"Jim Macklin" wrote:
"alexy" wrote in message
news | "Jim Macklin"
wrote:
|
|
| b. If the treadmill was powered [and everything was
timed
| in sync] the belt would be accelerating rearward and the
| engine thrust would be pulling forward at the same rate,
| thus the airframe mounted wigs would have near zero
airspeed
| and lift and would not fly.
|
| Just to "set the hook" here, are you saying that it will
be possible
| to have the conveyer move backwards fast enough that the
plane remains
| still, even under full power, and with no brakes on?


sure, in our imaginary world. in the real world nobody will
try this so mechanical limitations are unimportant.

Okay, if that happens (the treadmill moving fast enough backwards to
offset the thrust of the plane's propulsion system), how fast will the
plane be moving forward? ?

Given your answer to that, how fast will the conveyor be moving, given
that the conveyer moves backward at the same speed at which the plane
moves forward?

Given your answer to that, what's to stop the plane from moving
forward?

The problem says the conveyer moves at the same speed as the plane.
How in the world can it, by moving the same speed as the plane,
prevent the plane's motion?

One more thought: I'm getting ready to get an emissions test on my
car. They put the back wheels on rollers, put it in gear, and run the
engine up until the indicated speed is, e.g., 30mph. This seems to be
the situation that you and a few others picture happening here. But in
my case, my car is NOT moving forward, so I would NOT say that the
roller under my wheels was moving at the same speed as my car. It is
turning at the same rate as my car's wheels, which is a whole 'nother
kettle of fish.
--
Alex -- Replace "nospam" with "mail" to reply by email. Checked infrequently.