Assuming the friction of the wheels was negligible, a jetpack would propel you based on the exhaust gases. This backward force would have an opposite reaction on you, meaning you move forward. In order to stop that forward motion there would have to be some sort of opposite force. A treadmill spinning the free spinning wheels beneath you would not provide that opposite force.
Plane on a Treadmill
- Thread starter Warder60
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Let me try this scenario:
Take a shopping cart, a treadmill and a length of rope. Tie the rope to one end of the shopping cart, like you were pulling it behind you. Put the cart on the treadmill and turn it on with the rope slacked. The cart would be stationary, the wheels of a shopping cart do not produce and power and are there only to spin as the pusher provides thrust.
So we have a cart on a moving treadmill, just sitting there. Now take the rope and begin to pull on the cart, does the cart remain stationary? No, the wheels spin at an increased rate based on the speed you pull and the speed of the treadmill. Since the wheels do not factor into how fast a shopping cart moves, the cart moves forward with an increased wheel speed.
Now, double/triple/quadruple the speed of the shopping cart as you are still pulling on the rope. Does the increased speed stop you from being able to pull the shopping cart forward? No, once again, the wheels spin faster and faster, (I'm assuming for this that the wheels won't fall apart), but no matter how fast they spin the cart will only move forward equal to the amount of force you are pulling the rope.
Now, if we replace the shopping cart with a plane, the plane only needs to be able to move forward to make air pass over the wings and therefore create lift. Since the plane/shopping cart will move forward how ever fast you pull it/however fast the jets propel it, the plane will take off as normal.
Take a shopping cart, a treadmill and a length of rope. Tie the rope to one end of the shopping cart, like you were pulling it behind you. Put the cart on the treadmill and turn it on with the rope slacked. The cart would be stationary, the wheels of a shopping cart do not produce and power and are there only to spin as the pusher provides thrust.
So we have a cart on a moving treadmill, just sitting there. Now take the rope and begin to pull on the cart, does the cart remain stationary? No, the wheels spin at an increased rate based on the speed you pull and the speed of the treadmill. Since the wheels do not factor into how fast a shopping cart moves, the cart moves forward with an increased wheel speed.
Now, double/triple/quadruple the speed of the shopping cart as you are still pulling on the rope. Does the increased speed stop you from being able to pull the shopping cart forward? No, once again, the wheels spin faster and faster, (I'm assuming for this that the wheels won't fall apart), but no matter how fast they spin the cart will only move forward equal to the amount of force you are pulling the rope.
Now, if we replace the shopping cart with a plane, the plane only needs to be able to move forward to make air pass over the wings and therefore create lift. Since the plane/shopping cart will move forward how ever fast you pull it/however fast the jets propel it, the plane will take off as normal.
Re: CyBookie - Plane on a Treadmill
Read my last post.
The lift comes as the jets/props move the plane. Do you agree that a jet engine produces thrust? If you agree with physics, what reaction does this thrust cause? You should've said the plane moving forward. What affect does the treadmill have on this force?
Read my last post.
Re: CyBookie - Plane on a Treadmill
Watch the little experiment video that was posted in this thread. The lift comes from the plane moving forward, just like it always does...
Watch the little experiment video that was posted in this thread. The lift comes from the plane moving forward, just like it always does...
Futility. I want that board Brian. I've got a scale aircraft model with a 7ft wingspan and 1hp engine. You provide the treadmill and I'll bring my model. And whoever said they are an ME, you must have not got it at ISU. You would have never made it though phy 223.
So in other words, no matter how fast the treadmill is turning the wheels will always turn faster by a rate equal to the speed of the rope. For example, if the rope is pulling at 20 mph and we turn the treadmill up to 50 mph the wheels will turn 70. so we turn the treadmill up to 70, but then the wheels turn 90, and so on.
Is this right?
Correct, the wheels are completely free spinning and have no impact one way or another on the thrust being produced by the plane. The wheels simply spin as fast as they have to in order to keep up with the treadmill.
I would really like to hear brianhos and isuno1fan among others' reaction to jbhtexas' example as well as my own. Tell me how it would be different.
Aircraft Carriers should get rid of the catapult and put little treadmills under each wheel of the jet. After the engines (for some of you wheels
are up to speed wham! we stop the treadmills suddenly and have instant flight.
are up to speed wham! we stop the treadmills suddenly and have instant flight.
Truthfully, I can see where the plane would fly...thus my "bingo" post. I'm enjoying playing devil's advocate..
Aircraft Carriers should get rid of the catapult and put little treadmills under each wheel of the jet. After the engines (for some of you wheels
Since they have no airspeed, would the planes go straight up like a helicopter when they got all that extra lift from the spinning tires?
Can I assume nobody is going to give an example to counter jbhtexas' or mine? Seriously, if someone could make a convincing argument the other way I'd love it, this sort of stuff is really interesting to me.
If the coefficient of friction with the wheels/treadmill is great enough, it would make it more difficult, but if it is negligible and the thrust of the plane can overcome it and move forward for a duration long enough, lift will be created and it will fly.
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