## Trick Question About a Balloon

Do your ears perk up when you are asked a "trick question"? Well I have one about a balloon for you. Which weighs more, an empty balloon or a helium-filled balloon? When I first thought of this one, it took me a minute to realize the answer myself. Stop for a moment. Close your eyes and think this through. Have you arrived at an answer? Are you sure you're right? We'll provide some specifics in giving our answer - an example. Providing Specifics A typical empty balloon weighs between 1 and 5 grams. Let's say it is 3 grams. You could easily fit it within a 1"x1"x1" cubic block. OK. What size will our balloon be after it becomes a helium-filled balloon? Let's pick a believable size, say 9" around.…

## How Much Does a Fly Hitting a Train Slow It Down?

[caption id="attachment_27068" align="alignright" width="480"] The Scenario: a fly hitting a train.[/caption]Say you have a train, a locomotive traveling along a straight railroad track. The atmosphere is absolutely free of every conceivable impediment except for one lone housefly. Unfortunately (for the fly), it and the train collide head-on. You have a fly hitting a train. Clearly, the fly will turn into a smear. How much does that fly slow the train down that it has hit? The train will suffer no apparent change in speed, yet it does slow down, even if there is no obvious change. How much does it slow down? Fly Hitting a Train: Specific Numbers We will attempt to use realistic numbers. We choose the following: Locomotive: 4,000 tons [a light train] Fly: 14 milligrams Locomotive Speed:…

## In Simple Terms: The Heisenberg Uncertainty Principle

[caption id="attachment_26306" align="alignright" width="480"] L to R: Niels Bohr, Werner Heisenberg, Wolfgang Pauli[/caption]Werner Heisenberg (1901-1976) was yet another bright German physicist. He was a "founder" of quantum mechanics, the physics of the subatomic. As with astrophysics, behavior at this level appears to vary from the physics of the everyday world. A Brief Description The velocity of an auto of mass m can be measured accurately. If its velocity remains constant, its location over time is predictable. This is the norm according to ordinary human experience. Yet, at submicroscopic levels, physicists experienced something different. For certain measurements, various pairs of variables could not both be accurately known simultaneously. Simultaneous measurement is only precise to a point. These pairs of variables are termed conjugate variables. The Standard Example The simplest example is…

## Ozone – The Other Oxygen: A Brief Discussion

Ozone (O3), a triatomic form of the ordinarily diatomic oxygen (O2), is a curious species. We will discuss some of ozone's curious physical properties. We will not include information related to health or the environment. Molecular Bonding Just as it takes two points to determine a straight line, diatomic oxygen is also linear. It's bond length is 1.208 Å (equal to 120.8 pm). Ozone is not linear; it is bent at an angle of 116.8o, which is greater than the measure of the angle for a water molecule, 104.5o. Comparing Boiling Points The third oxygen atom plus the relatively large angle suggests ozone should boil at a higher temperature than oxygen. In fact, this is the case. This is because the bent ozone molecules, as seen in the illustration, produces…

## Earth Gravity – Distinguishing the Forest and Trees

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…

## Static Friction and Kinetic Friction AKA Sliding Friction

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…

## Fission Energy Vs. Total Energy of Uranium-235

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…

## What is Hexagonal Boron Nitride? Why Is It So Interesting?

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…

## Electronegativity of Atoms: What are Determining Factors

[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…

## Differences Between Bound and Unbound Electrons

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. The Free-Moving, Unbound…