Mike Dunlavey

4,239 reputation

714

bio	website	en.wikipedia.org/wiki/…
	location	United States
	age	68
visits	member for	1 year, 8 months
	seen	3 hours ago
stats	profile views	417

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)

	4,239 reputation	bio	website	en.wikipedia.org/wiki/…	visits	member for	1 year, 8 months
714 badges		location	United States		seen	3 hours ago

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Mar 20	comment	Surviving Free Fall with the Help of Mr. Bernoulli @John: You're right, but it's not so much about gaining speed as about reducing the angle of attack.
Mar 19	comment	Speed of the Moon Your profile says you're a postdoc in physics, so this question seems a bit strange.
Mar 18	comment	Explanation for different boiling points of water on different altitudes + It works the other way too. Underwater, at a depth of 1km, the water can get up to around 300C without boiling, as shown in this article.
Mar 16	comment	effect of internal forces to a glider's descent Yeah, you're basically right, I think, but don't think of the glider as making sudden changes in descent angle. Rather think of it as experiencing temporary changes in vertical acceleration, giving it short smooth curves down or up, such that the center of mass (man & glider) follows a straight line.
Mar 14	comment	effect of internal force to a glider's descent David's right, but I would suggest you make an analogy to someone jumping on a trampoline, while the trampoline is supported on a scale.
Mar 11	comment	Experiment to measure initial speed of high speed tennis ball? Nice. This is like the Charpy test I learned in undergrad materials science.
Mar 11	comment	Experiment to measure initial speed of high speed tennis ball? Fire it horizontally, and measure how far it goes before it hits the ground. You can calculate (or measure) how long it would take if simply dropped. That's how long it takes to go that distance. This only works if there's no spin involved. Add a fudge factor for air resistance.
Mar 6	comment	Water, how do you make ripples Shine a light on the water in the bowl and watch the reflection. It should just look like a simple mirror. Then drop in your pebble. The reflection will be all messed up for a little while. That's your ripples.
Mar 6	comment	What is the optimal weight for a golf ball? It isn't force that you're hitting it with. You have a collision between elastic objects, the ball and the driver, so think of it in terms of the momentum transferred from the driver to the ball.
Mar 6	comment	Flow in parallel paths after pressure regulator @wupdiwup: There's only one thing a valve sees - the pressure drop across it. The only way flow through valves B and C can reduce the flow through A is by reducing the pressure that A sees. If the pressure regulator is doing its job, that cannot happen. You have to make sure the pressure regulator can keep up the pressure even with all three valves open.
Mar 5	comment	Flow in parallel paths after pressure regulator + As long as the pressure regulator does its job and maintains a constant pressure going into each valve, that's all the valve will see.
Mar 5	comment	Understanding Quantum Physics @EmilioPisanty: Thanks. Good edit. One of the best hours I've spent. I love his salt-of-the-earth presentation and Brooklyn accent.
Mar 5	comment	Understanding Quantum Physics @Kitchi: I put it above. Actually wizzup found it at youtube.com/watch?v=hUJfjRoxCbk
Feb 27	comment	Aircraft nose-up glide @Jodes: No. That would depend on how the wings are mounted, what the glide ratio is, and what the speed is. For the C172, the glide ratio is about 9:1, so the descent angle would be about 6 degrees down. The angle of attack would be about 10-15 degrees up, totalling about 4-9 degrees above horizontal. I'm not sure what angle the wings are mounted at. It also depends on the pilot's height and how high the seat is adjusted w.r.t. the cowling. There's no natural line indicating "true horizontal" on an airplane. It's all relative. At high speed it feels like falling out the front.
Feb 24	comment	When did Voyager-1 achieve Solar System escape velocity? @Chris: The diagram in my answer says Voyager 2 exceeded solar escape velocity in its encounter with Jupiter, and then more with Saturn. I can't find a similar diagram for Voyager 1, but it must have been similar. According to the list of escape velocities, at Earth, it takes 11.2 km/s to escape Earth, but 42.1 km/s to escape the sun. That's like 14 times as much energy. That's how much harder it would be without the slingshot effect.
Feb 24	comment	Measuring acceleration of a bus using water between two sheets of glass + nice answer. There's a simple way to measure it. Measure the height $h$ and base $b$ of the triangle. Then the acceleration of the bus is $g$ times $h/b$ (assuming driving on a level street).
Feb 21	comment	Why does string not wick down? @Adam: Also, where the string bends over the edge of the cup, I would assume the string is somewhat laterally compressed at that point, squeezing shut the voids that the capillary flow goes through.
Feb 21	comment	Needed Energy For Lifting 200 kg weight Energy is force times distance, that is, weight times height. Power is energy per unit time, so if you lift it slow, it doesn't take much power. If you lift it fast, it takes a lot of power. After you run the numbers, it's just a matter of converting units.
Feb 21	comment	At an acceleration of 2ft/s^2, how fast could I reach 9.8MPH? Convert miles per hour to feet per second, and go from there. I'm trying not to just give you the answer.
Feb 20	comment	Was the 2013 meteor over Russia stronger than an atomic bomb? You're right. I was referring to sentiments that look down on "left wing" or "anti war". In the former Czechoslovakia we (USA) were on the right side. In Vietnam, we were on the wrong side. We got there largely because of a perceived need to show the USSR & China & our own voters how tough we were. Nixon & Kissinger artificially prolonged the war for political reasons, at terrible cost, especially to the people of Vietnam, Cambodia, and Laos. So all I'm trying to say is - if somebody is in a different "camp", respect it.