Originally posted by Mini D
If an airplane were sitting on a conveyor belt and the conveyor belt instantly accelerated, the plane would barely move.
If you don't believe this, try pulling a table cloth out from below the place settings some time. That is completely acceleration dependent too and shows that you cannot add more acceleration to generate more force when friction is your only mode of transferring energy.
A plane would sit still and gradually start drifting backwards if a belt instantly accelerated below it... depending on how much friction could case the moment of the axle to drift backwards from perpendicular. The same is true of trying to keep the plane in one place with the engines running. You would have to be able to generate enough friction on the hub to move the plane's axle back to a perpendicular (straight down) moment.
No.
MiniD,
Answer the questions:
Here’s a story that illustrates my idea: (Note that the term wheels in this story refers to wheels and tires)
Identical triplets Al, Bob and Chuck buy three identical bush planes. Since they live in Alaska, all three brothers buy and install large balloon “tundra tires” and wheels. The wheels, planes and brothers are identical. All three planes will take off from a normal runway in exactly 100 feet and at exactly 50 mph. The brothers fly their planes to an air show in Wisconsin. At the air show Bob finds and buys a set of fantastic wheels. These wheels are exactly like the wheels he has on his plane in every way except they have half the mass. Their mass is distributed in the same proportion as the wheels that he plans on replacing. Al thinks Bob is silly and is content with his old wheels. Bob thinks that Al will eventually want a set, so he buys a second set to give to Al on their birthday.
Bob finds a buyer for his old heavy wheels and installs a set of his new lightweight ones. He loads the second set into his plane so that it is balanced just as it was before. Bob’s plane now weighs exactly the same as Al’s and Chuck’s, but its wheels have half the mass.
Meanwhile, Chuck runs into a magician who sells him a set of magic wheels. These wheels are exactly like the wheels he has on his plane in every way except they have no mass. Chuck installs his magic wheels. He loads the second set into his plane so that it is balanced just as it was before. Chuck’s plane now weighs exactly the same as Al’s and Bob’s, but its wheels have no mass.
When the brothers leave the air show they request a formation take off. They line up wing tip to wing tip and apply power at exactly the same time. All three planes weigh exactly the same and must hit 50 mph to lift off. When Chuck’s plane lifts off his wheels stop spinning instantly since they have no mass. Since they have no mass, they also have no rotational inertia. When Al’s plane lifts off his heavy wheels are spinning at 50 mph and have considerable rotational inertia. When Bob’s plane lifts off his half-weight wheels are spinning at 50 mph and have exactly half the rotational inertia as Al’s wheels.
Where did the rotational inertia and energy in Bob’s and Al’s wheels come from?
How did the rotational inertia and energy now stored in Bob’s and Al’s wheels affect the take off distance of their planes?
We know that Al’s plane will still take off in exactly 100 feet; where will Bob’s and Chuck’s planes take off?
