meta user
network profile
| bio | website | en.wikipedia.org/wiki/… |
|---|---|---|
| location | United States | |
| age | 68 | |
| visits | member for | 1 year, 8 months |
| seen | 6 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)
|
May 4 |
comment |
Why do focal lengths affect magnification? @articlestack: Suppose you have two stars, where the angular distance between them is .01 radian. Then if you have an objective lens that focuses them to an image plane, how big is the image of the two stars? It will be .01 times the focal length, right? 10cm -> .1cm, 100cm->1cm, 1000cm -> 10cm. So then if you look at that image plane with a keplerian eyepiece (magnifying glass), you're examining a small piece of a bigger image. |
|
May 4 |
comment |
Will a helicoper which is hovering inside a closed box move with the box when we move it? The helicopter is not independent of the air - it is suspended in it. (Pilots care about that, needless to say.) If the air accelerates upward (say) the air will soon have an upward velocity, creating more lift, causing the helicopter to accelerate upward after a time lag. Same goes for acceleration in any direction, but you're right that if the box is small the 'copter will probably hit the wall in that time lag. |
|
May 3 |
comment |
Solving a simple equation Sounds like you need the quadratic formula. |
|
May 3 |
comment |
I read a book saying bernoulli's flight equations didn't have as much impact on lift as most people think @user1247: Please read. |
|
May 3 |
comment |
Why do focal lengths affect magnification? @articlestack: Wikipedia |
|
May 2 |
answered | Why do focal lengths affect magnification? |
|
May 2 |
comment |
Are the hypotheses of the Bernoulli equation satisfied for a bird or airplane wing at low Mach number? @Ben: Right, as you get to Mach numbers above maybe 0.5. |
|
May 2 |
comment |
Enginering question about F1 car Actually the speed is far in excess of small planes. |
|
May 2 |
comment |
Enginering question about F1 car + The only problem with these pictures is they seem to imply by the arrow heads that air parcels separated by the leading edge are rejoined at the trailing edge (the equal-time assumption). In fact that's not so, and the wing wouldn't work if it were. Check here. |
|
May 2 |
answered | Are the hypotheses of the Bernoulli equation satisfied for a bird or airplane wing at low Mach number? |
|
May 2 |
comment |
I read a book saying bernoulli's flight equations didn't have as much impact on lift as most people think + You're right to say "produces lift by directing air ... downward". You're not quite right to de-emphasize the Bernoulli effect. The page Michael Brown linked to explains it quite well. You can't really separate the downwash effect and the Bernoulli effect. The only problem with the Bernoulli effect is that it's badly taught. |
|
May 2 |
comment |
Determining the length of a Torsional Pendulum It sounds to me like a plain-old pendulum. It is swinging at a frequency of 5.72 radians/second or about .9 swings per second, and it started from an extreme position. It's maximum angle of swing is .14 radian or about 8 degrees. |
|
May 1 |
comment |
Would there be any possibility for anyone to survive when a Boeing 747 crashes to pacific ocean with its normal cruising speed? Pilots train for dead-stick water landings, as in US Air 1549. Size of the aircraft is not a factor. |
|
Apr 26 |
comment |
Why is the damping force on a spring oscillator linearly dependent on velocity? Cars these days have shock absorbers that are basically dashpots with viscous drag. There was a time when cars used straight friction devices to absorb the energy in up-and-down wheel motions. It just depends what type of energy-absorbing device you use. |
|
Apr 26 |
comment |
Why don't we see solar and lunar eclipses often? @Firzen: The new moon is visible during the day, provided you can block out the glare from the sun. This is most easy to see just after sunset or just before sunrise. |
|
Apr 25 |
comment |
Equilibrium of a sphere in a water tank To put @JohnRennie's comment another way, suppose the hole is obstructed by a circular stopper, held there by the weight of water above the hole. Then assume the sphere is trying to float but is tethered to the stopper. You want to know how much bouyancy it needs to just barely lift the stopper. |
|
Apr 25 |
comment |
Wind effect on driving a ground-based vehicle + for the wig :) |
|
Apr 25 |
answered | Wind effect on driving a ground-based vehicle |
|
Apr 22 |
comment |
Production vs. Collection, and Contaminants vs. Depositions, what might be missing in cold fusion research @user23467: If I were you, I would edit it in place, making it clean and to-the-point. I would also not beg any premise, such as "given X is impossible". Another course of action would be to delete the question, read everything you can find on the subject, and then maybe ask another question. |
|
Apr 22 |
answered | Why wasn't the moon visible during the day a few decades ago? |
