7,778 reputation
1628
bio website en.wikipedia.org/wiki/…
location United States
age 70
visits member for 3 years, 3 months
seen 3 hours ago

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.


Dec
16
comment If an airplane is flying sideways, is it in free fall?
@Vivek: There's a maneuver called a knife edge where the wings are at 90 degrees to the ground. What the rudder does is put the fuselage sideways to the wind, generating the lift that holds the aircraft against gravity. Generally any such use of the rudder is called a slip or skid.
Dec
16
comment If an airplane is flying sideways, is it in free fall?
@Vivek: Yes, but would you call it free-fall? The pilot could be pulling 4G or more in that horizontal direction.
Dec
15
comment Can the weight of a bird be measured, considering air friction?
@Santhi: It comes out as extra air pressure on the bottom of the box. The wings get lift by pushing air downward, which hits the bottom of the box, which pushes the air back up so it stays in the box. That means the bottom of the box is feeling more pressure.
Dec
11
comment Does juggling faster less work then juggling slower?
Before you hoist a ball to a height, it falls into your hand from the same height, so in principle it takes zero work for any height. So it all depends on how efficient your muscles and joints are.
Dec
10
comment Where can I get fluidics components?
Excellent question, though some may think it is off-topic for physics. If I were you, I would start thinking about 3-d printers.
Dec
8
comment How to approximate lag of roll of a bird (or RC airplane)?
@Yeti: You're probably only able to estimate an approximate value. There's guesswork no matter how you do it.
Dec
3
comment Gravitational field intensity inside a hollow sphere
I like Qmechanic's answer, but my own intuition is this: suppose the shell consists of a lot of small "moons" covering the shell. You could be close to one and feeling its gravity, and the ones "across" the way have gravity that falls off at $d^2$, but the number of them increases with $d^2$, so they are just as powerful as the one you are next to.
Dec
3
comment Calculating the force required to lift a weight with a screw
He's ignoring friction, so it's just an energy balance. The energy put into lifting the weight is what? 2000 lb * 1 inch = 2000 inch-lbs. That handle must be pushed 1260 inches to get the same energy, and 1260 inches * 1.6 lb ~ 2000 inch-lbs. What's this dimensional analysis you're talking about?
Dec
2
comment Why is a thought experiment a valid way to prove anything?
@Albalma: Next to Feynman's lectures, this is my favorite book on relativity. The author was teaching relativity in a continuing-ed class where people were math-phobic, so he does a great job of making it accessible.
Nov
30
comment Why is a thought experiment a valid way to prove anything?
@Albalma: I agree - dogmas and stigmas are bad things. I'm in favor of skepticism. Not only questioning of positive results, but questioning of negative results. A perfect example is "cold fusion". If on the other hand you're talking about global warming, skepticism is a good thing, but using it as an excuse to do nothing and just let the hammer fall is poor wisdom.
Nov
28
comment Why can't we fly?
We can fly
Nov
25
comment When an aircraft flies over, glass window vibrates…Infrasound?
Just my guess - there's no reason the noise can't go into frequencies below what you can hear (about 20 hz). Of course if it makes your windows hit their frames, those clicks will be at a higher frequency so you can hear them. Nothing strange about that.
Nov
22
comment Torricelli with constant vertical drain speed
I don't understand the question.
Nov
21
comment Why are flight feathers asymmetric?
I'm guessing it's to match the pressure distribution, which is greater toward the leading edge. Whether the wing is swept back or not is not the issue.
Nov
13
comment What exactly are light waves?
It's a good idea to study Young's double-slit experiment. I like to think of it as a wave of alternating electric and magnetic fields, but it also acts as a probability amplitude wave of a photon appearing. So when the waves interfere, they're changing the probability of photons appearing.
Nov
11
comment What prevents this rotational perpetuum mobile from working?
The two red wheels at the bottom are turning against each other. If they have friction, them all the kinetic energy turns into heat energy. If they are gears, then the wheels can't even start. $w_1$ has nothing to do with it.
Nov
7
comment Trajectory of a bomb dropped from an aeroplane
As @Omen said, we're trying not to be a homework completion service.
Nov
4
comment hydrodynamic entrance length [developing flow]. Non-native speaker needs some help
I think your English is not bad. I think the sentence is fairly clear, although I don't understand the content.
Oct
30
comment Fluid flow through an orifice
You say you know the area of the orifice, but it does not have constant diameter. That's confusing.
Oct
29
comment How to prevent water droplets becoming larger on the tip of a nozzle?
@Meriam: Related: Kelvin's water dropper.