I'M fine with the flat part , BUT

on a dyno the rollers are rolling in the direction the wheels are moving them ......... my conveyor rolls to make the wheels of the plane go BACKWARDS while the plane wants tomake em move FORWARD

so the dyno is not a good comparison apples to apples

 

d'oh you are right, i didnt think the dyno thru, they do roll in the same direction as the tires. i told you it would throw people off. Bad example. but the plane will still take off.

 

The conveyor has nothing to do with it. The wheels are irrelevant. The plane doesn't have to "move forward" at all to fly. The conveyor in this example does nothing but spin the tires at some irrelevant speed. It seems that the assumption here is that somehow the conveyor is inducing speed into the airplane. That could only happen if there was some sort of drivetrain that actually powered the plane forward through the wheels. The tires on an airplane could spin at 1000 mph and it still would go nowhere.

A plane will fly if the air speed flowing over & under the wings is sufficient to create lift.

I think you are getting hung up on a technicality (or it's a trick question & I'm mis-understanding it). I believe the intent is to state that air flows around the wings in the normal fashion that an airplane is designed for.

Ex:A theoretical planes take-off speed is 70 knots

The plane is sitting stationary, on level ground, neither the plane nor the ground is moving, but there is a 75 knot headwind. Let's say in this example that the front of the plane is on a tether that can move in a vertical direction only (like a flag-pole) so that it doesn't just get blown off the runway. This plane would take off.

 

The part of the conveyor is to try and get the plane to not take off, by spinning in the opposite direction, at the same speed as the wheels on the plane. The wheels have no drivetrain, only power is provided by the engine, producing the thrust needed. It can be a trick question because you can view the relationship between the conveyor and plane in different ways. if the conveyor is to move the opposite direction, the plane would have to move first for the conveyor to pick up the sense that the plane is rolling, and the conveyor basically would have to catch up. or, another way is to say the conveyor starts first, then the plane starts thrusting to compensate for the conveyor moving. Now the wheels can spin at an infinite speed, so no problem there. but the plane, being pushed by the thrust of the engine, would move, eventually, and take off.

Another example i read somewhere is this: take a treadmill in a gym, a pipe with a wheel mounted on it with a ball bearing (such as the landing gear on a plane is attached) have someone on either side, holding the pipe, when the treadmill goes, the wheel will spin in that direction, but the people on either side holding the pipe can move the wheel in the opposite direction if the treadmill. The people are the "Thrust" moving that wheel. nothing is holding that wheel in one spot on the treadmill, holding it there spinning, it is being pushed by force, much as the plane would move forward being pushed by the thrust of the engine.

 

the plane , in my mind , will take off ; if the thrust of the engines is greater than the resistance (conveyor)

you got to think that the Harrier takes off because the thrust bounces off the ground as the F-14's thrust bounces off the raised wall in back of it on the carrier deck .... it doesn't need it in the air to fly forward , but the wall / catapult / headwind / speed of ship multiplies the thrust + air lift to help take off on such a short distance . We call this torque : the initial push / power required to start moving an inanimate object ..... if its already moving : then horsepower is required to achieve greater speed , period .

picture this , you're holding the Harrier in your hand 10,000 ft in the air , you let go of it as you turn on the thrusters at full power ..... now don't tell me the plane will not fall below for who knows how long before the thrusters get the upper hand , if they ever do ................... now the solid ground (rebound) is the conveyor not moving ..... and the conveyor moving is the absence of ground (rebound)

now if there was no rebound , it would take mega mega power to create lift .; in the same way the resistance caused by the conveyor ; it will require more power to achieve lift , than if it was on solid , non-moving ground ..... so it will take off as long as it has the upper hand in power ratio ..... as well as helped by the crucial headwind of course & what not

to take off , thrust power has to be greater than resistance to the wheels . I understand that the wheels have no drivetrain as in a car has , but what you need to understand is that the conveyor IS the missing drivetrain of the wheels and thus causes it / simulates putting the wheels in reverse , while the thrusters are in drive / forward mode .

 

Thats true, the plane would take off because of the power of the engine pushing the plane forward, and the wheels are spinning in the same direction that the plane is moving, and the conveyor is spinning in the opposite direction. It would take more force than usual because it has to compensate for the extra drag brought on by the conveyor. I think people are getting caught up on this question because they are not understanding the physics of how a plane flys and are thinking in "car terms", that the wheels have a direct relationship to the engine which they dont. Also, the plane does not need a headwind to take off since it is moving it is creating lift by pushing air around the wings. Remenber, the question said nothing about wind. I also think people are thinking that the wheels on the plane are spinning in the direction of the conveyorm, but that was never mentioned in the original question, the conveyor is spinning in the opposite direction that the plane is moving. This is definitely a trick question, and this is what it is supposed to do, get people thinking.

 

one will think that a conveyor moving in the opposite direction of the plane's direction will make the wheels turn backwards , when in fact the conveyor needs to move in the same direction as the plane (forward) for the wheels of the plane to move backwards

so if the conveyor is making the plane move forward (cause of its rearward motion) then its that much easier to take off than on solid ground ) take a toy car and roll it on your hands to simulate the conveyor's direction and observe which way the wheels are going

mystery solved

 

and that is exactly it right there 6Pack. Since the conveyor is spinning in the opposite direction of the plane, the wheels would be moving forward. but the question is pretty vague in the first place, that people are not picking up that. the plane is not held in place by anything, there is no mention of wind at all. people need to read between the lines of the question to figure it out really. since the first answer many people think of "no", which is wrong, we have a hard time grasping that. since not all of us know how a plane works, we are thinking in car terms, which is the opposite of a plane.

 

 

The only way the plane would lift off in this scenario is a to be running against a head wind in the 20-30+ MPH range. There is no way the plane will take off if it is sitting still. If no air is moving over/under the wings, there will be no pressure differential to create lift. This is why you see steam catapults on our aircraft carriers and not treadmills.