Originally Posted by Discovery Channel Press Release
"MYTHBUSTERS" CONTINUES TO MAKE SCIENCE COOL WITH SEVEN ALL-NEW EPISODES BEGINNING OCTOBER 31...
(Weds., December 12 at 9 PM ET/PT)
Adam and Jamie find out if either of them can safely land a Boeing 747-400 on a runway in varying weather conditions. Meanwhile, Kari, Tory and Grant risk life and limb to investigate skydiving myths regularly featured in Hollywood action films. Is it possible to catch up with someone in freefall if that person jumps out a plane before you do? Can you really hold a conversation during freefall? And would you survive if you opened your parachute only a few feet off the ground? Finally, Adam and Jamie carefully navigate their way through a myth that has baffled everyone from web bloggers to pilots. If a plane is traveling at takeoff speed on a conveyor belt, and the belt is matching that speed in the opposite direction, can the plane take off? Extensive small-scale testing with a super treadmill and a nearly uncontrollable model airplane don't completely resolve the myth, so our flight cadets supersize the myth with help from a willing pilot and his Ultralight flying machine.
Absolutely every physicist/expert/anyone who looks at the facts concludes that the plane will take off. The only people who argue otherwise are deluded by what they think is a more difficult concept to understand.
"If a plane is traveling at takeoff speed on a conveyor belt...."
Everyone seems to think that this means the place is travelling at takeoff speed relative to the conveyor belt and hence stationary relative to the ground. It's actually travelling at take off speed relative to the ground, and hence (2 x take off speed) relative to the conveyor belt.
To be honest, I think the confusion is entirely due to the appalling wording of the original question - you can't blame people for getting the wrong answer if the question's been mis-understood in the first place, they're just not going to get it right. Make it clear that the take off speed is relative to the ground, and everyone's a winner.
That's was my moment of realisation anyway, it became clear it would take off after that bit was explained to me.
Originally posted by uzless The plane is NOT stationary. It is moving forward at the regular take off speed
Exactly - why can't the question say that?
If I said I was running on a treadmill (= conveyor belt) you wouldn't take that to mean I was moving relative to the ground, and hence double "normal" speed against the treadmill. You'd read it as me running at a speed relative to the treadmill and stationery relative to the ground.
The logical/normal way to read "moving at take off speed on a conveyor belt" is to assume that it is stationery to the air/ground.