Mike Dunlavey
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 Jan 20 comment Non-determinitric flow of water stream on vertical porcelain surface There's probably a better answer, but the water streaming down the surface has surface tension, that apparently affects it chaotically, the same way rivers meander. Flow in a straight line is unstable, because the slightest curve tends to grow on the outside. Jan 13 comment Mirrors into Infinity + Nice, and you get a similar effect if you have 1) a TV camera, connected to 2) a closed-circuit TV monitor, and 3) the camera is looking at the monitor. In the 70s this was an example of electronics "freaking out". Jan 12 revised Homopolar motor and Lorentz force edited body Jan 12 revised Homopolar motor and Lorentz force added 571 characters in body Jan 12 revised Homopolar motor and Lorentz force added 571 characters in body Jan 11 answered Homopolar motor and Lorentz force Jan 11 comment Homopolar motor and Lorentz force + I'd never seen that before. What a nifty demonstration! If you have a wire cutting through magnetic field lines a current is induced. Then the reverse has to be true also, and that's what you're seeing. Jan 11 comment How does the pressurization in a house's water supply allow adjustable flowrates from a tap? I'm sure you're learned in your Ph.D. studies in fluid dynamics that pipe networks and wire networks are analogous, and an adjustable tap is just like a variable resistor. Jan 8 comment Pressure difference between 2 side of wings of aircraft @shortstheory: This is my favorite explanation of all that. Jan 6 comment Spontaneous motion in a wind tunnel @GoodarzMehr: At low mach number (ignoring compresibility) conservation of mass says $\rho A_1V_1 = \rho A_2V_2$, so momentum/second in equals momentum/second out, so no net thrust. (Ignoring drag on the cone.) Jet engines work by increasing $V_2$ by expanding the gas. Jan 6 answered Spontaneous motion in a wind tunnel Jan 6 comment Would Beetee's electrocution plan work and kill the tributes in the lake? If people are in the lake, they are basically conductors, being largely made of salt water, insulated only by a little layer of wet skin. Jan 6 revised How to optically rotate images in small increments (for eyeglasses)? added 550 characters in body Jan 6 revised How to optically rotate images in small increments (for eyeglasses)? added 550 characters in body Jan 5 revised How to optically rotate images in small increments (for eyeglasses)? added 18 characters in body Jan 5 answered How to optically rotate images in small increments (for eyeglasses)? Dec 31 answered How is NASA's mod II Stirling engine so powerful yet so small? Dec 28 comment Exactly how much lift is needed to overcome the weight of an average person? @User58220: It accelerates at 1g. Dec 28 comment Exactly how much lift is needed to overcome the weight of an average person? Aircraft have a rating - wing loading - expressed in weight per unit area. A typical small plane is in the range of 10lb/square foot, which is achieved at a speed of roughly 60 mph. Lift is proportional to speed squared, so if you halve the speed, you need 4 times as much area. Dec 26 comment Is there a travelling speed of for electric field? If yes, what is it? In a vacuum, you're right. Inside a metal wire, it is different, as the other answers and comments are discussing.