Dave
Pax! My "spend a few minutes actually thinking about what I said " was addressed to berkeman after his put down. It was not addressed to you!
Your comment was reasonable and, as you see, I agree with you. I have no disagreement with you - my disagreement is with berkeman not with you -...
I agree - "suck" is a useful concept to work with.
But it is as well to understand what is actually happening whenever one resorts to a concept which isn't actually totally true. Archimedes Principle is a useful concept but the unwary will fall l into trap after trap if she uses it blindly...
Please withdraw that comment before I report you to a moderator. You have no knowledge of my academic qualifications nor of my expertise. Neither is relevant here. I seem to recall Einstein was a patent clerk when he upended the scientific world.
May I suggest you carefully read what I said before contradicting me. I said " How can the fan blade possibly affect air molecules to the left of it? It cannot attract them by gravity, electrostatic, electromagnetic means or by any other force. ".
Can you perhaps tell us all how a molecule...
There is no such thing as "suck" when applied to a fluid or gas.
Say a fan is set up to blow air to the right. How can the fan blade possibly affect air molecules to the left of it? It cannot attract them by gravity, electrostatic, electromagnetic means or by any other force.
What a fan does...
The engineers are correct. Let's do a simple calculation.
Imagine, for simplicity, the bridge is a footbridge and it is 1m wide and 1m deep and made of concrete.
Concrete weighs about 2,500 kg/m^3 so a 1 metre length of the bridge will weigh 2,500kg.
See the diagram below where the angles...
Use two car? lorry? headlight reflectors? Army surplus searchlight reflectors would be good.
The bigger your energy source the bigger the reflector should be - a parabola only produces parallel rays for a point source.
Is there a health hazard of being struck by a 250W beam? In the eyes?