Airplane on a conveyor Again

My 2 cents on the subject (using actual demonstration)
This video is to answer the question of whether or not equal forces of the plane and the conveyor will cause the plane to remain stationary to the static air.

Category:

Education

Tags:

• physical
• science
• engineering
• logic
• education
• experiment
• airplane
• plane
• conveyor
• treadmill
• myth
• busters

[ZeroG84]

If you have both the plain and the runway connected to the same pully system, how in the hell does that make them "isolated". blah... kitchen table physics fail.

[Gaffeghan]

@ZeroG84 Troll fail - the pulley system is to ensure that the plane and the conveyor are both moving at the same speed. The isolation - and this is the tricky part - comes from the wheels, which dissipate friction. That means the plane and the conveyor are not going to act on each other in any meaningful way. Stay in school kids.

[petem1989]

An aircraft's motion is measured relative to the air, not the ground. As the thrust acts on the air, not the ground, the plane can take off normally, since the conveyor belt has no effect on the airspeed of the plane. Prop pushes back on air, plane moves forwards. The only effect of the conveyor is that the wheels will rotate at twice their usual speed.

[bob173rd]

Forces are equal but isolated...really...COOL!

[Gaffeghan]

@btankful "A plane is placed on a conveyor belt as long and as wide as a runway. As the plane moves forward, the conveyor matches it's speed in the opposite direction. Can the plane take off?" How is the premise misinterpreted in my experiment? If the conveyor accelerates at the same rate as the plane, the plane moves forward and the wheels spin twice as fast as normal.

[btankful]

@Gaffeghan By definition, speed of the plane is MATCHED by the ground. Granted, after inertia+friction, very little thrust needed to go forward. Wheel and ground are as good as two gears (until liftoff). One revo, 3 feet ahead. Each small throttle up (thrust) can be countered by much conveyor spin. It takes a lot of ground movement, yes, but conveyor is Infinite. It keeps this up until thrust is maxed. Forward plane only means it is NOT matched by the ground. Misinterpreted original premise.

[Gaffeghan]

@btankful The whole point of the car powering both is to ensure that the plane and the cloth move at the same speed. Since the wheels are there to isolate the plane from the ground (or conveyor), the plane is not resisted by the conveyor at all. The cloth does match the speed of the plane, but in the opposite direction. You're complaining that I didn't do what I did do. You're second leap of logic is erroneous. The speed is matched, and the result is that the plane takes off anyway.

[btankful]

@Gaffeghan Please. We all know the power is not from the wheels. Original puzzle creator wants you to make two leaps of logic. One, prop thrust not wheel power. Two, if conveyor is unlimited it can always Match speed of plane negating forward motion. It's a mind trap for those who stop after the first. "Getting it" is not picturing that even with extremely fast wheel spin, 1% inertia/friction is overcome with 99% thrust left. Again, cut your string, Match cloth with plane SPEED. No motion.

[Gaffeghan]

@btankful You're under the misconception that the plane moves forward on ground because of the wheels. In fact, the plane only moves because of the propeller (or jet engine). The wheels you speak of are only there to allow the plane to roll on the ground. The propeller is what is moves the plane. The experiment shows that even when the speed of the plane and the speed of the conveyor are equal (thanks to the car), the plane still takes off.

[btankful]

Too stupid for words. It's isolated. Exactly. All this shows is you've got a string from car to plane. Remove cloth. It still moves the plane to the end...... It's not forces. It's distance. On real runway, 3 foot circumference wheel moves the plane forward 3 foot in one rotation. With mythical conveyors, you take away rotation and forward movement. Conveyor (not plane thrust) is unlimited. It can always match plane (not wheel) speed. Thrust is not Lift. Plane in place. No wind. No Lift.

[taledarkside]

shouldn't the experiment be on a 50 foot long belt. Since a plane on a treadmill isn't going to make the distance it needs to travel to gain airspeed shorter.

[alexanderssson]

@petem1989

You are totaly right. However, both particles are moving, so we have Airplane speed + belt speed. Nevertheless, the air play an important role in the experiment as you stated;thus, I not only agree with you but also i believe that the conveyor belt and the wheels play an important role in the case.