8,810 reputation
1730
bio website en.wikipedia.org/wiki/…
location United States
age 71
visits member for 3 years, 11 months
seen yesterday

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)

P.S. The picture is a Beta-prime distribution. It shows the program speedup factors you can get if you see a problem twice in 2, 3, 4, and 5 samples.


Jul
17
comment What is the speed of electrical current in salt water?
@udiboy: Aren't we talking about two different things? Take the analogy of a water hose of some length, full of water, with a valve at the far end. If the valve is suddenly turned on, water starts coming out of the near end almost immediately, but the actual velocity of water molecules need not be very fast.
Jul
17
comment A book sits on a table. What is the net force of air pressure?
@metacompactness: touche'. I ignored the weight of the objects, and the weight of the displaced air.
Jul
16
comment What is the speed of electrical current in salt water?
I think you're trying to ask this: If there is a resistive mass of saline, with two widely-separated electrodes in it initially at ground potential, and one electrode is subject to a voltage step at time 0, how much later will the voltage be felt at the other electrode? If that's your question, I would vote for John's answer.
Jul
16
comment Local real-time lightning tracker site?
It's a good question. Aircraft can carry storm-scopes, and possibly there is such a thing at local weather broadcasters. Also look here.
Jul
15
comment How to derive a physical model of temperature above the earth surface?
@Jim is right. You need to consider solar heating or/and radiational cooling, local wind, vertical mixing. With solar heating, you get localized "mushroom cloud" updrafts. There is something called the "dry adiabatic" lapse rate, where simple vertical motion results in expansion/compression, resulting in temperature change. Add to that the role of moisture, where evaporation absorbs heat (thus cooling) and condensation releases heat (thus heating), plus the fact that humid air is less dense than dry air, and it becomes a lesson in meteorology.
Jul
12
comment Where does the light go when I turn off the light switch?
I love the questions that children ask. If you're spraying water with a hose, where does the water go when you turn it off? If you're pitching baseballs, where do they go when you stop?
Jul
11
comment why does gravitational force bring the clouds down?
+ Minor note about the flat bases: You don't have a layer of warm and a layer of cold. You have a more-or-less linear drop in temperature with altitude (the lapse rate), caused by various things like 1) rising air expands, thus cools, and vice-versa, 2) surface heated by sun, etc. If the rate is too steep the air is unstable & you get localized updrafts and clouds like above. If less, you get stratified clouds. If negative, you have a temp inversion, like in Los Angeles smog.
Jul
9
comment Extreme heating by Sun on Earth- Can eggs be fried?
@udiboy: Should work, except if you pump all the air out, the egg would boil. (That would be a mess.) How long would it take? I don't know. BTW, it would probably be a good idea to shield it from the sky around the sun, because that's colder, and could lose heat through radiation. (For the same reason, the chamber should be insulated so it can also come up to temp.)
Jul
6
comment Are Electromagnetic Waves The Only Means of Transmitting Information?
+ You're right, but even the physical means are based on EMF, because when one piece of physical matter impinges on another, it is the electromagnetic interactions that prevent them from moving through each other.
Jun
27
comment why can't you use your cellphone on an airplane?
@David: The thing is, the answer to the question is only marginally about physics or electronics or aeronautics. It's really about risk. There are plenty of rules in aviation that sound like superstition until you realize what the stakes are.
Jun
26
comment Why is the Pegasus launched from a subsonic airplane?
Another reason for using a carrier aircraft is to get above most of the thick air.
Jun
23
comment What does a curved natural log graph suggest?
@NeuroFuzzy is right. If flow rate is proportional to pressure-at-hole (head) then you should see exponential decay. However, that is only true in the viscous limit. For inviscid flow, flow rate is proportional to square-root of pressure, because of energy balance.
Jun
22
comment Does my model aircraft propeller beat the sound barrier?
+ WW2 fighter aircraft also had reduction gearing. Like the F4U Corsair had 2:1 reduction because the prop had a 13' diameter.
Jun
21
comment In a turning plane, will the vector of combined centrifugal plus gravity force experienced by passengers be perpendicular to the floor?
It's no different from turning a bicycle, motorcycle, high-speed boat, or any vehicle that banks in turns. The only difference in a plane is that there is a rudder, which, if used, can create a relatively small sideways force by putting the plane somewhat crossways to the wind.
Jun
21
comment How much effect does the Bernoulli effect have on lift?
++ Your PDF is a much better explanation than your answer here. When you denigrate the Bernoulli Effect, you're referring to the version commonly and incorrectly taught. With some editing, this could be a nice answer.
Jun
21
comment How much effect does the Bernoulli effect have on lift?
Yeah, that video is pretty good. The only question is it refers to the Coanda effect above the wing. Denker explains why that's not right.
Jun
21
comment why can't you use your cellphone on an airplane?
From a pilot's perspective, what matters are the odds. If there is the slightest chance of a problem, and the stakes are high, it's probably not worth taking that chance just for some people's convenience. The accidents that happen are ones thought to be unlikely.
Jun
11
comment Calculating rotor torque out of mass center
I don't understand your use of the word "fit", as in "after fitting this engine out of mass center". Any such question can be answered by considering a propeller blade to be a rotary wing.
Jun
5
comment Static as opposed to Kinetic Friction in Rolling Motion
Since you're talking about rolling motion, it might be useful to understand how gears work.
Jun
4
comment What is the Coandă effect? How is it defined, and what causes it?
Try this terrific site. It discusses the Coandă effect and how it is different from the usual process by which wings produce lift.