Mike Dunlavey

4,199 reputation

714

bio	website	en.wikipedia.org/wiki/…
	location	United States
	age	68
visits	member for	1 year, 8 months
	seen	12 hours ago
stats	profile views	416

BS Mechanical Engr.
PhD CS(AI)
CS Prof (4yr)
Numerous consulting jobs.
15 yr at http://www.pharsight.com
Published book on CS & several articles
4 kids, 2 grand
Pilot(student)

	4,199 reputation	bio	website	en.wikipedia.org/wiki/…	visits	member for	1 year, 8 months
714 badges		location	United States		seen	12 hours ago

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Feb 16	comment	Was the 2013 meteor over Russia stronger than an atomic bomb? + I'm not sure you made it clear that, neglecting radioactive fallout, the initial damage is caused by 1) radiative heat and 2) acoustic blast wave/sonic boom. In this case, since the event was about 19km above the ground, the heat was not too bad at the surface, especially considering slant range. The acoustic wave was also at a distance, but it still pulverized a lot of windows (2 minutes later), which injured a lot of people who were looking out those windows. Many people injured in Hiroshima/Nagasaki were hurt the same way.
Feb 11	comment	Staying in orbit - but doesn't any perturbation start a positive feedback? I was going to answer that orbits are ellipses where the sum of potential and kinetic energy is constant, so all your perturbation does is set it on a different ellipse. But that's basically what John Rennie said first.
Feb 11	comment	Staying in orbit - but doesn't any perturbation start a positive feedback? + Nice. This is close to the answer I was going to give.
Feb 8	comment	Weightlessness on Earth My son once asked me if you had to go to space to be weightless. I had my car keys in my hand and told him to watch them while I gently lofted them up, holding my hand about an inch below them, and catching them on the way down. See? I said. They were weightless. It's a cheaper demo than a ride in the Vomit Comet.
Feb 7	comment	Do I need to have an airtight container to siphon boiling water? As Raindrop said, first make it work with room-temperature water. Then with hotter water. Then with boiling water. The only thing tricky is how to get it started. To do that, you could use flexible tubing immersed in the water. Fill the tube with water, and then pinch shut one end, lift that end out of the water and stick it in the other pot, making sure the pinched end is lower than the original water surface. Then un-pinch it, and it should run.
Feb 6	comment	When driving uphill why can't I reach a velocity that I would have been able to maintain if I started with it? @Joe: Every engine has a performance curve of torque vs. RPM and power vs. RPM. Both curves have peaks, after which they fall off with increasing RPM. Depending on the gear you're in, it's possible to have a stable speed (on the slope) which you might not be able to get to from a slower speed without being able to use just the right gear ratio. That's why trucks have transmissions with so many ratios. Otherwise, they could get into a climb where the lower gear would over-rev, and the next higher gear would lug.
Feb 4	comment	Predict final temperature by taking temperature samples? + I came up with that method in the context of pharmaco-kinetics, and a friend said it had a name: Aitken Acceleration.
Jan 29	comment	The Z-Torque: how can it be shown intuitively that it does not work? My way of saying this is: Pretend you're a foot. Something stiff is constraining you to move in a circle about a center. If that something is straight or crooked you can't even see, because you're a foot.
Jan 26	comment	Quantum Computing Power Advantages @Juan: I agree. I was just trying to keep the answer short for an unsophisticated OP. I've experimented with a simulation of Grover's algorithm.
Jan 23	comment	Potential energy of a spring You should know better :) The energy is the integral of $Fdx$. Your gravitational example is only good at short range where you can assume $mg$ is constant. Over a longer range it is not constant, and spring force is not constant either.
Jan 22	comment	Transformators (primary and secondary windings) @Ylyk: Well, it's got to matter, because a factor of 1.4 in voltage is a factor of 2 in power, so you could burn things out if you misunderstood it.
Jan 22	comment	Transformators (primary and secondary windings) @Ylyk: You'd have to read the placard on the transformer. I think it's typical to be rated in terms of peak voltage, not rms.
Jan 22	comment	Why aren't gas planets and stars fuzzy? Since you're asking this to make people think, and I bet you could make a good answer, why don't you answer it yourself?
Jan 18	comment	How much effect does the Bernoulli effect have on lift? @Alyosha: Pretend you're a wing. You can only be lifting if the pressure underneath exceeds the pressure above. Then pretend you're a slug of air. This wing comes along, cuts you in half, then pulls/pushes you downward. Same thing.
Jan 18	comment	How much effect does the Bernoulli effect have on lift? @Marty: I just think John S. Denker's book is terrific. He's a flight instructor, world-class physicist, and great teacher. I can read his stuff over and over and keep getting more out of it.
Jan 18	comment	How much effect does the Bernoulli effect have on lift? @Alyosha: There really isn't a larger thing. If you really want basics, you can go back to Newton's laws. Bernoulli's principle is just a consequence of Newton's laws.
Jan 18	comment	How much effect does the Bernoulli effect have on lift? @Marty: Yes. There is more than one way to analyze it.
Jan 18	comment	Why are magnetic lines of force invisible? You can only see things if they generate, absorb, reflect, or refract light. BTW, you can see magnetic fields by using iron filings.
Jan 16	comment	Turboshaft Turbine Mathematical Model Good question. I'm sure it depends on the resistive and inertial load of the driven turbine.
Jan 14	comment	thought experiment involving water pressure + @Hapjake: Amount (volume) of water can be divided, but not pressure. Pressure depends purely on the height of water above the point at which the pressure is measured. An easy way to think of it is, suppose you have a tube with cross section 1 square cm, and you insert it into the water. Then the pressure at the bottom is just the weight of the water above the bottom (in the tube).