8,024 reputation
1728
bio website en.wikipedia.org/wiki/…
location United States
age 70
visits member for 3 years, 6 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.


Oct
10
comment What is the power in this circuit if the voltage is doubled?
@Floris: You're right. I was doing back-of-the-hand physics.
Oct
9
comment What is the power in this circuit if the voltage is doubled?
Right. If you double the voltage across a resistor, that doubles the current. Double voltage times double current - four times power. If you're in the U.S. and you take a 100-watt light bulb built for 110 volts, and accidentally connect it to 220 volts, what happens? 400 watts - POP!
Oct
1
comment What stored charges do in a capacitor?
If the fan motor has brushes, the capacitor can prevent arcing.
Sep
29
comment What causes a spacecraft entering the atmosphere to catch fire?
Check Wikipedia.
Sep
29
comment When two objects roll down an incline, does the velocity increase?
Suppose their radii are 1cm and 2cm. Since it says they roll together, they have to have the same tangential velocity (i.e. zero at the point of contact, and 2V at the opposite point. The "axle system" must be one that turns the small one at twice the angular velocity (with gears). Since centripetal acceleration if V/R^2, the small one has 4 times the acceleration.
Sep
26
comment How does train back draft work
+ And if the train is long, it carries air with it along the sides, lowering the pressure, so pulling in careless creatures.
Sep
25
comment Time for water levels to equalize
Pouring in the quantity of water will start a surface wave, which travels at a speed depending on the wavelength (longer = faster), and as @John said, that depends on the depth. After a couple circumnavigations, the wave will dissipate, leaving the water deeper. Not a simple problem.
Sep
24
comment Modeling wall's behaviour
It's pretty simple. The tree is going to grow, and the wall is no match for it.
Sep
17
comment Movement of a cylinder filled with water
You might simplify it by replacing the water with a pendulum suspended from the centerline of the bottle. Then the bottle could be replaced by a little "frictionless" cart on a horizontal track at the level of the bottle's center.
Sep
16
comment What is a Physically Accurate Explanation for the Kutta Condition?
I'm struggling to follow this, but I'm very impressed (which doesn't mean much).
Sep
15
comment Is voltage difference always proportional to its derivative?
You're dropping off the C (capacitance) and R (resistance) parts. Everything depends on those.
Sep
15
comment Do all elements spectrum lines fall within the visible light range?
There are ultraviolet and infrared lasers.
Sep
13
comment Does the sun “drag the solar system through space”?
The video has very pretty graphics, however it doesn't really say anything. It says heliocentric motion and helical motion are different, but the difference is in perception only.
Sep
12
comment What happens to a photon after it is absorbed by an antenna?
Receiving antennas work because the electromagnetic wave excites EMF in the a antenna wire. It makes the electrons (or charge carriers) in the wire feel force and move. In so doing, energy is removed from the wave. When a photon of light boosts an electron from one orbit to the next, it is the same thing, but on a quantum level.
Sep
10
comment What are washers for?
@jnovacho: I'm under the impression that the cut in a split washer does two things: 1) apply spring pressure (so the bolt remains under tension so it won't loosen further even if it loosens a bit, and 2) to cut into the bolt head if it tries to rotate counter-clockwise. Note it is shaped to allow clockwise motion, but it resists counter-clockwise by digging in. (They are called "lock washers".)
Sep
8
comment A problem says : a car starts from rest and undergoes a constant acceleration. It travels 5 m in the…?
@Maher: Yes, its average speed was 5m/s, but it did not travel the whole distance at that speed. At the start of the second, its speed was zero, right? At the end of the second, its speed has to be larger than 5m/s, right? because it it was 0 at the start, and 5 at the end, its average would have to be less than 5, right? The average is 5, but the speed changes from 0 at the start to something more than 5 at the end, 10 in fact. Keep in mind that acceleration is the amount that speed changes every second. That's why it is meters per second per second.
Sep
5
comment Ways of finding average accelleration
Average acceleration is total change in speed divided by the time in which it takes place. If the speed is 0 to start with, and 3 second later it is 2.1 then, yes, the average acceleration is 0.7. However, that is average acceleration. If the acceleration was 2.1 for one second, and it coasted for an additional two seconds, the average over the 3 seconds would still be 0.7.
Sep
4
comment Static,total and velocity pressure at a point
@Bryson: The density is given, along with the volume. The area of the shaft entrance is given, so the velocity can be determined. Isn't that enough to determine pressures?
Sep
2
comment Will I be able to push a small object in front of me in the outer space?
You and the ball together have a center of mass. If you push the ball away, you will also move away, at a speed that keeps the center of mass in the same place.
Sep
2
comment Circular motion and time dilation
@AlanSE: The time dilation due to velocity alone is relative - each one sees the other as slower (special relativity). The time dilation due to acceleration is absolute - they both agree which one is slower (general relativity). That's how the twin paradox is resolved.