are you saying the winch will or will not turn?
if it does then the cable will shorten and the object will travel towards it.
so doitall, are you saying the winch will not turn?
physics puzzle no.2
- Thread starter noseall
- Start date
are you saying the winch will or will not turn?
if it does then the cable will shorten and the object will travel towards it.
so doitall, are you saying the winch will not turn?
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It's not impossible to build a conveyor belt the size of a runway. If we assume for the sake of argument that it's possible to build a control system powerful and sophisticated enough to react instantly to the wheels rotation. Then what I believe would happen is that the thrust of the jets engines would overcome the traction of the tyres treads on the belt, and push the plane forwards. If the traction was too powerful to overcome, adding thrust would just increase the speed of the belt, which must be the equal and opposite reaction to the engines thrust that everyone is looking for. Does that make sense?
Nope !! not saying that.
If you winch the object, the speed of the wheels will be greater than the belt.
Yes sooey that is as maybe, but to make any headway on the belt the wheels will have to go faster than the belt.
For balski.
The speed would be measured at the point of contact between the two surfaces, for example two cars going up the M1 doing 100mph, one has small tyres and one has big tyres, the wheels with the small tyres will be turning faster than the big tyres, but the contact with the road will be the same speed, therefor if one wants to get in front the wheels has to go faster.
The rest is irrelevant
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Nope !! not saying that.
If you winch the object, the speed of the wheels will be greater than the belt.
so, the winch will overcome the movement of the belt regardless of the friction freewheeling going on below the wheeled object?
well obviously it will. there is no resistance 'cause the wheels are FREE- wheeling because they are free of FRICTION. and the winch will meet zero resistance and winch the object toward it.
now apply this to...........
I was agreeing with you, providing the tyres grip on the belt/runway was sufficient, the planes engines would just become a means of controlling the belt/runways speed.
Nope !! not saying that.
If you winch the object, the speed of the wheels will be greater than the belt.
so, the winch will overcome the movement of the belt regardless of the friction freewheeling going on below the wheeled object?
well obviously it will. there is no resistance 'cause the wheels are FREE- wheeling because they are free of FRICTION. and the winch will meet zero resistance and winch the object toward it.
now apply this to...........
Apply this to what
that the wheel will have to go faster to make headway on the belt.I agree
Traction is friction, or at least a result of it. So what do you mean?
V
vinty
Why are people still going on about this, the question was dealt with on a programme called 'Mythbusters' a couple of years ago.
A jet aircraft was put on a conveyor which was then switched on, the jet then applied forward thrust from it's engines, it took of easily. So that was the question answered.
A jet aircraft was put on a conveyor which was then switched on, the jet then applied forward thrust from it's engines, it took of easily. So that was the question answered.
What, they built a conveyor big enough, powerful enough, and responsive enough to counteract the force of the jets engines. Show us the video of that one.
Not denying that vinty.
The op added bait into the equation, which make all the difference to whether the plane can reach take off speed or not, and the answer is it cannot.
Lets try again, to take off the plane needs a land speed, to measure land speed its the distance the contact surface moves over the surface that's supporting it.
However in this case the surface is moving in the opposite direction at the same speed as the wheel, whilst the wheel is spinning like mad the surface is doing all the moving negating any forward motion by the wheel.
Make sense or shall we have another 20 pages.
with all due respect vinty, what has my question got to do with a jet aircraft and thrust from its engines?
It took me a while, and I imagine that most of the posts saying that the plane won't take off are getting confused, as I was, with regard to the wheels / conveyor issue, totally forgetting about the fact that there are hoofing great big engines providing thrust through the air.
The conveyor isn't an issue, because an planes forward thrust is via its engines, not it's wheels. If it was by its wheels, apart from the fact that it would be called a car with wings, then the standing still situation would be correct, and in fact a moot point as the question would be something that a 5 year old could answer.
The wheels would, in fact, be turning at the opposing speed of the conveyor, plus the forward speed that the planes engine thrust provided...... its fairly simple really, once you get over the conveyor not being an issue
The conveyor isn't an issue, because an planes forward thrust is via its engines, not it's wheels. If it was by its wheels, apart from the fact that it would be called a car with wings, then the standing still situation would be correct, and in fact a moot point as the question would be something that a 5 year old could answer.
The wheels would, in fact, be turning at the opposing speed of the conveyor, plus the forward speed that the planes engine thrust provided...... its fairly simple really, once you get over the conveyor not being an issue
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