thylacinus cynocephalus ). Extinct in 1936.

The last of its kind died in Hobart Zoo in 1936, so they have enough uncontaminated tissues to get a good quality DNA.

5 - Gliptodonte ( Glyptodon clavipes ). Extinct for 10,000 years.

This armadillo supergiant would be very interesting to see him alive, if their bones are already huge. (The list continues after the image)

Gliptodonte / Wikipedia

6 - The Dodo ( Raphus cucullatus ). Extinct in 1690

This bird so famous and so interesting of the islands Mauritius has a well-preserved specimen, and in 2002 geneticists at Oxford University and is working with its genome.

rinoceronte lanudo 7 - woolly rhinoceros ( Coelodonta antiquitatis ). Extinct about 10,000 years ago.

Like the mammoth, the giant hairy rhinoceros that was less than two meters high has been preserved in many specimens frozen.

8 - Megatherium Giant Sloth ( Megatherium ). Extinct 8000 years ago

When stood on his two feet could reach up to 6 meters high. There are many remains of which can get DNA, and it has been so long since extinct.

9 - giant deer or Irish elk ( Megaloceros giganteus ). Extinct 7700 years ago.

This giant deer could reach two meters in height, with antlers that could measure up to 4 meters wide. There are sufficient to collect DNA specimens and is very similar to the current deer, only giant.

10 - The Moa ( Dinornithidae ). Extinct by 1500.

This bird similar to an ostrich could reach up to three meters high, and living in New Zealand, there are enough bones and even eggs, from which genetic material obtained.

Ciervo gigante


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Torricelli: the horror of the vacuum and air pressure

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Tuesday, 19 March 2013 14:08

During the seventeenth century, the natural sciences have benefited greatly from the development of experimental methods compared to pure reason.

The rapid evolution of astronomy and mechanics, also joined him progress in studies of the atmosphere and air pressure.

image Evangelista Torricelli (1608 - 1647)

In the physics of Aristotle, there was a theory he formulated a horror, or rejection, that nature had for the vacuum: the "horror vacui".

Everything seemed to demonstrate that easily observable nature "refused" to tolerate the absence of air, that is, that nature abhors a vacuum.

Today we know that such phenomena are the effect of the pressure of the surrounding air, the air's natural tendency to expand and fill the containers at your fingertips.

image

Galileo knew that air had weight, but there was no relationship between this data set and the fact, already known at that time that a suction pump can not suck water when it is located at a depth greater than 10 meters.

Today we know that is the air pressure that leads to the water at that level in an empty tube of air.

It was the countryman and disciple of Galileo, Evangelista Torricelli (1608 - 1647), who found that air pressure represented.

In the course of testing, Torricelli mercury column used instead of water. The mercury is 14 times heavier than water.

Mercury filled glass tube one meter long, closed at one end, covered with his finger and put the other end of the glass tube in a vessel containing mercury.

image

By separating your finger tube, observed that some of the content is spread in the container, but the tube was still a column of mercury of about 75 cm. tall.

Torricelli proved so when the mercury fell, leaving a gap at the top. And she assumed, quite rightly, that something had to be atmospheric pressure.

image

In addition, he noted that the height of the mercury column varied slightly from one day to another, and this phenomenon is called atmospheric pressure variations.

In other countries also conducted studies on same vacuum and air pressure. In France, made ​​Blaise Pascal , in England, Robert Boyle , and in Germany , Otto von Guericke. The latter also demonstrated that light, and not just the sound, could propagate in a vacuum.

Sources: Editorial Sunya / Britannica / Focus, Technique and Material, Editorial Argos, Barcelona / Images: Ebrisa


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Are the dinosaurs were nocturnal hunters?

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Culture & Science - Science
Tuesday, 19 March 2013 14:08

Contrary to popular thought, some dinosaurs were not asleep when the sun. According to new research, many animals stayed awake at night to hunt prey.

image

This discovery, based on fossil evidence eyes the remains of dinosaurs , contradicts the conventional information that claimed that early mammals were nocturnal, or active at night because they were dinosaurs during the day.

But to respond if there are chances that dinosaurs were nocturnal hunters is a very difficult task because, as we know, only remain some fossilized bones.

The group of scientists set about this task began by analyzing the size of the ocular cavities, and the dimensions of the scleral ring, a region of the bones surrounding the iris of the eye in birds, lizards, and dinosaurs (humans and other mammals not possess).

Scleral ring The study could shed some light on the subject, because the nocturnal animals need to capture the maximum amount of light possible, and this requires greater openness within the scleral ring.

By contrast, diurnal animals have small eye openings, allowing them to save energy and not have to get his pupils constantly in daylight, and it allows them to see clearer and sharper images at long range during the day.

image Andrewsi Protoceratops, active herbivore night and day

In the fossils, the researchers examined the proportions of certain features of the eye to determine the habits of the species analyzed. They then compared the information obtained from the data of species today.

Around about 33 species of dinosaurs that lived during the Mesozoic period (between 250 and 65 million years ago) were similar in their characteristics to the lifestyle of modern animals.

It was found that 8 species of flying dinosaurs, three species of pterosaurs would be awake during the day, while five species were nocturnal or active during periods of the night. Two of these five species rather their behavior asemejarían of nocturnal seabirds today.

image Fossil belonging to a Velociraptor, nocturnal activity

Most herbivorous dinosaurs stayed awake periodically. The enormous size of these animals mean that spent much time feeding and grazing during the day and night. In addition, these animals were prone to heat stroke, so trying to avoid activity during the hottest times of the day, exchanging his move in the evening hours, according to the study.

Finally, predators, both dinosaurs like these, get always an advantage when hunting at night, and all analyzed predatory dinosaurs were nocturnal or active at night regularly.

In conclusion, the result of the research indicates that dinosaurs and early mammals did not separate the day from the night in the course of their activities, as they do most mammals.

Source: Science


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