Wikipedia is your friend.

 

Sure, about the "V" for a plane, but that's not achieved while still in contact with terra firma nor powered through the wheels? I really like the European trains, and the Franch have taken the lead.

 

Now you might want to avoid QM. It has caused arguments amongst the greatest thinkers of the 20th century.
"God doesn't play dice with the universe" A. Einstein

On Topic. Having flown on the Concorde, sign me up for 350mph train.

 

It's a good thing that no one has compared the French quest for the best trains to a war ... they'd have surrendered at the earliest opportunity

 

 

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For the most part. Nice explanation Mike.

If I may clarify or elaborate on Mike's explanation. (Jerry will love this thread killer information) The takeoff speed for a given model airplane (I.E. Boeing 747-300) will not vary based on it's weight (800,000 pound maximum). The rotation speed is 155 Knots (180 MPH). That is a constant. The factors that affect how quickly a plane with reach it's rotation speed and therefore how much runway it uses (given that it's trust to weight ratio remains constant) is ambient temperature that not only effects engine performance as cold air is denser than hot air. But colder air is denser and provides more lift than hot air. The other factor is the head wind. Planes always take off and land into the wind. The wind speed of the head wind will determine how quickly the plane reaches its take off "Air Speed" (not ground speed). For example if the ground speed down the runway is 140 Knots into a head wind of 15 Kts the planes air speed of 155 Kts thus allowing it to reach it's rotation speed faster than if there was no head wind.

I was once on a chartered Lockheed Tri-Star L1011 returning from Reno, NV to LGA in NYC because of a unusual heat wave (103*F) for late September we could not take off with a full load of fuel due to the runway length required in that heat. We took off and flew to Las Vegas to take on the necessary fuel to make it to NYC.

I hope that this helps.

 

Very interesting, Matt. I guess that the opp of head wind woud be tail wind? So.....a plane never takes off or lands with a tail wind? I would think that a tail wind would add to the plane's speed and make for a quicker take-off? Or maybe a tail wind is unstable

 

A tail wind increases a planes ground speed, not air speed. Air speed is what is needed to generate lift. If one thinks about the Benoulli effect that allows a wing to generate lift is the tail wind was strong enough it would reduce the planes air speed relative to the wind flowing over the wings and could cause the plane to stall.