Physics Puzzle
- Thread starter chilluk
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2scoops0406
joe-90 said:
Yes it can it automatically adjusts it's speed to match yours.
joe-90 said:
Yes the conveyor supplies an equal and opposite amount of energy
joe-90 said:
joe-90 said:
No.
2
2scoops0406
That's the bit I don't understand, how does the velocity of the airflow increase without any external force? Newtons 1st law??
Don't get me wrong, I'm well prepared, indeed would be delighted to have a satisfactory explanation offered.
Don't get me wrong, I'm well prepared, indeed would be delighted to have a satisfactory explanation offered.
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BOB.DOLE
After trying out my new worm tunnel experiment conducted under stricked labortoriy conditions i can confirm i when back in time and i can confirm that we came from a worm.
The momentum of the aircraft moving through the air causes air to pass over the top and bottom of the wing. The shape of the wing means the air has further to travel over the top of the wing than the bottom. Since the airflow has to cover this distance in the same time as the airflow on the bottom of the wing (relative to aircraft speed), there is less pressure above the wing than below it. No momentum through the air = no airflow = no lift.
2
2scoops0406
Spark123 said:
So by this argument a mass of air has to accelerate over a curved surface (i.e. it has to "has further to travel over the top of the wing than the bottom"
But as Newtons law's states "An object at rest tends to stay at rest and an object in motion tends to stay in motion with the same speed and in the same direction unless acted upon by an unbalanced force."
What makes the air accelerate ?
I still don't understand. But... I still maintain a good explanation will do me fine !!
The engines make the aeroplane travel through the air at a velocity. The air is for arguament sake still. The wing passing through this air forces the air to flow above and below the wing. The shape of the top of the wing means the air has further to travel from the front to the back of the wing in the same time as the air has to travel along the same distance along the bottom of the wing. velocity = distance/time hence the velocity of the air travelling over the top of the wing will be higher than that of the air below the wing. P.S. I should really keep to sparkying, explaining aerofoils isn't my strongest subject!! Any aircraft engineers on here?
Are we going for the full 10 pages?
Are we going for the full 10 pages?
There's loads of websites on the net about this subject, 
I didn't know it was that well talked about,
MOD 2
feel free about time there was a decent debate in here
I didn't know it was that well talked about, MOD 2
feel free about time there was a decent debate in here
I've read and re-read, and I still say NO, the aircraft will not take off.
Joe's roller-skate argument is a very good one, and certainly made me stop to think, BUT it only works in that context due to the relationship between the strength one can apply with one's arm and the negligible weight of the roller-skate. If Joe was not pushing a roller-skate on a conveyor belt, but, say, a car, there would come a point at which it would be impossible to overcome the increased speed of the belt.
I'm assuming that for the purposes of this exercise, the "conveyor belt runway" is hypothetical, and therefore has no maximum acheivable speed, but that the plane's engines operate as they would in a real situation. In this case, the engines will increase until they get to their maximum power, the conveyor belt will have speeded up to match this, and nothing will happen (until the plane runs out of fuel).
Quite apart from all this, there is another reason why the plane will not leave the ground. This one, perhaps though, is just me being a pedant and picking apart the wording of the original scenario. We are told only the properties of the conveyor belt, that there is no wind, and that the pilot incrementally applies thrust to the engines. We are NOT told that at any point he rotates, or attempts to rotate, the aircraft, so it would not take off anyway!
Joe's roller-skate argument is a very good one, and certainly made me stop to think, BUT it only works in that context due to the relationship between the strength one can apply with one's arm and the negligible weight of the roller-skate. If Joe was not pushing a roller-skate on a conveyor belt, but, say, a car, there would come a point at which it would be impossible to overcome the increased speed of the belt.
I'm assuming that for the purposes of this exercise, the "conveyor belt runway" is hypothetical, and therefore has no maximum acheivable speed, but that the plane's engines operate as they would in a real situation. In this case, the engines will increase until they get to their maximum power, the conveyor belt will have speeded up to match this, and nothing will happen (until the plane runs out of fuel).
Quite apart from all this, there is another reason why the plane will not leave the ground. This one, perhaps though, is just me being a pedant and picking apart the wording of the original scenario. We are told only the properties of the conveyor belt, that there is no wind, and that the pilot incrementally applies thrust to the engines. We are NOT told that at any point he rotates, or attempts to rotate, the aircraft, so it would not take off anyway!
Spark123 said:
i agree entirely providing thrust is applied as the conveyor is started
the only relation to the plane is the friction created by the wheel bearings
even if you have a plane without the engines running the plane wont move with the conveyor rotating untill the friction is enough to to overcome the air resistance
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You are all missing the point and contradicting Newton. The wheels are a passive component and don't feature at all. Imagine the conveyor is made of ice and the wheels are ice skates. When the jet applies thrust then Newton tells us that there will be an equal and opposite reaction (which is why a rocket can fly in space). That reaction will cause the engines to move 'opposite' ie forward. The ice skates that the plane sits on will allow the conveyor to slip underneath without much friction. The plane will reach 180mph and take off. It matters not that the conveyor is slipping by at 360mph. You are confusing active and passive elements. Your logic is flawed.
Think Newton.
joe
Think Newton.
joe
the plane is a stationary mass the only way the convayor belt can effect the plane is via the wheels there is no other point of contact the only avalable way of tranfering the energy between the wheels and the plane is via the bearings
if the plane moves with the convayor belt it will only reach a speed where the air resistance = the friction of the wheel bearings
newton dosn,t come into this equasion as your assuming the full power of the conveyor is converted into force against the plane which it isnt
if the plane moves with the convayor belt it will only reach a speed where the air resistance = the friction of the wheel bearings
newton dosn,t come into this equasion as your assuming the full power of the conveyor is converted into force against the plane which it isnt
Aha !! So, for example, and assuming bearing friction was less than the air resistance, if the plane was just sat still and not thrusting, and then you fired up the conveyor belt, would the plane stay more or less still, and the wheels just spin underneath it ? Is that the key to all this ?
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