Doesn't matter. A treadmill cannot act to slow down (or speed up) a wheeled object on top of it.
i don't see how it can be put any simpler than this
people have made the arguement that wheels do not drive the plane
like planes with ski's or pontoons
well is doesn't really matter, in all cases the plane is moving forward to get air under the wings
lift has to do with air going under the wings, if you are stationary and its not a windy day how can there be air going under the wings to provide lift?
Who said anything about the treadmill causing the wheeled object to speed up or slow down ?
The given in the original question is that the treadmill moves the way I described, not that the treadmill causes the object's movement.
all we know about the conveyor belt is, that it will move, relative to the surroundings, at whatever speed the plane moves at, but in the opposite direction.
Why it moves, and how it does what it does, isn't relevant.
Neither is friction, or any of a thousand other possible variables. if they aren't part of the question then they aren't part of the answer.
It will take off.. I can't believe im going to do this again..
Imagine strapping on some roller skates and standing on a treatmill. Now if you grab on to the console at the front, and then turn on the treadmill, you will stay motionless with relativly little effort. Even if you increse the speed of the belt, it still takes very little effort to stay in one place, because the wheels compensate. Now grab a rope tied to the wall infront of you, and pull yourself forward. It CAN be done. Even if someone is speeding up the treadmill while you pull yourself forward, it CAN be done. The wheels on your skates will just speed up to compensate for the difference.
This is the basic idea of how a commercial 'jet' plane works. Its fan pulls air in the front and blows it out the back, using air, as the 'rope' to pull it forward.
The aircraft will move forward, and will generate lift under the wings as a result.
Basically this is a horribly worded question, which gives an impossible premise. The conveyor belt could NOT compensate for the wheel's movement, because the wheels themselves do not power the plane's forward movement.
I've already refuted the rope and the wall scenario several times..
The engines acting on the air is not the same as a rope on the wall, unless the wall is mounted on wheels and is also on the conveyor belt.
The engines are part of the plane, the plane cannot pull itself off the conveyor belt by pushing against itself, if the conveyor belt functions the way the the original question describes it.
and that's why it takes off....
Both my toy car example and the previously mentioned rope and rollerskates example are both perfectly valid demonstrations of this. The people that don't agree with this need to sit down and draw a FBD instead of trying to picture it in their head.
You might be right that it is implausible, but it isn't impossible, at least in theory.
It doesn't matter what is making the wheels move, and the wheels aren't making the conveyor belt move, some unmentioned but implied force is acting on the conveyor belt.
Maybe that's the cause for the confusion, some of you think the conveyor belt would only move becasue the wheels make it move, which wouldn't happen if the wheels are not driven themselves.
But that is not what the scenario is. We are not told why the conveyor does what it does, just that it does it.
You can't answer the question by just saying the conveyor belt wouldn't do that, that is discarding the question, not answering it.
can't take off.
no forward motion, no matter how much thrust. As stated in the OP the conveyor maintains the plane in a stationary position relative to the world/air.
If the plane were to move forward even an inch (relative to the world/air) then it breaks the premise in the scenario that the conveyor moves at exactly the same speed as the wheels, but opposite.
So in other words the plane can't move forward, if it did then the original statements of the postulate are incorrect because even if it moved a single inch the conveyor did not move at a speed equal and opposite to the wheels.
no forward motion, no matter how much thrust. As stated in the OP the conveyor maintains the plane in a stationary position relative to the world/air.
If the plane were to move forward even an inch (relative to the world/air) then it breaks the premise in the scenario that the conveyor moves at exactly the same speed as the wheels, but opposite.
So in other words the plane can't move forward, if it did then the original statements of the postulate are incorrect because even if it moved a single inch the conveyor did not move at a speed equal and opposite to the wheels.
the way i see it it comes down to 2 things
forward movement/thrust from the engines
and backward movement form the belt
if they match like what was said in the OP how can it go anyway let alone with out air going under the wings
the rollerskate example i don't think is very good you would be using something that is stationary to the ground to pull yourself forward, in the OP's question everything should be taking place on the treadmill
forward movement/thrust from the engines
and backward movement form the belt
if they match like what was said in the OP how can it go anyway let alone with out air going under the wings
the rollerskate example i don't think is very good you would be using something that is stationary to the ground to pull yourself forward, in the OP's question everything should be taking place on the treadmill
Wow - just wow. I can't believe this is still going on.
For all the people who still say it won't take off, please draw a free body diagram of the plane. Include all the horizontal forces. What force opposes the thrust of the engines to keep the plane stationary.
If you don't know how to draw a free body diagram (H.S. physics) then forget it. Your "intuition" isn't likely to give the right answer.
For all the people who still say it won't take off, please draw a free body diagram of the plane. Include all the horizontal forces. What force opposes the thrust of the engines to keep the plane stationary.
If you don't know how to draw a free body diagram (H.S. physics) then forget it. Your "intuition" isn't likely to give the right answer.
How does the conveyor move the plane backwards? If its able to do that it should be able to do that to a stationary plane also. However, if you turn the treadmill on, the plane will just sit there in its place. Now turn on the engines...what compensates for the unopposed force?
But if you drew a FBD you would realize the example results in exactly the same situation as if they were to use engines on a plane.
Soooo, you are in a seaplane aiming up river (against the current), you need 100 mph of airspeed to take off, the speed of the water is exactly whatever speed (in the opposite direction) you would be going if the water wasnt moving. (If you had enough thrust to go 50MPH, the water would move 50MPH the other direction).
How does the plane take off?
How does the plane take off?
The force is not unopposed. It is opposed by whatever force is making the conveyor belt move in the opposite direction.
This force, and the movement of the conveyor belt, are not static, they change to match the force being applied to the plane.
And the conveyor belt cannot "move the plane backwards" relative to itself. The backwards motion is only relative to the surroundings.
In the same way the plane can and does move forward, relative to the belt, but since the belt is moving in the opposite direction at the same speed, at all times, the motion of the plane relative to the surroundings is nil.
if you simply stand on a treadmill and don't walk forwards you would move backwards too
lets say you are on rollerskates just so we have the wheels in this scenerio, and you make no effor to move forward, sure the wheels may budge a bit when the treadmill is 1st turned on but with no force pushing forward you would also end up going backwards after it was turned on
same scenerio one good example of this is one of those stationary waves you see on cruse ships and other places, used so people can in a sense surf in place
"if you simply stand on a treadmill and don't walk forwards you would move backwards too "
Wouldn't you agree with me that actually you would not be moving, relative to the treadmill belt you are stanindg on, pretty obvious you would since you even say you are standing still.
I still think the big problem some people(not you) have is they can't grasp that motion is RELATIVE, not absolute.
The plane can be going like the blazes, relative to the conveyor, but standing still relative to everything else, including the air needed for lift.
Wouldn't you agree with me that actually you would not be moving, relative to the treadmill belt you are stanindg on, pretty obvious you would since you even say you are standing still.
I still think the big problem some people(not you) have is they can't grasp that motion is RELATIVE, not absolute.
The plane can be going like the blazes, relative to the conveyor, but standing still relative to everything else, including the air needed for lift.
We are assuming a frictionless case here. Any force on the wheels only causes the wheels to spin. No force is transferred to the body of the plane.
Oh come on people, this makes no sense. The plane would have to take off.
The belt is powered by itself - some lawnmower engine, whatever I don't care.
The plane is providing its own thrust - it is using air's inertia or resistance to change in sped to move forward.
When the plane's wheels begin to roll, the belt speeds up to match that speed in the opposite direction. Let's say the belt can travel infinitely fast.
Eventually, the plane will begin to move forward. the belt will continue to match the speed of the wheels, but the belt cannot keep the plane from moving forward, as it has no influence over on the plane's method of thrust.
The plane WILL move forward and take off normally, because the belt cannot slow its forward motion.
Someone said 'why can't you feel wind on your face while running on a treadmill?'
If you had a jet strapped to your butt and were using that for your forward thrust, you would feel wind and move forward, through a wall and into a tree or traffic or someother unfortunate end. Because you are using your feet for thrust and the treadmill can match that speed, you will never go anywhere.
The belt is powered by itself - some lawnmower engine, whatever I don't care.
The plane is providing its own thrust - it is using air's inertia or resistance to change in sped to move forward.
When the plane's wheels begin to roll, the belt speeds up to match that speed in the opposite direction. Let's say the belt can travel infinitely fast.
Eventually, the plane will begin to move forward. the belt will continue to match the speed of the wheels, but the belt cannot keep the plane from moving forward, as it has no influence over on the plane's method of thrust.
The plane WILL move forward and take off normally, because the belt cannot slow its forward motion.
Someone said 'why can't you feel wind on your face while running on a treadmill?'
If you had a jet strapped to your butt and were using that for your forward thrust, you would feel wind and move forward, through a wall and into a tree or traffic or someother unfortunate end. Because you are using your feet for thrust and the treadmill can match that speed, you will never go anywhere.
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