Yeah that was stupid, i worked out the opposite driving force for a rocket is gravity, and some air resistance.
I wasn't thinking properly.

EDIT: reading your post again. There is more air resistance force than i thought. Maybe even more than the gravity effect ? as speed increases so does the density of the air you are pushing. and a rocket going at 6000mph.... lol

No it wont stop.

It will take off in an even shorter distance.
Because you would get even more air going over the wings.... = more lift.

BUT what im saying is the opposite

if the wind was from behind the plane. the same speed as the plane is going forward, it would NOT take off.

It would move forward at 100mph or what ever but it would not take off. Because the air would be effectively going 0mph over the wings. Therefore creating no lift.

Same as the car on the conveyer belt in principle.

If a plane is capable of traveling at 100mph, then in a 100mph back wind, a plane will travel much faster since there is no air resistance. Thus a plane will naturally accelerate past 100mph and eventually taking off.

Say this particular plane needs to go 100mph on a windless day to take off. Its top speed is also around 100mph. ( a crappy little Cessna or something :P) (maybe it can go 20mph faster with the lack of wind resistance.)

It would need to go 200mph to take off. It is impossible for it to do that. The back wind will not make it go 100mph faster than its top speed. (when you go running with a 20mph wind behind you, you don't run 20mph faster than normal.)

The plane would need to travel at 200mph to take off with a 100mph back wind. (because it requires 100mph of air over its wings to produce sufficient lift)

It is exactly the same as the Car on a conveyer belt. But different forces.

EDIT: made post make more sense.

If a plane is capable of traveling at 100mph, then in a 100mph back wind, a plane will travel much faster since there is no air resistance. Thus a plane will naturally accelerate past 100mph and eventually taking off. One needs to think about relative speeds here, though. The plane's "speed" needs to be relative to the air for it to achieve lift, whereas the wind speed most people tend to refer to is relative to the ground. If the plane is static and accelerating to takeoff, a tailwind of 100 mph will require the plane to do considerably more than its normal minimum take-off velocity as the air flow is essentially in the wrong direction. Mind you, at 100 mph of tailwind there's a good chance that despite the angle of attack being all wrong, there's sufficient air speed to generate lift!

The plane in question needs to travel at 100mph on a windless day to achieve enough lift to take off.
Its top speed is also around 100mph. ( remember its a crappy 2 seat small prop plane)

So a tail wind of 100mph would make it IMPOSSIBLE for the plane to take off ?

the plane would need to go 200mph to create the lift it requires wouldn't it ?

Which would make taking off impossible.

It seems to be correct in my head.. i dunno :/ lol ?

An airplane traveling at 100mph with back wind of 100mph, would be same thing as a plane standing still with 0mph wind. Right?

Unless Cessna's top speed is limited to 100mph, then it would not take off with 100mph back wind or it might still take off, as the wind it self would cary the plane in the same direction.

Yeah that's right. So technically it would need to move forward at 200mph

But a 100mph back wind will not make it go to the 200mph it would need. So it is impossible for it to take off.

When you go ruining for example, you can run at 10mph. With a 10mph wind behind you, it does not mean you can suddenly run at 20mph.

You and i have a limitation not only do to wind resistance, but do to human power, and running is measured only by ground speed. Air speed is different. .. i think. If i'm right, then the plane would take off at some point.

No it wouldn't. The wind behind it at 100mph would not add another 100mph to the top speed of the plane to make it go the 200mph it requires to be able to take off with the wind traveling 100mph behind it. If that makes sense lol.

Maybe the plane would go at a slightly faster top speed, say 120mph because of the less dense air in front of it than normal. But it would still not be able to get 100mph of air to go over the wings to create any lift.

EDIT: actually thinking about it, it would probably not even go any faster at all, because of the air being less dense in front of the plane that means the propeller will have less trust than normal. So it cancels out any reduction in air resistance.

wait wait wait.

If a plane traveling at 100mph with 100mph back wind is same as a plane traveling at 0mph in 0mph wind, then why wouldnt it take off?

Because there is no air going over the wings at any speed in the correct direction. So there is no lift created.

A plane needs air to travel over the shaped wing at speed to generate lift. The air that goes over the top of the wing takes longer to go over it than it then the air that goes under the wing because of its shape, thus creates low pressure above the wing and higher pressure below the wing, and it is essentially sucked, or pushed up wards.

Right. A plane that is not moving cant take off.

So then the plane would reach 200mph ground speed, or 100mph air speed to take off. right?

Funniest thread on here in quite some time. Keep it up! [rofl]

Found a perfect explanation. And if i plugged in the numbers correctly, then a plane would not take off.

http://www.grc.nasa.gov/WWW/K-12/airplane/move.html

some one double check the math.

Don't forget that the earth is rotating over 1000mph http://www.discussworldissues.com/fo...ies/laugh1.gif

If an airliner is flying at 550 miles/hour and, instantly, there is a gust of wind heading directly towards the front of the plane equal to the speed of the plane, does the plane stop moving?

If a horse is running at 25 miles/hour and a wall, running at 25 miles/hour, collides with the horse; who wins?

100mph tail wind? is the pilot trying to escape one of the most powerful hurricanes. 100mph winds are conditions you'll find in the eye of a storm, obviously enough you wouldnt be taking off in these conditions.
A small crappy 2 seater could take off at a ground speed of we'll say 50mph, if then there were a tailwind of 50mph, yes it would need a relative ground speed of 100mph (effective 50mph airspeed) to take off and would probably need 10 times or more the runway length to do so, and waste a lot of its fuel at full throttle. Having that said it would take one crazy pilot to even attempt such a take off. 15mph tailwinds are dangerous enough for smallcrafts to land or take off as inital climb speed will also be less and descent speed will be greater

Of course its a different story when the plane is already in the air and is travelling with (a tailwind) a moving air mass like a jet stream. however the reverse of this (travelling against the air mass) is counterproductive, yes the airfoil generates more than enough lift without the need for forward momentum but you basically just hover in the air so your relative ground speed is effectively zero and you get nowhere

No, not within the air mass, but its effective ground speed would eventually be reduced to zero. thats why planes do not fly against the wind in jet streams

Depends on the mass of the 2.

If they were the same mass as each other then it means each object hitting each other at 25mph head on would each receive the same damage as if they each it hit a solid wall at 25mph.

2 cars hitting each other head on at 60mph, is the same as one car hitting a solid wall at 60mph.