Yes, a treadmill moving backwards will move a tennis ball, a car, even a freewheeling plane backwards (assuming there's nothing like an engine or whatever acting on it.)

This is why a car coasts to a stop eventually, and given enough runway even a plane landing at 150mph will coast to a stop on its own.

What you have to realize, however, is the amount of force generated thus is the same whether the treadmill is moving at 1 mph, 10 mph, or 10,000 mph. Therefore, if the plane can generate enough force to overcome the 1 mph treadmill, it can generate enough force to overcome a 10,000 mph treadmill.

Again, I give the example of a plane generating just enough thrust to stay stationary on a backwards moving 10 mph treadmill. If we speed up the treadmill to 100mph, but maintain constant engine thrust, the plan will remain perfectly still.

 

Your logic I believe is slightly flawed.

Have you ever seen a seagull fly head first into the winds of a hurricane?

It does not work. I've actually seen seagulls fly backwards in a storm!

They don't generate enough energy to move them forward.

That is why planes do not cruise against the jet stream because it would require more fuel/throttle/energy to provide fwd motion.

That is also why planes actually GAIN time when flying with the jet stream.

Would you agree with me that a plane needs forward motion to generate lift?

How exactly can this plane generate lift on a treadmill going 10,000 mph based on your example?

 

THE TREADMILL HAS LITTLE-TO-NO SIGNIFICANCE IN THAT QUESTION!


Lift is generated by forward motion, which is generated by the thrust of the engines (jet/prop), which are in NO WAY tied to the treadmill.

Wheels are FREE SPINNING.

 

sea gulls flying in a hurricaine have nothing to do in this equation, it is not equal to a plane trying to take off on a treadmill. those are 2 completely different scenarios.

imagine a plane that could thrust 500mph but only needs 100mph to take off. now imagine a treadmill that moves 10,000 mph. now drop that plane on that treadmill, the forces of friction, gravity and treadmill speed will not stop that plane from eventually reaching its takeoff speed of 100mph. once that plane is in full boost, you could crank that treadmill up to any speed possible and it still wont stop that plane from taking off. it wont even really impede its motion no matter how fast you crank up the treadmill.
IBTL

 

So you are saying that if a plane needed 2100 lbs of thrust and generate a speed of 150 mph to take off on a coventional runway, that it could take off on a treadmill with the SAME amount of thrust even if the treadmill was moving the other way @ 100 mph?

 

That's the point - the plane DOES have forward motion. Because when the 737 plane is sitting on the 10,000 mph backwards treadmill, it can easily accelerate to its take-off speed of 150 mph forwards.

Again, as others have stated, the speed of the treadmill is complete irrelevant.

 

STOP LOOKING SO MUCH INTO THIS STUPID RIDDLE!

Forget about friction loss, heat loss, wind resistance, etc. It's just a simple trick question to see who has enough common sense to understand a very basic concept of motion. If this was a Physics test questions, I assure you the instructor would've written "assume zero wind resistance, friction loss, etc" on the question.

If you're going to include friction, wind, heat, etc, then forget it. You'll need to know what kind of plane it is and its drag coefficient, the material of the tires, their coefficients of both kinetic and static friction, the barometic pressure and humidity and how the tires react to it, etc etc etc. It'll be a 100-page long formula that would take the world's top scientists one year to write. And then....... you would have to do the same thing all over FOR A FRIGGIN' GIGANTIC PLANE TREADMILL THAT DOESN'T EXIST.

Come on guys, have some common sense. It's a yes or no question.

 

Yes! You get it.

 

YES! That's exactly correct.

A strong man can pull a jet. So lets say it takes about 200 lbs of force to move a jet along a runway. That 200 lbs is the same whether the jet is moving at 10 mph or 100 mph, or even 10,000 mph. Therefore that 2,100 lbs of thrust (more like 30,000 lbs of thrust for a 737) is reduced by the 200 lbs needed to overcome rolling resistance, but the rest of that thrust is pure acceleration for the plane, no matter if the treadmill/runway/jet is moving at 10 mph or 10,000 mph.

 

Disregard the seagull analogy and use the airplane analogy instead if it suits you. The fact remains, without forward momentum, you will not get the lift needed to get airborne.