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Jan
9
comment 2D - What is the next point given a start point, velocity, yaw rate, acceleration, and time change?
@StephenT.Robbins: I just realized, it $d\theta/dt$ is constant, that means $dr/dt$ is constant, so $dv/dt$ is constant, and that's your constant acceleration. So yes, the spiral is Archimedean.
Jan
8
comment How does an anti-g overall work?
@EdYablecki: There's a lot going on inside the cabin when a car collides. What does a head weigh - 12lbs? That's a 500lb force being applied for a fraction of a second. Ouch. And that doesn't count the rest of the body. Without air bags and seat belts, it's a "life changing event".
Jan
8
comment 2D - What is the next point given a start point, velocity, yaw rate, acceleration, and time change?
@StephenT.Robbins: I'm tempted to say Achimedean spiral where radius is linear in $\theta$, but I'm not sure.
Jan
8
comment How does an anti-g overall work?
It makes a difference if the person is sitting or supine. If sitting, the need is to prevent blood flow away from head to lower extremeties. If someone is floating in water, and the person + water is subjected to high-g, they can tolerate more.
Jan
8
comment 2D - What is the next point given a start point, velocity, yaw rate, acceleration, and time change?
OK, this is like a car. Now the constant rate of turning. Acceleration comes into play. Do you mean the steering wheel is held at a constant angle, so the front wheels are at a constant angle, so there is a fixed center about which the car is turning, in which case the curve is a circular arc? Or do you mean that as the speed increases the steering wheel is turned back toward 0 so as to keep the yaw rate constant? Just trying to clarify the question.
Jan
8
comment 2D - What is the next point given a start point, velocity, yaw rate, acceleration, and time change?
Is this vehicle like a car with wheels, so it cannot slide sideways, or is it like a rocket, that can go sideways?
Jan
5
comment Can the Arcaboard fly?
@SamuelWeir: I'm skeptical too, but control does not look to me like an issue. You can just tilt it with your feet, to turn it or let it accelerate horizontally.
Jan
4
comment How Vision Works
Good place to start.
Jan
2
comment Why does moving air have low pressure?
Here it's more explicit. The air being deflected downward is not just the air below the wing, but also the air above the wing. In particular, anything that disturbs the flow on top of the wing, like a thin layer of frost, kills lift badly. Big cause of accidents. Also this. Note emphasis on top of the wing.
Jan
2
comment Why does moving air have low pressure?
Ummm... Last sentence? Try reading this.
Dec
31
comment Driving on the moon
++ Yes. But if your runway took the form of a helical loop which then exited upward, you could do it :)
Dec
18
comment Equal transit fallacy in viscous materials
@Bob: Here's a very good and easily understood explanation. Essentially the flow is a summation of linear and circular motion (a vortex) resulting in the downwash. If the molecules rejoin there is no vortex. No vortex = no downwash, and no downwash = no lift.
Dec
17
comment Remove measured distribution from another distribution
Good question. You might want to ask it on Cross Validated.
Dec
16
comment Aircraft lift theory vs energy conservation
Drag is a function mainly of speed and angle of attack, and other variables. I can't recommend a better source of information than this. Also, the 747 is very efficient aerodynamically, as are all jet transports. This can be seen in their glide ratio, the angle of their descent under no power. A typical glide ratio for a jet transport is around 25:1, while for a Cessna 172 it is only around 9:1, in a clean configuration. If landing gear, flaps, or spoilers are out, it is a lot less.
Dec
16
comment How is momentum conserved when is is only dependent on mass and velocity, and so many other factors come into play?
@AdamGraehling: You're talking about momentum, not energy, so forget about heat and deformation. Those are conservation of energy, not conservation of momentum. In your example, when you say "no external forces act", that means no friction, like if the cars are on a greased surface. If so, the cars will not stop after colliding - the pileup will continue moving at the same speed as their center of mass did before.
Dec
15
comment Why current loses its energy?
Google electrical resistance.
Dec
14
comment What makes bathroom soap bars to crack during winter season?
@nemu: Just guessing - put a bar of soap in a cool oven? Travel to the nearest dry lake or river bed?
Dec
13
comment why is pressure more convenient than force while dealing with fluids?
These questions are very elementary. You want a general understanding of fluid statics. Think of a cube of fluid as full of bouncing rubber balls, and the walls are vibrating too (with temperature). That model answers all your questions.
Dec
12
comment How does gas spin the turbine in a jet engine?
@Ethan: Do you have trouble understanding how a table fan works, or a propeller on a boat? Failing that, does a paddle on a canoe make sense to you?
Dec
10
comment If quantum tunneling is possible, is there a maximum thickness of material a particle can go through, and is it random?
+ I like your explanation but I don't see something that helped me understand it. Before entering the potential barrier the wave function takes the form $e^{-ix}$ so it is cyclical, but in the barrier the exponent becomes real $e^{-x}$ so it is an exponential decay (or something like that - I'm rusty on this).