Can the Plane Take-Off?

[vivek16]

Originally Posted by KenWittlief

Ok, I gotta fess up here and admit that when I took physics 101 in college I had to first unlearn 'roadrunner physics'

our thinking gets so ingrained to the things we experience personally, like driving a car or running on a treadmill, that we have a hard time doing thought experiments on things we are not familiar with (like flying a jet plane).

The question here makes you think the plane will not move at all, because our minds jump to something familiar - like a car on a dyno, or a person running on a treadmill.

Go back to the initial conditions: the plane is at rest, the runway is not moving.

The pilot hits the throttle and the plane has 30,000 pounds of thrust on its airframe. How on earth is the runway going to apply 30,000 pounds of thrust in the opposite direction to STOP the plane from moving? Through 3 wheels with greased roller bearings?

Lets say the plane gets up to 10mph like I said before. The runway is only allowed to move backwards at 10mph - to match the forward speed of the plane. There is no way the wheel bearings are going to have 30,000 pounds of friction while spinning at 20mph net speed! the wheels will have a few pounds of friction at the most, and the plane will continue to accelerate

and take off, pretty much like normal.

Picture the tablecloth trick, you yank the tablecloth out from under the dishes, and there is not enough force to pull them off the table.

'yanking the runway' out from under the plane is not going to have enough friction to overcome 30,000 pounds of thrust from the jet engines.

ok, before I read ken's post, I assumed that if they went canceling speeds then (like running on a treadmill) then the plane would stand still and Bernoulli's principle would have no effect. Now I see that the run way moving would have no effect whatsoever on the plane except making its wheels spin faster.

Cool, this would make for a very fun team debate

thanks, Vivek