OT riddle. v. Plane vs. Treadmill

[RedRocket1647545505]

Ok, first off, it amazes me the amount of stupidity on that site.

 

Here's the argument/riddle:

 

A plane is setting ON a treadmill (on it's wheels). There is no wind. The plane using it's jet engines, begins to accelerate forward. The treadmill begins moving backwards to match the planes speed. If they both keep accelerating, will the plane eventually take off?

 

/riddle.

 

Ok. It's overwhelming the amount of people on that site that believe that it WILL take off. You guys really should peak around on there to read some of the stupid reasons people give as to why it WILL take off.

 

Now, my reason for it NOT taking off:

 

In theory, the plane will have X amount of ground speed, however, ground speed doesn't create lift under the wings. You would need airflow over the wings to create lift. In order have airflow over the wings, you either have to have a headwind, or airspeed. As long as the plane is ON the treadmill, it will have no airspeed. No airspeed = no airflow over the wings = no lift.

 

Now, post up your opinions on this. And if you have time, and want to read something entertaining, mosey on over to OT and read up.

[Guest powers]

yea it won't fly. The plane is not moving just the wheels.

[Bgbdbn]

I say it will take off. The plane is not using its wheels for forward momentum. The jet engines are producing thrust against the atmosphere, therefor the wheels will just spin more rapidly than they otherwise would if it were not on a treadmill. The plane will get up to take off speed, just the wheels will be spinning at a much higher rate than they normally would. Action reaction, rearward thrust forward movement. The wheels just happen to be holding the plane up.

[Alex1647545498]

The plane's engines will push the treadmills forward because the engines don't power the wheels they push against the atomosphere. Doesn't even matter if the wheels move or not. So eventually it will fly.

[RedRocket1647545505]

I say it will take off. The plane is not using its wheels for forward momentum. The jet engines are producing thrust against the atmosphere, therefor the wheels will just spin more rapidly than they otherwise would if it were not on a treadmill. The plane will get up to take off speed, just the wheels will be spinning at a much higher rate than they normally would. Action reaction, rearward thrust forward movement. The wheels just happen to be holding the plane up.

 

 

You're forgetting one thing: friction. As long as the plane is ON the ground, it WILL be rolling backwards. Turn off the engines, but leave the treadmill on...the planes gonna roll backwards. If the plane is moving forward at 300mph, and the treadmill is pulling it backwards at 300mph, you have an air speed of 0(300-300). 0 airspeed = planes not going anywhere.

 

ground speed relative to treadmill = 600mph

ground speed relative to the ground outside of the treadmill = 0

airspeed = 0

 

next argument...

[Bgbdbn]

Maybe if it had its brakes locked up. But the wheels are spinning, they are not going to produce anywhere near enough friction to counter the thrust.

[RedRocket1647545505]

Maybe if it had its brakes locked up. But the wheels are spinning, they are not going to produce anywhere near enough friction to counter the thrust.

 

 

They will after the ineria equals out. Remember, the treadmill is matching the speed of the plane. Let's say that the plane is increasing it's speed by 1mph, every hour, that should be more than enough time for the wheels to catch up with the planes acceleration.

 

Think of it this way. If you put a model car on at treadmill, and turn on the treadmill, does the model car sit there spinning it's wheels in the same spot indefinitely? Sure, at first, it will spin it's wheels. But they will eventually stop, and the car will be moving backwards at the same rate that the treadmill is. Same goes for the plane.

[iwishiwascool]

You are correct austin. Thrust has nothing to do with it. A Jet car can create all the thrust it can, but unless it begins to create a pressure differential in the air flow over the wings aka lift, the plane isnt going anywhere.

 

 

And....

 

the first rule of OT....

[SPLN SUX]

An objects forward motion is defined by the object applying the force being exerted and the medium its being applied to.

 

So the answer here will come from following the force in both directions.

 

The force is coming from the propeller spinning.

 

The propeller is attached to the plane.

 

The force is being applied to the still air around the plane.

 

The air will move reward, and thus the plane forward.

 

The plane being on the treadmill has absolutly nothing to do with its forward motion and will only apply a small but insignificant amount of friction for the plane to overcome before actully moving forward. the only the plane WOULDNT move forward, would to be to spin the wheels fast enough to create as much force of friction, as the engines produce in thrust.

 

But the question here is what if we match speed for speed. So lets say the max speed of the plane is 200mph.

 

If you move the tread mill at 200mph, then apply full thrust to the engines, the plane will still move forward as long as the friction created by the wheels against the ground doesnt create a larger force than that of the engines thrust. This is almost impossible. So it is a safe bet to say the plane will move forward and eventully take off.

[Guest powers]

unless the rockey is only providing enough thrust to offset the friction that the weight of the plane on the wheels sitting on the treadmill. As long as the thrust and the treadmill are evenly matched the plane will not move forward at all, if it never moves forward it will never create lift under the wings.

[RedRocket1647545505]

A jet's not going to stay on a treadmill because thrust doesn't power the wheels, it pushes the entire aircraft through the atmosphere.. It's like putting wheels on a bottle rocket and expecting it to stay on there.

 

Ok. My next argument. Let's say you put some functioning wings on the SVX. Now, you drive it down the highway (where the road isn't moving) and at 88mph, it goes airborne. Now, because it is propelled by the wheels, it's obviously going to lose airspeed (<- keyword) when those wheels lose contact with the ground, and fall back down. The only difference between the plane's thrust and the car's thrust, is that the plane can move itself through the air, even after the wheels have left the ground, whereas the car can not. In our riddle, the plane has not left the ground, so it essentially behaves as the car would.

 

Now, take the same car, and put it on a treadmill that is going 88mph, backwards. Drive the car forward at 88mph. Is it going to fly? Nope.

 

And neither will the plane.

[RedRocket1647545505]

unless the rockey is only providing enough thrust to offset the friction that the weight of the plane on the wheels sitting on the treadmill. As long as the thrust and the treadmill are evenly matched the plane will not move forward at all, if it never moves forward it will never create lift under the wings.

 

 

Ding ding ding! We have a winner.

[SPLN SUX]

Pasted from abouve:

 

An objects forward motion is defined by the object applying the force being exerted and the medium its being applied to.

 

So the answer here will come from following the force in both directions.

 

The force is coming from the propeller spinning.

 

The propeller is attached to the plane.

 

The force is being applied to the still air around the plane.

 

The air will move reward, and thus the plane forward.

 

The plane being on the treadmill has absolutly nothing to do with its forward motion and will only apply a small but insignificant amount of friction for the plane to overcome before actully moving forward. the only the plane WOULDNT move forward, would to be to spin the wheels fast enough to create as much force of friction, as the engines produce in thrust.

 

But the question here is what if we match speed for speed. So lets say the max speed of the plane is 200mph.

 

If you move the tread mill at 200mph, then apply full thrust to the engines, the plane will still move forward as long as the friction created by the wheels against the ground doesnt create a larger force than that of the engines thrust. This is almost impossible. So it is a safe bet to say the plane will move forward and eventully take off.

 

God i love physics.

 

The End.

[Guest powers]

I didn't say speed for speed I said force for force. The plane MUST experience forward movement to create lift. If the 2 forces are equal the plane stays still.

[RedRocket1647545505]

Pasted from abouve:

 

An objects forward motion is defined by the object applying the force being exerted and the medium its being applied to.

 

So the answer here will come from following the force in both directions.

 

The force is coming from the propeller spinning.

 

The propeller is attached to the plane.

 

The force is being applied to the still air around the plane.

 

The air will move reward, and thus the plane forward.

 

The plane being on the treadmill has absolutly nothing to do with its forward motion and will only apply a small but insignificant amount of friction for the plane to overcome before actully moving forward. the only the plane WOULDNT move forward, would to be to spin the wheels fast enough to create as much force of friction, as the engines produce in thrust.

 

But the question here is what if we match speed for speed. So lets say the max speed of the plane is 200mph.

 

If you move the tread mill at 200mph, then apply full thrust to the engines, the plane will still move forward as long as the friction created by the wheels against the ground doesnt create a larger force than that of the engines thrust. This is almost impossible. So it is a safe bet to say the plane will move forward and eventully take off.

 

God i love physics.

 

The End.

 

 

In reality, could the plane out accelerate the treadmill's rearward pull, factoring in ineria? Sure it could. But that's not what the riddle is saying. We could also strap a Saturn 5 rocket to it and get it to fly, but the riddle isn't saying that either. What it's saying is, if you matched the planes forward speed, with the treadmill's rearward speed, would it take off?

[SPLN SUX]

I didn't say speed for speed I said force for force. The plane MUST experience forward movement to create lift. If the 2 forces are equal the plane stays still.

 

The plane using it's jet engines, begins to accelerate forward. The treadmill begins moving backwards to match the planes speed. If they both keep accelerating, will the plane eventually take off?

 

The word "Force" is not used anywhere in that question. Speed and Acceleration however were used... and both pretain to velocity. So to begin with, the questionis worded incorrectly if its supposed to mean force for force.

 

By saying, matching the planes speed, you say plane applys thrust to reach 10mph on solid ground, and turn the moving ground @ 10mph.

 

I understand the reasoning you have, but it just isnt right for the question typed.

[SPLN SUX]

Heres an analogy...

 

Put a car in Neutral and place it on slope that will allow it to roll at exactly 10mph forward. Now move the ground backwards at exactly 10mph... does the car stay stationary???

 

You know it wont. It only picked up some extra friction. It will slow down, but it wont stop. In theory, the wheel speed and vehicals velocity should be inverses of each other. So the wheel speed will double, but the vehicals velocity should halve.

 

The reason why the analogy works is because in both cases, no force is being applyed to the rearward moving ground. Two different types of forces are causing the vehicals velocity, but the results are the same.

[RedRocket1647545505]

The word "Force" is not used anywhere in that question. Speed and Acceleration however were used... and both pretain to velocity. So to begin with, the questionis worded incorrectly if its supposed to mean force for force.

 

By saying, matching the planes speed, you say plane applys thrust to reach 10mph on solid ground, and turn the moving ground @ 10mph.

 

I understand the reasoning you have, but it just isnt right for the question typed.

 

"The treadmill begins moving backwards to match the planes speed. (forward speed is inferred here)"

 

Nick, you're reading into the question waaaay too much. Take it for what it says.

[Guest powers]

there are too many variables to even figure out how the set up would be unless you said equal forces. Of course the plane could create more thrust than the treadmill but think about this, planes use 100% engine thrust to lift off. Would the treadmill counter that effort enough to keep the plane on the ground?

[SPLN SUX]

"The treadmill begins moving backwards to match the planes speed. (forward speed is inferred here)"

 

Nick, you're reading into the question waaaay too much. Take it for what it says.

 

Im reading the terms used and answering the quesiton accordingly. When it comes to physics, there is no leway on the terms.

 

Speed = a unit of measure, not a motion. MPH, KPH, etc.

Velocity = Speed + direction

Acceleration = Any change in the objects velocity. This includes speeding up or down, or any change of direction.

 

 

EDIT*

 

Heres where you fucked up....

 

If the plane is moving forward at 300mph, and the treadmill is pulling it backwards at 300mph, you have an air speed of 0(300-300). 0 airspeed = planes not going anywhere.

 

ground speed relative to treadmill = 600mph

ground speed relative to the ground outside of the treadmill = 0

airspeed = 0

 

next argument...

 

You basically said exactly what i read.

[RedRocket1647545505]

Heres an analogy...

 

Put a car in Neutral and place it on slope that will allow it to roll at exactly 10mph forward. Now move the ground backwards at exactly 10mph... does the car stay stationary???

 

You know it wont.

 

If you could somehow take potential energy out of the equation, then yes, it would stay stationary, relative to everything but the moving ground.

 

You're factoring in slope and potential energy into your answer. Obviously, the car would pickup speed on a downward slope. If the ground is stuck at 10mph moving backwards, while the car is accelerating PAST 10mph moving forwards, then of course the car is going to move. If you could somehow keep the car from accelerating due to potential energy (i.e level ground) then you take that variable out of the equation.

[RedRocket1647545505]

I'm calling Mythbusters right now.

[SPLN SUX]

look up

[JaSSon]

Do you realize just for bad-assed of a treadmill you would need to even attempt this?

 

Yes, if you had a jet at IDLE it would just free wheel on the treadmill and not go anywhere. But so long at the BRAKES are not engaged, the jet WILL move forward, I don't care how fast you move the treadmill The jet doesn't give a damn how fast the wheels or the ground (ground speed) is moving, because the jet engines push against the air, it will push the plane off the treadmill, and onto the tarmac for take off.

 

 

If you want to keep the plane on the ground, you would need a big ass fan behind (blowing towards the wings) the plane to keep air from flowing over the wings. Then it would have a killer ground speed, but relative airspeed wold remain zero.

[iwishiwascool]

Guys. The riddle is hypothetical anyway. Obviously if this were a real world situation the thrust of the engines would overcome the treadmills ability to compensate for the potential forward motion. That isnt what the riddle is saying.

 

If the treadmill could keep up, and the plane stayed stationary, would it take off? You would be a fool to say, yes.