Will the plane takeoff?

[PARAGON]

Originally Posted by Wisha Haddan H3

True that a plane can't take off w/o airflow over the wings to generate lift.

So the underlying question is ... "can a plane generate forward motion (into the wind) on a runway that moves in the opposite direction?"

A car could not, because it generates forward motion by transferring energy to the ground, which would be negated by the conveyor's opposite motion. But a self-propelled plane could still move forward, because it accelerates by pushing the air, irrespective of ground speed or conveyor direction.

That really has nothing to do with it.

Wheels have to turn in either situation. In the case of the plane, it has to move relative to air to lift off, a car doesn't. That is the only difference. How they apply their power has no bearing on this riddle.

Even if a plane is "pushing the air" it has to push against that air (thrust) to make the plane move, gaining speed. As it gains that speed the conveyor is matching the speed in the opposite direction, same as a car would.

[Mrs.ssippi]

Okay I want to change my answer from yellow to 2:30 am.

[h2co-pilot]

It says that the conveyor will change speed according to the plane's. So it will not move via air or land.

[PARAGON]

There are 2 answers to this question.

[BlueHUMMERH2]

http://www.straightdope.com/columns/060203.html

[PARAGON]

Originally Posted by BlueHUMMERH2

http://www.straightdope.com/columns/060203.html

Hey thongboy, got something better than a link to some ignorant liberal columnist?

[BlueHUMMERH2]

Ok, fine, here's a link to another site.

http://www.newton.dep.anl.gov/askasc...5/phy05023.htm

[Wisha Haddan H3]

Originally Posted by PARAGON

There are 2 answers to this question.

Let's hear it

[PARAGON]

Originally Posted by Wisha Haddan H3

Let's hear it

Simple

Yes

and

No

[Wisha Haddan H3]

Originally Posted by PARAGON

Simple

Yes

and

No

Thanks for clearing that up

[Wisha Haddan H3]

Originally Posted by PARAGON

That really has nothing to do with it.

Wheels have to turn in either situation. In the case of the plane, it has to move relative to air to lift off, a car doesn't. That is the only difference. How they apply their power has no bearing on this riddle.

Even if a plane is "pushing the air" it has to push against that air (thrust) to make the plane move, gaining speed. As it gains that speed the conveyor is matching the speed in the opposite direction, same as a car would.

Somehow missed this post. On the contrary, how airplanes apply their power is central to this riddle.

For example, when we walk or run, our propulsion is based on applying force to the ground. We push backwards and resistance sends us forward relative to the ground and air. On a treadmill, our feet push the conveyor belt and all our walking force is spent keeping up with it. We feel no wind in our face because our speed (relative to the ground and air) is zero. A car, bicycle or any vehicle that uses ground propulsion would experience the same effects on a conveyor belt.

However, an airplane's engines don't push the ground. They apply force directly to the air. When the air pushes back, the plane is thrust forward through the atmosphere at ground level. The wing's movement through the surrounding static air creates lift and the plane takes off.

On a conveyor belt runway, the exact same process occurs ... the engines push air backwards and the plane is thrust forward through the atmosphere. The conveyor belt can spin all it wants to, but it will only make the wheels spin faster. It can't hold the plane back because it isn't attached to the plane. Since the plane thrusts directly on the air, it doesn't rely on the conveyor belt for propulsion the way a person or car would. Instead, it slices through the air and takes off when enough lift is achieved.

[PARAGON]

Originally Posted by Wisha Haddan H3

Somehow missed this post. On the contrary, how airplanes apply their power is central to this riddle.

For example, when we walk or run, our propulsion is based on applying force to the ground. We push backwards and resistance sends us forward relative to the ground and air. On a treadmill, our feet push the conveyor belt and all our walking force is spent keeping up with it. We feel no wind in our face because our speed (relative to the ground and air) is zero. A car, bicycle or any vehicle that uses ground propulsion would experience the same effects on a conveyor belt.

However, an airplane's engines don't push the ground. They apply force directly to the air. When the air pushes back, the plane is thrust forward through the atmosphere at ground level. The wing's movement through the surrounding static air creates lift and the plane takes off.

On a conveyor belt runway, the exact same process occurs ... the engines push air backwards and the plane is thrust forward through the atmosphere. The conveyor belt can spin all it wants to, but it will only make the wheels spin faster. It can't hold the plane back because it isn't attached to the plane. Since the plane thrusts directly on the air, it doesn't rely on the conveyor belt for propulsion the way a person or car would. Instead, it slices through the air and takes off when enough lift is achieved.

Not entirely true.

The plane has to gain distance over time. If the conveyor moves the plane rearward for every instance in time the plane's thrust attempts to move it forward, the net movement relative to the air would amount to zero.