Originally posted by: exdeath
Originally posted by: smack Down
Originally posted by: exdeath
Originally posted by: smack Down
Originally posted by: exdeath
Originally posted by: smack Down
Originally posted by: LukeMan
Originally posted by: smack Down
Originally posted by: LukeMan
aren't we suppose to neglect friction? If there is 0 Friction, then it doesn't matter what speed the treadmill is moving. Hell, with 0 Friction you could turn the plane engines off and set the treadmill to 100mph and the plane would move as fast as the treadmill. You need Friction for the wheels to have any affect on the plane. With 0 Friction, the Air is the only Force acting against you, which is easily overcome.
Even with zero friction between the wheel and axle the treadmill will still act on the plane.
how would the treadmill have any affect on the plane if the frictionless wheels/axles have no affect on the plane? You understand what grease and lube are used for right? -to decrease the amount of friction on the axle. With 0 Friction there is nothing pulling the plane in the same direction as the treadmill. Air would hold the plane in place, since it's the only force present.
To rotate a wheel one must apply energy. This energy does not come from friction but from torque.
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.
Simple wheel physics understood by mankind for over 10,000 years...
Smart guy we are talking about the friction between the axle and the wheel not the axle and the ground.
Wrong again, there is no friction between the wheel and the axle because they are rigidly connected, therefore the rotation of the axle is directly transfered to the wheel, and thus the ground.
But what you posted does show that the wheel acts on the plane and therefor the plane can't take off.
Yes the wheels act on the plane, just like it acts on the car when you push it by causing the car to resist your pushing due to friction against the ground being transfered laterally through the axle... but notice how can *still* push the 3,500 lb car with relatively little effort? Thats because the friction of the rotating wheels and axles is negligible. That is the whole point of a wheel in the first place, to reduce friction of an object in movement.
Most of the perceived effort is overcoming the inertia of the car at rest and the relatively little power from 1 person. Once the car is rolling, it takes little effort to keep pushing it on a flat level surface even with 1 person. A jet engine would be like pushing the car with 10,000 people. The resistance of the axles and wheels rotating against the ground won't stop them from moving the car. Pushing it at twice the speed won't increase the resistance of the wheels/axle by any percieved amount.
Wow you are a special kind of troll. Does it really matter if the wheel rotates freely at the axle or the axle rotates freely somewhere else. But I'm sure you already knew that and are just trolling. At least try and think a little.
You are right that when pushing the car it is hard at first because you need to accelerate the car AND apply a torque to the wheels.
Moving the car once accelerated (ideally) requires no additional force, but to accelerate the car more you have to act again on both the wheels and the body of the car.
Thank you for finally getting something. This isn't entirely true because there IS energy dissapation, but i'll ignore that...
By your saying it takes no additional force to keep the car moving once it is rolling, you just accepted that the bearings and wheels offer little resistance, otherwise the car would promptly skid to a halt. The majority of your argument was based on the idea that the rotational resistance of the wheels was enough to compensate for the forward thrust, and you just negated your own argument.
To accelerate the car more... you aren't accelerating more. You are increasing the velocity more, and you can do that with the same acceleration. Hold the pedal to one position, and the speedometer climbs. The force you apply is constant, the mass of the car is constant, thus the acceleration is constant and never changing. You never apply more or less acceleration, however with that constant acceleration, your velocity continues to climb. It is forward velocity that generates wing lift on the plane. The engines in the plane are full throttle from the moment you feel the kick in the seat until the time the plane stops climbing. The force is constant. The acceleration is constant. The mass of the plane is constant (ignoring fuel consumption and waste disposal). So the velocity increases, until you stop applying acceleration.
To get the car or the plane moving faster and faster, you do not need to apply additional force or acceleration. Just continue pushing it as hard as you have been, and provided you can keep up with it, it will continute going faster (until wind resistance comes into play and exponentially increases the power demands to apply that force)
Combine all these things together.
1) the trust of the engines is held constant at full power on take off, thus the acceleration is constant
2) the rolling resistance in the wheels is not sufficient to overcome the forward movement of the plane undergoing acceleration
3) the plane thus takes off on the conveyer
No, I am a physics major; my third major. You are the troll.
/thread
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