![]() |
If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
Thread Tools | Display Modes |
#81
|
|||
|
|||
![]() "The Flying Scotsman" wrote in message ups.com... Why dont we look at it from another direction !!! If the treadmill is moving at 60 MPH in one direction and the trust is set to pull 60 MPH in the oppisite direction, the plane would be neither moving forward or back. You are implying that because the treadmill is spinning the wheels at 60mph, that the treadmill is therefore exerting a force equal and opposite the thrust generated by the propellor neccesary to propel the plane forward at 60mph. That is incorrect. The force that the treadmill is capable of exerting on the mass of the aircraft through the wheels is negligible. you WILL NEED TO HAVE FORWARD MOMENTIUM to generate lift..... WOW, I must have missed that in ground school. You need airflow across the wings to generate lift. Which, because the plane is moving forward as stated in the question, is present. the only lift the wings will get is downwash from the prop. and i used the word STUPID not to offend anyone, but i am right in what i said about the aircraft. Apparently you are the only one that thinks so. |
#82
|
|||
|
|||
![]()
"The Flying Scotsman" wrote:
Why dont we look at it from another direction !!! If the treadmill is moving at 60 MPH in one direction and the trust is set to pull 60 MPH in the oppisite direction, the plane would be neither moving forward or back. Why. What's keeping it from moving forward if the thrust is set for a thrust that would normally move it forward at 60mph. And besides, you just said that the plane is moving neither forward nor backward. The statement of the problem is that the conveyor moves at the same rate and opposite direction as the plane. Since you say the plane is not moving, I guess neither is the conveyor. Do you really think that is what the poser of the question intended? g -- Alex -- Replace "nospam" with "mail" to reply by email. Checked infrequently. |
#83
|
|||
|
|||
![]()
On Sat, 04 Feb 2006 16:10:16 GMT, "Travis Marlatte"
wrote: As posed by the question, I agree that the belt is a distracter. However, it is not irrelevant as the thrust applied to achieve flying speed must overcome not only the normal tire rotation friction but twice that. That the plane will fly presumes that there is enough excess thrust to do just that. So long as the bearings don't melt or seize, there's not much (if any) extra "rotation friction" at double the normal takeoff speed. Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA) |
#84
|
|||
|
|||
![]()
It's surprising and refreshing
that this thread, with so many posts, hasn't (yet) degraded into a flame-fest. ![]() Amen to that! The Monk |
#85
|
|||
|
|||
![]()
"Doug" wrote:
The whole problem is confusing because "An airplane on a runway sits on a conveyer belt that moves in the opposite direction at exactly the speed that the airplane is moving forward." Moving forward with respect to what? The conveyor belt? (you gt the answer that it WONT take off), or the air? (you get the answer that it WILL take off). AMBIGUOUS!!! Yes, the problem could have been made uninteresting by removing any ambiguity. But as stated, it is very common (almost universal) to speak of movement of a terrestrial object with respect to the surface of the earth. If another frame of reference is intended, it is almost always specified. Two movements are mentioned in the problem. Is there any reason to suspect that one is movement relative to surface of the earth (the conveyor) and the other is movement relative to the first object? Why not th other way around, in which case the conveyor is just an ordinary runway? If you are not willing to resolve that ambiguity by assuming conventional frames of reference, you might as well assume that one is speaking of velocities relative to a solar system frame, in which case the plane may be going very very fast forward, backward, sideways, up, or down, depending on time of day and orientation relative to the earth. The problem makes a lot more sense assuming conventional use of "moving". -- Alex -- Replace "nospam" with "mail" to reply by email. Checked infrequently. |
#86
|
|||
|
|||
![]() "The Flying Scotsman" wrote in message ups.com... Why dont we look at it from another direction !!! If the treadmill is moving at 60 MPH in one direction and the trust is set to pull 60 MPH in the oppisite direction, the plane would be neither moving forward or back. You are implying that because the treadmill is spinning the wheels at 60mph, that the treadmill is therefore exerting a force equal and opposite the thrust generated by the propellor neccesary to propel the plane forward at 60mph. That is incorrect. The force that the treadmill is capable of exerting on the mass of the aircraft through the wheels is negligible. you WILL NEED TO HAVE FORWARD MOMENTIUM to generate lift..... WOW, I must have missed that in ground school. You need airflow across the wings to generate lift. Which, because the plane is moving forward as stated in the question, is present. the only lift the wings will get is downwash from the prop. and i used the word STUPID not to offend anyone, but i am right in what i said about the aircraft. Apparently you are the only one that thinks so. |
#87
|
|||
|
|||
![]()
All,
I read some of my posts in response to comments made about me. The spelling, punctuation, and grammar mistakes are all because of my blatant laziness, and excitement to get my post out. The comments I made about the gun and the crowd seemed a bit disturbing to me when I read through them. I should have picked a better example. Please do not take those comments as some subconscious plea. I have been through several hefty background checks in at least two states and the latest for the Department of Defense that went back to when I was a teenager. I admit that I was wrong initially about the answer to the question. After working through it via the posts, discussions with my friend, and my own reasonings, I changed my mind. I hope that in the future if you all see my posts you will not regard me as some crazy loon. I have been following r.a.s since late 2000 and think it is a priceless source of information and support. Many people helped my as I was going through my private pilot training, and I appreciate that. I hope that when I begin my instrument training that people will be just as kind and helpful. Thank-you. Jesse P.S. I could always chalk it up to the chemicals at work. Maybe my Mom dropped me on my head when I was a baby, you never know! |
#88
|
|||
|
|||
![]() Yes, the problem could have been made uninteresting by removing any ambiguity. But as stated, it is very common (almost universal) to speak of movement of a terrestrial object with respect to the surface of the earth. If another frame of reference is intended, it is almost always specified. Two movements are mentioned in the problem. Is there any reason to suspect that one is movement relative to surface of the earth (the conveyor) and the other is movement relative to the first object? Why not th other way around, in which case the conveyor is just an ordinary runway? If you are not willing to resolve that ambiguity by assuming conventional frames of reference, you might as well assume that one is speaking of velocities relative to a solar system frame, in which case the plane may be going very very fast forward, backward, sideways, up, or down, depending on time of day and orientation relative to the earth. The problem makes a lot more sense assuming conventional use of "moving". Yes, the frame of reference has everything to do with the answer ...and the riddle! Since the original post refers to an airplane taking off you should conclude that "air" (the atmosphere) has to be included in the mix and that an airplane does it's flying relative to the world/atmosphere. Then it is not unreasonable to assume that the riddle implies that the most logical reference frame is the planet and that the conveyor and the plane are moving in opposite directions with respect to that stationary observer. The only requirement then is that the airplane move fast enough to take off and that the conveyor move fast enough "backwards" to match the airplanes speed (only to satisfy the specified initial conditions even though the speed of the conveyor is entirely irrelevant to whether or not the airplane takes off.) It doesn't even matter if the wheels need a bearing job or if the plane is on skids or if the brakes are set. Either the engine generates enough thrust to overcome resistance and accelerate the plane to take off or it doesn't. |
#89
|
|||
|
|||
![]()
Kpi$LyLcEhRo wrote:
/snip/ PS:If you would like to know, I'm an engineer and an airline pilot! Jeeeeezus! Q: How do you know if there is an (airline pilot/engineer) at a party? A: Oh, he'll tell you! Happy Flying! Scott Skylane |
Thread Tools | |
Display Modes | |
|
|
![]() |
||||
Thread | Thread Starter | Forum | Replies | Last Post |
Passenger crash-lands plane after pilot suffers heart attack | R.L. | Piloting | 7 | May 7th 05 11:17 PM |
Navy sues man for plane he recovered in swamp | marc | Owning | 6 | March 29th 04 12:06 AM |
rec.aviation.aerobatics FAQ | Dr. Guenther Eichhorn | Aerobatics | 0 | October 1st 03 07:27 AM |
rec.aviation.aerobatics FAQ | Dr. Guenther Eichhorn | Aerobatics | 0 | September 1st 03 07:27 AM |
rec.aviation.aerobatics FAQ | Dr. Guenther Eichhorn | Aerobatics | 0 | August 1st 03 07:27 AM |