Physics Weekly Newsletter - Monday, June 30, 2014

Top new questions this week: Can I compute the mass of a coin based on the sound of its fall? Other day, I bumped my bookshelf and a coin fell down. This gave me an idea. Is it possible to compute the mass of a coin, based on the sound emitted when it falls? I think that there should be a … waves acoustics everyday-life home-experiment   asked by Vinicius L. Beserra 104 votes answered by alemi 205 votes Does Earth really have two high-tide bulges on opposite sides? The bit that makes sense – tidal forces My physics teacher explained that most tidal effect is caused by the moon rotating around the Earth, and some also by the Sun. They said that in the Earth and … newtonian-gravity everyday-life education tidal-effect   asked by Benjohn 70 votes answered by David Hammen 85 votes Why does our voice sound different on inhaling helium? This question (and answer) is an attempt to clear the air on what appears to be a very simple issue, with conflicting or unclear explanations on the internet. Arguments, negations, etc are invited. … acoustics resonance   asked by Dev Kanchen 34 votes answered by Dev Kanchen 35 votes Are we slightly lighter during the day and slightly heavier at night, owing to the force of the Sun's gravity? Using $g = \frac{Gm}{r^2}$, the force on a point mass located at 1 AU from the Sun ($m = 2 \cdot 10^{30} \text{ kg}$) is about ~0.006 N/kg. Does that mean that, e.g., a 70 kg person is ~42g lighter … homework newtonian-gravity tidal-effect   asked by John Feminella 32 votes answered by John Rennie 26 votes What does a wing do that an engine can't? This isn't a question of how a wing works -- vortex flow, Bernoulli's principle, all of that jazz. Instead, it's a question of why we need a wing at all. A wing produces lift, but why is that … aerodynamics aircraft lift   asked by yshavit 22 votes answered by Jani Kovacs 5 votes How badly could someone be injured by concentrated sunlight? Recently-ish, I stumbled across an interesting short story (by way of Science Fiction & Fantasy Stack Exchange) where a soccer referee is apparently incinerated by concentrated sunlight. Where … thermodynamics energy everyday-life sun thermal-radiation   asked by michaelb958 10 votes answered by Chris 12 votes Interpretations of quantum mechanics It is well known that there are many interpretations of quantum mechanics. I'm wondering if there is a specific reason why the Copenhagen interpretation is the most popular. Why is it that the … quantum-mechanics quantum-interpretations   asked by user119264 10 votes answered by alemi 9 votes Greatest hits from previous weeks: What software programs are used to draw physics diagrams, and what are their relative merits? Undoubtedly, people use a variety of programs to draw diagrams for physics, but I am not familiar with many of them. I usually hand-draw things in GIMP which is powerful in some regards, but it is … soft-question software   asked by Mark Eichenlaub 91 votes answered by nibot 46 votes How does water evaporate if it doesn't boil? When the sun is out after a rain, I can see what appears to be steam rising off a wooden bridge nearby. I'm pretty sure this is water turning into a gas. However, I thought water had to reach 100 … water temperature evaporation   asked by Crummy 18 votes answered by Peter 15 votes Can you answer these? Why and how almost periodic series constitute the algebra of observable of integrable systems? In the introduction of his book Noncommutative Geometry, p. 42, Connes explains that when a classical dynamical system has enough constants of motions, the motion of the system is almost periodic, … classical-mechanics resource-recommendations integrable-systems   asked by Georg Sievelson 2 votes Problem with shell model and magnetic moment of Lithium-6 I have a problem with the calculus of magnetic moment of Li-6. The configuration of protons is $1p_{3/2}$, and the neutrons' one is the same. I have to add the magnetic moment of uncoupled proton … homework nuclear-physics   asked by sunrise 4 votes Why does sand stick to my shoes? Well, that's easy: the sand is wet, and my shoes are wet, and hydrogen bonding adheres the wet sand to my wet feet and to my shoes. But then I walk home, and my shoes dry, and the sand on them dries, … everyday-life bonding   asked by MJD 9 votes

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