Earth Gravity – Distinguishing the Forest and Trees

Education, Physics
There's no point attempting to explain the precise nature of gravity here. Most of us are aware it is Earth gravity that enables us to remain standing on the planet. Gravitational force operates on all matter.¹ Is Matter the Same as Weight? No, the two are not the same. To illustrate, say a man is seated at the doctor's office and he is invited back. He is requested to stand on a scale. It says he weighs 210 lbs. We write w = 210 lbs. Now say that man is an astronaut. Ah! Next week he is deep in space. If he removes his restraints, he begins to float. He is weightless!² That is, w = 0 lbs. Yet his mass remains the same. That is, m ≠ 0. Weight…
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Static Friction and Kinetic Friction AKA Sliding Friction

Education, Physics
You return home. You find that while you were gone, the UPS man dropped off a large cardboard box in front of your garage. The box is made of very thick cardboard. Clouds are rolling in. You need to put the box in the garage. But it's just you and the box is super-heavy. You have no alternative but to push it in. You Take Note You've had your coffee today, so you're on top of your game. Your mind is sharp as it will ever get. You position your hands and shove the box with everything you've got. You give it your best! Curiously once it starts, it isn't that hard to move, as long as you keep moving. You realize with that Sherlock Holmes brain of your that…
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Fission Energy Vs. Total Energy of Uranium-235

Nature, Physics
The fission of one atom of uranium-235 releases 3.24 × 10-11 Joules of energy. One mole of atoms (235 grams) produces 6.022 x 1023 times that amount of energy.¹ How much energy is that? Energy From Splitting One Mole Uranium-235 Atoms We calculate, Eone mole 235U = 3.24 x 10-11 x 6.022 x 1023 = 1.95 x 1013 Joules or 19,500,000,000,000 Joules. This is a tremendous amount of energy. It is the energy of each mole of uranium found in an atomic bomb! It is millions of times more energy than any chemical reaction. But is this the ultimate energy matter can produce? By no means! Total Energy in One U-235 Atom When an atom of uranium is split, it does not entirely disappear. Rather, fragments are produced – atoms…
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What is Hexagonal Boron Nitride? Why Is It So Interesting?

Electrical, Physics
Boron, like many other elements, forms nitrides. These nitrides can assume a variety of crystalline structures. One of those varieties consists of atoms in hexagonal array, layered in sheets. It is hexagonal boron nitride, or h-BN. A sheet of h-BN outwardly resembles a sheet of graphene. For this reason, some refer to it as graphitic boron nitride. We shall see that, despite a considerable similarity in appearance on papers, there are major differences between graphene and h-BN as well. Very significant differences. Graphene Vs. Hexagonal Boron Nitride Atomic spacing within a single layer of hexagonal boron nitride varies slightly from that of a sheet of graphene. As a result, graphene is black, while h-BN is white! [caption id="attachment_24819" align="alignleft" width="340"] Powdered h-BN - Image Indiamart[/caption] Graphene's C–C bonds are non-polar…
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Electronegativity of Atoms: What are Determining Factors

Chemistry, Physics
[caption id="attachment_24637" align="alignright" width="480"] 5d molecular orbital - Image Dhatfield[/caption] When two different types of atom are bonded together, they do not share their bond electrons equally. This is because each type of atom possesses its own charge environment, which results in an atom’s electronegativity. Electronegativity is the measure of an atom’s ability to attract additional electron density to itself. For example, Sodium seeks to give an electron to become a positive ion, Na+. It has a very low electronegativity. Iodine wants to gain an electron to become a negative ion, I-. It has a relatively high electronegativity. Charge Environment Atoms vary in electronegativity, and bonds vary according to constituent atom electronegativities. The electronegativity of an atom depends upon its charge environment. That environment depends primarily on three things... Distance…
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Differences Between Bound and Unbound Electrons

Chemistry, Physics
Atoms are constructed of a central nucleus, containing positively-charged protons and uncharged neutrons, plus orbiting, negatively-charged electrons, in number equal to the number of protons. Although an electron carries a charge equivalent (though of opposite polarity) to that of a proton, its mass is a mere 1/1836th that of a proton. Some mistakenly think the electron isn’t a particle at all, but a cloud. This inaccurate notion doubtless arises from the cloud-like appearance of the probability distribution curve of an electron in its orbit. At any rate, an electron generally exhibits particle-like properties, and is best mentally envisioned as a particle. How the particle we call an electron behaves depends upon the condition in which we find it. There are important differences between bound and unbound electrons. [sc name="MidArticleAdsense"] The…
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Diatomic Molecules: Degrees of Freedom and Equipartition of Energy

Chemistry, Physics
[caption id="attachment_24378" align="alignright" width="480"] A useful, but rough working model[/caption] Diatomic molecules have three translational degrees of freedom – but they have rotational and vibrational varieties as well. How do all these degrees of freedom relate to the distribution of molecular energy? To Begin With The location of any particle lies within three-dimensional space. The direction in which a particle moves is described by the three variables, usually written X, Y, and Z. As Ken Koehler of the University of Cincinnati informs us, atoms may be viewed as single points without size – so there are only three translational degrees of freedom for a given atom. Degree of Freedom of Diatomic Molecules Although it’s tempting to assume only three degrees of freedom exist for all “particles,” such is not the…
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Cooling Atoms to Millionths of 1 Degree by Laser?

Physics, Technology
[caption id="attachment_24362" align="alignright" width="480"] Laser trapped erbium atoms. Image by NIST[/caption] Laser cooling refers to a variety of techniques. The most common method is Doppler laser cooling. But cooling atoms by laser? Although the math and physics are challenging, we can understand the idea and basic mechanism more easily when we introduce three basic concepts first: quantum absorption of energy, the Doppler effect, and how atomic motion correlates with temperature. The Absorption of Energy "Quanta" It is at the very heart of the quantum theory that an electron bound in an atom cannot absorb just any amount of energy it encounters. In the free state, it can, but as soon as the electron is restrained as part of a new structure in an orbital, only certain discrete amounts of energy…
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Muonium: An Atom Similar to Hydrogen, Only No Protons!

Chemistry, Physics
[caption id="attachment_23970" align="alignright" width="480"] No proton![/caption] You heard correctly! From cosmic ray bombardments and particle accelerator experiments comes “muonium,” an other-worldly form of atom that, to a degree, resembles hydrogen. This atom is fascinating research scientists, along with another oddball, positronium. Muonium: An Exotic Element… Sort Of There are some 90 naturally-occurring elements on Earth. There are more than a dozen other artificial elements, as well. Muonium is artificial, but not in the usual sense of the term. All of the more than one-hundred elements found in the periodic table consist of atoms made up of electrons traveling in orbitals about respective nuclei containing one or more protons and neutrons. Though muonium does have an electron orbiting a nucleus, it possesses no proton or neutron. Instead, muonium’s nucleus consists of…
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Beer Bottle Condensation: What Forces Produce Droplets?

philosophy, Physics
Dan asked us¹... "My question concerns condensation. What dictates how droplets form, then combine with each other? When you blow warm breath onto a cool surface, at first nothing appears to happen. Keep it up and droplets appear. These small droplets merge into bigger droplets. What physical laws dictate how this occurs? Also, what role does gravity play on vertical surfaces such as a chilled bottle of beer, producing tiny rivulets of moisture running down the sides?" Initial Commentary The answer, which follows, although it has some basis in well-known physical principles, depends in part upon observation, mental visualization, and (finally) blatant speculation. This is an interesting procedure, since so many of life’s mundane occurrences are in reality quite fascinating when closely examined. Initial Condensation We breathe in and breathe…
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