8,087 reputation
1728
bio website en.wikipedia.org/wiki/…
location United States
age 70
visits member for 3 years, 7 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.


2d
comment Do rotating non-circular projectiles also experience Magnus lift?
Almost any method of inducing circulation produces lift by deflecting the airstream. Simple example: take a strip of paper 1/2" wide by a few inches long. Hold it the long way between your hands and drop it, with backspin. It keeps backspinning and glides quite nicely.
2d
comment A moving brush on a vibrating surface
I suspect where the bristles touch the surface not completely vertical there is a ratchet action.
Apr
22
comment Why is the water in a cup not inclined (opposite the cup) when the plane takes a turn?
Because planes don't turn the way cars do, they turn the way bicycles do.
Apr
20
comment When we are inside a plane and look outside the window why does everything (outside) appear to be at rest?
When you see movies about flying, they try to make it exciting by zipping in and out between clouds, so you get a sense of speed. In real flying, you want it to be as boring as possible. You stay far away from clouds, and everything else, if you have a choice. Clouds are bumpy, they block your vision, and other planes can be hiding in them.
Apr
17
comment Why is wave a function of volts?
@user78162: Sure. You could go to an electronics store and buy a cheap voltmeter. Actually, what it measures is current through the little coil attached to the needle, but there's a resistor in series, so if you want to measure voltage, it does so. The trouble with a multi-meter is the needle is mechanical and can't move very fast. An oscilloscope trace can move faster and also show you the trace over time, that's all.
Apr
14
comment Why do we use capacitors when batteries can very well store charges?
I see your point.
Apr
14
comment Why do we use capacitors when batteries can very well store charges?
But if you time-integrate the current going into a capacitor, and coming out the other side, can't you call that "charge"? $I = dQ/dt$
Apr
13
comment Why pouring milk from a height makes a chain shape?
@Tarek: I think he means "chain". The cross-section of the stream is not circular, it is more like elliptical, and the long axis of the ellipse oscillates, so from the side it looks like a chain: o-o-o. I think it's a great question.
Apr
9
comment Static pressure in relation to CFM
I would look up orifice flow and work from there.
Apr
8
comment Is it correct to say “like poles attract, unlike poles repel” while two magnets are placed such that one is inside another?
A solenoid coil is not like a bar magnet. It is like a sleeve around a bar magnet. The magnetic lines of force go down the inside and up the outside (or vice versa).
Apr
8
comment Can universe or anything be simulated with absolute accuracy?
@LifeH2O: Even if the hypothesis of copying the universe were possible, quantum randomness would make them diverge. Take a simpler example: two entangled electrons with opposite spins. As soon as you learn the spin of one you know the spin of the other, but from that point on, they evolve independently.
Apr
8
comment Can universe or anything be simulated with absolute accuracy?
@LifeH2O: That's a problematic hypothetical.
Apr
7
comment The velocity of air on an airfoil
The best site I know on how wings work.
Apr
1
comment Roughness of the Surface and the time that a toy hovercraft hovers?
When you say "hovercraft" you mean something that floats on a cushion of air within millimeters of the floor or whatever it is hovering on, right? Then it all depends on the seal around the edges. The more air that gets out, the more power it takes to refill the air cushion, so the shorter the battery life.
Apr
1
comment Does a force being applied in an ideal case to an object of infinite mass where there is no friction always result in an acceleration?
$F=ma$ so $m=F/a$. You can talk about infinities and zero-divide if you like. Seems a little silly.
Mar
30
comment Since Earth spins, would an aircraft travelling opposite to direction of Earth spin take less time?
When I hear "why or why not" my homework-detector goes off. Regardless, if you can fly above the atmosphere and fly west toward that point, you will get to it sooner because it is moving east. Of course, if it's on the equator, you could simply get above the atmosphere and wait 12 hours, and it will come to you (though that means you are traveling west with respect to the earth at about 1000 mph). Anyway, if you're flying in air, which is basically attached to the earth, the spin of the earth makes no difference. It's just a matter of wind.
Mar
26
comment Is Magnus effect a corollary of Bernoulli principle?
It's not energy conservation along a streamline. It's momentum conservation along a streamline. It's $F=ma$, which is momentum conservation.
Mar
26
comment Why does a propeller suck in air from the front?
I bet your question comes from the standard wrong explanation of how wings work, the explanation that fails to account for downwash. Let me direct you to my favorite site for explaining how wings work.
Mar
21
comment How can a petrol car require less fuel at 55mph than a lower speed at the same rpm?
Just drive the car in first gear for an hour, it doesn't need much gas, but it doesn't go many miles either, so the miles per gallon is low
Mar
19
comment Is Physics being formally documented somewhere?
Actually, if there were a centralized database of physics knowledge of "immutable concepts", it would be a great resource for me and others who like to show where some such concepts are wrong :)