MercenaryForHire
Lifer
Jack up your car, take the brakes off, and spin a non-braked tire.
- M4H
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Mythbusters to take on "the plane and the treadmill" conundrum?
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Jack up your car, take the brakes off, and spin a non-braked tire.
- M4H
exdeath
Lifer
Absolutely wrong.
Friction tangent to the surface of the wheel and not directed toward the axis of rotation, is what induces torque in the first place.
An engine provides torque to an axle to rely on the friction of the wheel and its resistance to sliding against the pavement to push against the axle horizontally and move the car.
Notice when you apply torque to the axle, the surface of the wheels tries to rotate away from the direction of travel. The frictional force at the bottom of the wheels is in the direction of travel, and that is what moves a car.
The opposite is also true. By applying tangent friction to the surface of the wheel (simply by being in contact with the ground) and pushing on the axle, you create a torque in the axle.
Friction between the wheel and the ground is the same for both a car and a plane. In a car you apply torque in the axle to generate forward motion. In a plane you apply forward motion to the axle to create torque. Both the foward motion in the car, and the torque in the axles of the plane are cause by the tangent friction force where the wheel contacts the ground.
Simple wheel physics understood by mankind for over 10,000 years...
smack Down
Diamond Member
Smart guy we are talking about the friction between the axle and the wheel not the axle and the ground.
But what you posted does show that the wheel acts on the plane and therefor the plane can't take off.
exdeath
Lifer
How does the wheel act on the plane? In a car, the wheels rotate and push the car. In a plane, the plane pushes itself and the wheels rotate.
There is rolling resistance indeed, but nothing compared to the engine power or the rolling resistance the plane normally has to deal with. I see you never replied to my post addressing the magnitude of rolling friction and why it is negligible in this case (skateboard + treadmill + scale + pulley and weights)
The engines are rigidly coupled to the plane body. The treadmill is loosely coupled to the plane via free spinning bearings in the wheels. Most of the effort of the treadmill is wasted in adding rotational kinetic energy to the wheels, energy that does not translate to any linear forces on the plane with the exception of a very small resistance in the bearings.
To put this concept of coupling into perspective, place a object in a swimming pool. Have one person push the object in one direction by directly touching and pushing the object. You on the other hand have to counter their pushing efforts only by means of pushing against the water. You are not allowed to touch the object directly.
Will the water you push against the object have some effect? Sure it will. Will the person pushing the object care? Probably not.
AbsolutDealage
Platinum Member
Just out of morbid curiousity, how old are you smack Down?
MercenaryForHire
Lifer
OMG I GOT CRUSHED!
- M4H
WolverineGator
Golden Member
Think of it another way using the Space Shuttle as an example. Imagine the shuttle on the launch pad (=), with wheels down 🙂), and the vertical structure of the launch pad (||) turned into a conveyor belt with wheels 🙂) touching the conveyor belt (||):
||
||:*
||==
The premise is the conveyor belt turns as fast as the wheels. Now think what happens when you light up those engines. You introduce a force that causes wheels to turn as the shuttle 🙂*) moves forward. The conveyor (||) moves to keep up with the wheels, but it is no use. The thrust of the engines will move the craft no matter what's going on with the wheels 🙂).
||
||:*
||==
The premise is the conveyor belt turns as fast as the wheels. Now think what happens when you light up those engines. You introduce a force that causes wheels to turn as the shuttle 🙂*) moves forward. The conveyor (||) moves to keep up with the wheels, but it is no use. The thrust of the engines will move the craft no matter what's going on with the wheels 🙂).
WolverineGator
Golden Member
Also, the Bernoulli principle is incorrect in explaining how airplanes fly. The Bernoulli principle does help a little, but it's actually the Coanda effect that causes a plane to fly. Basically the wing "throws down" so much air as to equal the weight of the aircraft and hold it up in the air.
shortylickens
No Lifer
I already said it elseware but I know how much people love me, so I'll say it here too:
Chuck Norris grabs hold of it with his bare hands while running on the conveyor belt and throws the plane into flight.
Chuck Norris grabs hold of it with his bare hands while running on the conveyor belt and throws the plane into flight.
smack Down
Diamond Member
You can't just claim the thrust of the engines is so great it will take off.
You need to show that the force from the treadmill is not proportional to the speed of the treadmill or one of its derivatives. Anything else is just BS.
Cerpin Taxt
Lifer
troll troll troll troll troll troll troll troll troll troll troll troll troll troll troll troll troll troll troll troll
MercenaryForHire
Lifer
Then he roundhouse kicks the treadmill?
- M4H
A hudred people have already shown that, and you still don't beleive them, so what's the point of making it 101?
The speed of the two are the same, the WORK done by the 2 is FAR from equal since the thrust of the engines is acting on the whole plane and the friction from the treadmill is acting only on the wheels (ideally), or only slightly on the body (real world). Nobody here is gonna go into more depth with you becasue its not worth an hour of our time to prove it yet again only to have you still sit there with your finger in your ears screming out "hear no evil - see no evil - speak no evil".
The speed of the two are the same, the WORK done by the 2 is FAR from equal since the thrust of the engines is acting on the whole plane and the friction from the treadmill is acting only on the wheels (ideally), or only slightly on the body (real world). Nobody here is gonna go into more depth with you becasue its not worth an hour of our time to prove it yet again only to have you still sit there with your finger in your ears screming out "hear no evil - see no evil - speak no evil".
MercenaryForHire
Lifer
If a car is in neutral, and I rev the engine, does it move?
- M4H
AbsolutDealage
Platinum Member
But let's not forget the gravitational attraction of the plane to the treadmill.... I mean... that must be HUGE! The plane will never be able to overcome that... 😉
smack Down
Diamond Member
Wrong. You can't increase the rotation of a wheel with out applying a force.
AbsolutDealage
Platinum Member
Nope. You should have failed Physics I in highschool if you really think this, smack Down.
In a frictionless bearing, there will be no force transmitted from the treadmill to the body of the aircraft. None. Zip. Nada.
smack Down
Diamond Member
They would screw it up. They would create a test with a plane with really small wheels and the treadmill wouldn't be able to change speed enough to slow down the plane.
The experiment should be done on a plane that has very little thrust and is 90% wheels.
smack Down
Diamond Member
Ok lets go over this again.
If we remove the plane and just leave the wheels do you agree that they will not rotate?
Now if we put the plane back on the treadmill do you agree that the wheels will rotate?
What acted on the wheels to make them rotate in the second case. ANSWER: the mother F@$% plane. And if you see newtons 3 third law the wheel must act on the plane.
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