Something amazing to tell you concerning physics and motion

[cdcox]

Originally Posted by Joe Seahawk

Wheels do not matter when the jet is moved by the thrust of the jets.. the wheels and the treadmill are nearly irrelevant. This seems very simple to me.. Is something wrong with me?

No. There is something wrong with me for keep trying to come up with different explanations in an attempt to teach.

[Joe Seahawk]

Originally Posted by cdcox

No. There is something wrong with me for keep trying to come up with different explanations in an attempt to teach.

Where am I going wrong? if the treadmill moves at the backwards at the same speed the plane moves forward, I'm seeing the plane able to take off, although the wheels will be spinning twice as fast as non treadmill take off. I dunno, maybe I'm not understanding the question properly..

[orange]

Originally Posted by Joe Seahawk

Where am I going wrong? if the treadmill moves at the backwards at the same speed the plane moves forward, I'm seeing the plane able to take off, although the wheels will be spinning twice as fast as non treadmill take off. I dunno, maybe I'm not understanding the question properly..

The plane isn't actually moving forward. When you say "the wheels will be spinning twice as fast," no. The speed of the treadmill equals the speed of the wheels.

Since the plane isn't moving forward, there's no lift.

[Joe Seahawk]

Originally Posted by orange

The plane isn't actually moving forward.

.

Why?

[cdcox]

Originally Posted by Joe Seahawk

Where am I going wrong? if the treadmill moves at the backwards at the same speed the plane moves forward, I'm seeing the plane able to take off, although the wheels will be spinning twice as fast as non treadmill take off. I dunno, maybe I'm not understanding the question properly..

The problem statement (at least some versions of it) say the treadmill moves at the same rate as the wheels of the plane.

This statement causes a violation of Newton's second law.

[Joe Seahawk]

Originally Posted by cdcox

The problem statement (at least some versions of it) say the treadmill moves at the same rate as the wheels of the plane.

This statement causes a violation of Newton's second law.

Ah..

[prhom]

Originally Posted by cdcox

The problem statement (at least some versions of it) say the treadmill moves at the same rate as the wheels of the plane.

This statement causes a violation of Newton's second law.

It doesn't really violate it so much as complicate it by making it a dynamics problem where you have to account for rotational acceleration and momentum. Not a simple force balance.

[cdcox]

Originally Posted by prhom

It doesn't really violate it so much as complicate it by making it a dynamics problem where you have to account for rotational acceleration and momentum. Not a simple force balance.

This is the first idea that proposes at least a reasonable way to make it all hold together. I only wonder if the force needed to accelerate the wheels isn't coming from the treadmill motor rather than the jet engine? Unclear.

I'd calling it a night, and will do my best not to click on this thread at work tomorrow.

[prhom]

Originally Posted by Joe Seahawk

Where am I going wrong? if the treadmill moves at the backwards at the same speed the plane moves forward, I'm seeing the plane able to take off, although the wheels will be spinning twice as fast as non treadmill take off. I dunno, maybe I'm not understanding the question properly..

The plane wheels can never go faster than the treadmill because the original question said that the treadmill is designed to ALWAYS go as fast as the plane's wheels. Because of that statement we have to assume that as the plane accelerates and starts to gain on the treadmill, some control makes the treadmill accelerate and convert the plane's incremental thrust into ROTATIONAL acceleration and momentum in the wheels. By the way the problem is defined, the plane can never convert thrust into a higher incremental wheel speed versus the treadmill. THis has no basis in reality, and therefore cannot be proved by a simple experiment.
(At least it would require very complicated machinery to balance a model plane's thrust and treadmill acceleration)

[Joe Seahawk]

Originally Posted by prhom

The plane wheels can never go faster than the treadmill because the original question said that the treadmill is designed to ALWAYS go as fast as the plane's wheels. Because of that statement we have to assume that as the plane accelerates and starts to gain on the treadmill, some control makes the treadmill accelerate and convert the plane's incremental thrust into ROTATIONAL acceleration and momentum in the wheels. By the way the problem is defined, the plane can never convert thrust into a higher incremental wheel speed versus the treadmill. THis has no basis in reality, and therefore cannot be proved by a simple experiment.
(At least it would require very complicated machinery to balance a model plane's thrust and treadmill acceleration)

Apparently I misunderstood the question.. I thought the treadmill moved one direction in the same speed as the PLANE thrust propelled it in the opposite direction.

[prhom]

Originally Posted by Joe Seahawk

Apparently I misunderstood the question.. I thought the treadmill moved one direction in the same speed as the PLANE thrust propelled it in the opposite direction.

Yep, so did I for about an hour just look at the post history. I now feel compelled to make sure people catch that very important part of the question. The treadmill can adjust it's speed infinitely. THat changes everything.

[Joe Seahawk]

Originally Posted by prhom

Yep, so did I for about an hour just look at the post history. I now feel compelled to make sure people catch that very important part of the question. The treadmill can adjust it's speed infinitely. THat changes everything.

Well, than now it makes my head hurt.. I'm going to the epic fail thread!